JP2019054101A - Piezoelectric material, piezoelectric element, and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric material containing no lead and potassium and having a low dielectric loss tangent and an increased | d ₃₃ / d ₃₁ | ratio.
The solution of the above problem is a piezoelectric material comprising Na, Ba, Nb, Ti, Zr, Mn and made of a perovskite oxide, and t indicating the molar ratio of Ti to Nb is 0.08 ≦ t ≦ 0.15, z indicating the molar ratio of Zr to Nb is 0.01 ≦ z ≦ 0.04, β indicating the molar ratio of Ba to Nb is 0.08 ≦ β ≦ 0.17, α indicating the molar ratio of Na to Nb is 0.95 ≦ α ≦ 1.03, and m indicating the molar ratio of Mn to Nb is 0.0005 ≦ m ≦ 0. .0025.
[Selection] Figure 1

Description

  The present invention relates to a piezoelectric material, and more particularly to a piezoelectric element using a piezoelectric material not containing lead. The present invention also relates to an electronic device using the piezoelectric element.

ABO ₃ type perovskite metal oxides such as lead zirconate titanate (hereinafter referred to as “PZT”) containing lead are typical piezoelectric materials. Piezoelectric elements in which electrodes are provided on the surface of a piezoelectric material are used in various piezoelectric devices and electronic devices such as actuators, oscillators, sensors and filters.

  However, since PZT contains lead as an A-site element, the lead component in the discarded piezoelectric material is dissolved in the soil, and there is a possibility that the influence on the environment may be harmful. For this reason, various piezoelectric materials not containing lead (hereinafter referred to as “non-lead piezoelectric materials”) have been studied.

A typical lead-free piezoelectric material that is currently widely studied is a piezoelectric material containing potassium niobate. However, when synthesizing a piezoelectric material containing potassium, the raw material (for example, potassium carbonate) powder has high hygroscopicity, and it is difficult to accurately measure the raw material powder at a target molar ratio, which is difficult in industrial production. Further, the piezoelectric material containing potassium niobate (KNbO ₃ ) has deliquescence, and the piezoelectricity of the piezoelectric ceramic containing potassium niobate may deteriorate over time. Furthermore, in a piezoelectric material containing potassium niobate, the sequential phase transition temperature between tetragonal and orthorhombic crystals may be in the operating temperature range of the piezoelectric device (for example, from 0 ° C. to 80 ° C.). Since the piezoelectricity fluctuates remarkably around the successive phase transition temperature, there is a problem that the performance of the piezoelectric device fluctuates significantly depending on the operating temperature.

As an example of the lead-free piezoelectric material, there is a solid solution (hereinafter referred to as “NN-BT”) of sodium niobate (NaNbO ₃ ) and barium titanate (BaTiO ₃ ). Since NN-BT ceramics does not substantially contain potassium which causes difficulty in sintering and low moisture resistance, the piezoelectric characteristics hardly change over time. In addition, when NN-BT ceramics is used for a piezoelectric device, there is no phase transition of the crystal structure in the device operating temperature range (for example, from 0 ° C. to 80 ° C.). There is an advantage of almost none.

In the piezoelectric body, when a charge is applied in the polarization direction, the piezoelectric constant for the displacement in the polarization direction is d ₃₃ , and the piezoelectric constant for the displacement in the in-plane direction of the piezoelectric body orthogonal to the direction of the displacement of the piezoelectric constant d _33. constant expressed as _{d 31.}

In Patent Document 1, a lead-free piezoelectric material (bismuth sodium titanate-based) having | d ₃₃ / d ₃₁ | of 3 or more is used for a specific piezoelectric element, so that it is unnecessary due to d ₃₁ compared to PZT. There is a disclosure that it is possible to suppress vibration.

However, d ₃₃ of the bismuth sodium titanate-based piezoelectric material disclosed in Patent Document 1 is limited to 80-160 pC / N, and there is a problem that it does not reach 200 pC / N of PZT.

On the other hand, Non-Patent Document 1, sodium niobate lead-free - barium titanate - calcium zirconate _{(NaNbO 3} -BaTiO ₃ -CaZrO ₃₎ composition system is disclosed, in certain component _{ratio, d 33} is It has been shown to exceed 200 pC / N.

JP 2011-199206 A

Ruzhong Zuo et al., Applied Physics Letter, 2016, 109, 022902.

However, the dielectric loss tangent at room temperature in the composition of 0.875 (NaNbO ₃ ) -0.1 (BaTiO ₃ ) -0.025 (CaZrO ₃ ), which shows a good piezoelectric constant in Non-Patent Document 1, exceeds 0.02. Yes. When the dielectric loss tangent of the piezoelectric material is larger than 0.02, the power consumption when used as a piezoelectric element is remarkably increased or the efficiency is remarkably lowered.

The present invention has been made to solve such a problem, and does not contain lead and potassium, has a high value of | d ₃₃ / d ₃₁ |, and a low value of dielectric loss tangent, and has a low value of NNBT-based lead-free piezoelectric material. The material is provided. The present invention also provides a piezoelectric element and an electronic device using the piezoelectric material.

The piezoelectric material of the present invention that solves the above problems is
A piezoelectric material comprising Na, Ba, Nb, Ti, Zr, Mn and made of a perovskite oxide,
T indicating the molar ratio of Ti to Nb is 0.08 ≦ t ≦ 0.15,
Z indicating the molar ratio of Zr to Nb is 0.01 ≦ z ≦ 0.04,
Β indicating the molar ratio of Ba to Nb is 0.08 ≦ β ≦ 0.17,
Piezoelectric material wherein α indicating the molar ratio of Na to Nb is 0.95 ≦ α ≦ 1.03, and m indicating the molar ratio of Mn to Nb is 0.0005 ≦ m ≦ 0.0025 It is.

A piezoelectric element according to the present invention is a piezoelectric element having a piezoelectric material portion and an electrode,
The piezoelectric material constituting the piezoelectric material portion is the above-described piezoelectric material.

  An electronic apparatus according to the present invention includes the above-described piezoelectric element.

According to the present invention, by adding an appropriate amount of the Mn component, it is possible to provide a novel piezoelectric material in which the dielectric loss tangent is suppressed and the | d ₃₃ / d ₃₁ | ratio is increased. In addition, the present invention can provide a piezoelectric element and an electronic device using the piezoelectric material.

  Moreover, since the piezoelectric ceramic of the present invention does not use lead and potassium, the load on the environment is small, and it is excellent in terms of moisture resistance and storage stability.

It is the schematic which shows one Embodiment of a structure of the piezoelectric element of this invention. 1 is a schematic cross-sectional view showing an embodiment of a configuration of a multilayer piezoelectric element of the present invention. It is the schematic which shows one embodiment of the electronic device of this invention. It is the schematic which shows one embodiment of the electronic device of this invention. It is the schematic which shows one embodiment of the electronic device of this invention. It is a diagram showing the relationship between the Mn content and the value of the dielectric loss tangent | Examples 11-13 and in the piezoelectric element of Comparative Example 1 of the present invention _{| d} 33 _/ d _31. Is a diagram showing the relationship between the Zr amount value _{| d} 33 _/ d ₃₁ | of the piezoelectric elements of Examples 21 to 23 and 31 to 33 and Comparative Examples 21 and 31 of the present invention. It is a polarization-electric field hysteresis curve in the piezoelectric elements of Examples 21 to 23 and Comparative Example 2 of the present invention.

  Hereinafter, modes for carrying out the present invention will be described.

  The present invention provides a lead-free piezoelectric material having a basic structure of NN-BT and a good mechanical quality factor and good piezoelectricity. The piezoelectric material of the present invention can be used for various applications such as capacitors, memories, and sensors by utilizing the characteristics as a dielectric.

The piezoelectric material of the present invention has the following characteristics.
(Feature 1) Contains Na, Ba, Nb, Ti, Zr, and Mn.
(Feature 2) It consists of a perovskite oxide.
(Feature 3) t indicating the molar ratio of Ti to Nb is 0.08 ≦ t ≦ 0.15.
(Feature 4) z indicating the molar ratio of Zr to Nb is 0.01 ≦ z ≦ 0.04.
(Feature 5) β representing the molar ratio of Ba to Nb is 0.08 ≦ β ≦ 0.17.
(Feature 6) α indicating the molar ratio of Na to Nb is 0.95 ≦ α ≦ 1.03.
(Feature 7) m indicating the molar ratio of Mn to Nb is 0.0005 ≦ m ≦ 0.0025.
(Characteristic 8) More preferably, the piezoelectric material contains 0.97 or more and 1.03 or less of Ca in molar ratio with respect to Zr.

  Each of these features will be described in detail below.

(Feature 1)
The piezoelectric material of the present invention contains Na, Ba, Nb, Ti, Zr, and Mn. More preferably, the piezoelectric material also includes Ca.

When the piezoelectric material contains Na, Ba, Nb, Ti, and O as main components at the same time, the piezoelectric constant of the piezoelectric material is increased, and each of the device operating temperature ranges (for example, from 0 ° C. to 80 ° C.) Variations in characteristics can be reduced. In addition piezoelectric material that contains Ca, the piezoelectric constant d ₃₃ is further increased by.

When the piezoelectric material contains a small amount of Zr and a small amount of Mn in addition to the main components of Na, Ba, Nb, Ti, and O, the | d ₃₃ / d ₃₁ | value of the piezoelectric material can be as large as 3 or more. . With this configuration, the dielectric loss tangent becomes less than 0.02 (2%) when an alternating voltage of 1 kHz is applied at room temperature, for example. Further, when Ca is contained, a piezoelectric material having a larger value of | d ₃₃ / d ₃₁ | value of 3.5 or more can be obtained.

Furthermore, the piezoelectric constant | d ₃₃ / d ₃₁ | is more preferably 4.0 or more from the viewpoint of suppressing unnecessary vibration caused by d ₃₁ .

(Feature 2)
The piezoelectric material is made of a perovskite oxide. The same applies when the piezoelectric material contains Ca. Since the piezoelectric material is made of a perovskite oxide, the piezoelectric material of the present invention exhibits a large piezoelectric constant.

  This crystal structure is preferably a so-called main phase in which the perovskite structure accounts for a majority of the whole, and more preferably a single phase consisting only of the perovskite structure. For example, if there are many tungsten bronze structures, the piezoelectric constant may be significantly reduced.

In the present invention, the perovskite type metal oxide means a perovskite type structure (perovskite type) ideally having a cubic structure as described in Iwanami Physics and Chemistry Dictionary 5th edition (issued on February 20, 1998). A metal oxide having a structure). A metal oxide having a perovskite structure is generally expressed by a chemical formula of ABO ₃ . In the perovskite type metal oxide, the elements A and B occupy specific positions of unit cells called A sites and B sites in the form of ions, respectively. For example, in the case of a cubic unit cell, the A element is located at the apex of the cube and the B element is located at the body center. O element occupies the center of the cube as an anion of oxygen. The cubic A-site element is 12-coordinate and the B-site element is 6-coordinate. When the A element, the B element, and the O element are slightly coordinate-shifted from the symmetrical position of the unit cell, the unit cell of the perovskite structure is distorted to become a crystal system such as tetragonal, rhombohedral, or orthorhombic.

  For example, in the case of a tetragonal crystal, the only four rotation axis directions are defined as c-axis, and two crystal axes perpendicular to and perpendicular to each other are defined as a-axis and b-axis. The length of each unit cell in the axial direction is represented by c, a, b (= a).

  In the main component of the material of the present invention, Na and Ba are located at the A site, and Nb, Ti and Zr are located at the B site, but the Na / Nb ratio is intentionally smaller than 1 and the Ba / Ti ratio is 1 It may be larger. Even if the amount ratio of the A-site element, B-site element, and oxygen element in the entire metal oxide is not necessarily 1: 1 to 3, if the perovskite structure is the main phase accounting for 90% or more, the present invention Included in the range. More preferably, it is a single phase that occupies substantially all of the oxide having a perovskite structure.

  Whether the oxide has a perovskite structure can be determined from, for example, measurement results of X-ray diffraction and electron beam diffraction on a piezoelectric material.

(Feature 3, 5, 6)
The main element other than oxygen in the piezoelectric material is occupied by Na, Ba, Nb, Ti, Zr, and Mn, so that the improvement of the | d ₃₃ / d ₃₁ | value, which is the aim of the present invention, can be obtained. A sufficient suppression effect is obtained. However, for the purpose of adjusting other physical properties of the piezoelectric material, other metal elements may be added as long as the effects of the present invention are not impaired.

Here, the main component constituting the piezoelectric material of the present invention is obtained by adding ferroelectric barium titanate to sodium niobate which is an antiferroelectric material. When t or β indicating the amount of barium titanate with respect to sodium niobate is larger than 0.15 or 0.17, the Curie temperature is greatly lowered, for example, to 80 ° C. or less. On the other hand, when t or β is less than 0.08, the piezoelectric constant and the mechanical strength are lowered. Therefore, when the range is 0.08 ≦ t ≦ 0.15 and 0.08 ≦ β ≦ 0.15, a high Curie temperature and good piezoelectricity can be obtained. Furthermore, when in the range of 0.09 ≦ t ≦ 0.12 and 0.09 ≦ β ≦ 0.12, a Curie temperature of 190 ° C. or higher and a piezoelectric constant | d ₃₁ | of 50 pm / V or higher are obtained. The possibility that the piezoelectric performance is deteriorated by heat in the device manufacturing process is low, which is more preferable.

The piezoelectric constant d ₃₁ is generally expressed as a negative value, but the absolute value is expressed below.

(Features 4, 7, 8)
In the piezoelectric material of the present invention, z indicating the molar ratio of Zr to Nb is in a range of 0.01 ≦ z ≦ 0.04, that is, Zr is 4 mol% or less of the elements occupying the B site. By occupying, the dielectric constant at room temperature increases and the piezoelectric performance improves. As the amount of Zr increases, the c / a ratio of the perovskite structure decreases and the anisotropy of the crystal structure changes.

  In addition, when the spontaneous polarization of the piezoelectric material of the present invention is pinned, Zr can reduce the pinning of the spontaneous polarization. When pinning is reduced, the residual polarization value decreases or the coercive field decreases in a polarization-electric field hysteresis curve close to saturation. When Zr exceeds 4 mol% of the B site, the resistivity decreases.

When m showing the molar ratio of Mn to Nb is in the range of 0.0005 ≦ m ≦ 0.0025, the piezoelectric material contains Mn, so that resistivity, piezoelectric constant, electromechanical coupling coefficient, mechanical quality factor, Young The rate and density can be increased. In particular, by including Mn in the above range in the piezoelectric material of the present invention, the effect of suppressing the dielectric loss tangent at room temperature and the effect of improving the | d ₃₃ / d ₃₁ | value can be obtained as compared with the case where Mn is not included.

  The Mn is contained in the piezoelectric material, and exists at the grain boundary of the perovskite structure A site or B site or the perovskite structure crystal grains made of Na, Ba, Nb, Ti, Zr, and O.

  When Mn is located at the A site, there is an effect of compensating for defects in the crystal structure.

  When Mn is located at the B site, a defect dipole is formed and an internal electric field is generated.

  Even if Mn is located at any site, the effect of the present invention can be obtained. Mn may be contained in both the A site and the B site.

  At least a part of Mn may be present at the grain boundary. Mn present at the grain boundaries is preferably present as an oxide. The presence of a part of Mn biased toward the grain boundary can suppress the pores, increase the mechanical quality factor, and increase the Young's modulus. In addition, the presence of a part of Mn at the grain boundary reduces the grain boundary friction and is expected to make the material harder.

  The distribution of Mn in the sample and the occupied sites in the crystal can be evaluated with an electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction, Raman scattering, and a transmission electron microscope.

  When Mn exists only at the A site, since the Mn ion is smaller than the Na ion or Ba ion, the volume of the unit cell is reduced.

  When Zr exists only at the B site, since the Zr ion is larger than the Nb ion or Ti ion, the volume of the unit cell increases.

  When Ca is present only at the A site, since the Ca ions are smaller than the Ba ions, the unit cell volume decreases.

  When the above states are realized at the same time, the above effects appear in a superimposed manner.

  However, excessive addition of Ca may significantly reduce the Curie temperature and the successive phase transition temperature, and therefore it is preferable to contain Ca in a molar ratio of 0.97 to 1.03 with respect to Zr.

  The volume of the unit cell can be calculated from the angle of each diffraction peak in the X-ray diffraction measurement.

As the amount of Zr increases, the c / a ratio of the perovskite structure decreases and the anisotropy of the crystal structure changes. Although it is conceivable that the value of | d ₃₃ / d ₃₁ | decreases as c / a decreases, in the material of the present invention, an increase in | d ₃₃ / d ₃₁ | value can be obtained by adding Zr. This is considered to be influenced by the ease of displacement of atoms in the twist direction with respect to the c-axis.

By simultaneously adding Ca in addition to Zr and Mn, the above effect appears in a superimposed manner, and an increase in | d ₃₃ / d ₃₁ | value can be expected.

(Curie temperature)
The Curie temperature is a temperature at which the piezoelectricity of the piezoelectric material disappears above that temperature. In this specification, the temperature at which the capacitance becomes maximum near the phase transition temperature between the ferroelectric phase and the paraelectric phase is defined as the Curie temperature. For example, the capacitance at 1 kHz can be measured and determined by an impedance analyzer (4194A manufactured by Keysight Technologies (former Agilent Technologies)) while changing the temperature of the piezoelectric material provided with the electrode.

  When evaluating the Curie temperature of a single piezoelectric material having no electrode, an X-ray diffraction image of a sample obtained by pulverizing and pulverizing the piezoelectric material is measured, for example, in the range of room temperature to 300 ° C. The temperature at which the phase transition from the conductive structure to the paraelectric structure occurs can be regarded as the Curie temperature.

  The Curie temperature of the piezoelectric material of the present invention is preferably 235 ° C. or higher and 400 ° C. or lower. When the piezoelectric material has a Curie temperature of 235 ° C. or higher, the piezoelectric constant of the piezoelectric material does not decrease even when a heating process such as a thermocompression bonding process of a resin is performed when an element is processed after the piezoelectric material is polarized. Therefore, it is preferable. On the other hand, when the Curie temperature of the piezoelectric material is 400 ° C. or lower, the polarization treatment of the piezoelectric material becomes easy.

(Piezoelectric constant)
The piezoelectric constant is an amount indicating the degree of displacement (extension, contraction, shear) of the piezoelectric material when a voltage is applied to the piezoelectric material. For example, the piezoelectric constant d ₃₁ is proportional to the contraction (extension) displacement in the direction orthogonal to the polarization direction when a voltage is applied in the polarization direction of the piezoelectric material (usually the direction in which the voltage is applied during the polarization process). The coefficient, that is, the amount of displacement per unit voltage. Conversely, it can also be defined as the amount of charge induced when stress is applied to the material.

  The piezoelectric constant of the piezoelectric material can be obtained by calculation from the measurement results of the resonance frequency and antiresonance frequency obtained using a commercially available impedance analyzer, based on the standard of the Japan Electronics and Information Technology Industries Association (JEITA EM-4501). In this specification, unless otherwise specified, measurement of the piezoelectric constant at room temperature, for example, at 25 ° C. is intended. This measurement method is called a resonance-antiresonance method.

  In addition to the resonance-antiresonance method, the piezoelectric constant can be calculated by measuring a displacement amount when applying a voltage or measuring an induced charge amount when applying a stress. From the viewpoint of good vibration characteristics, the piezoelectric constant d33 is preferably 200 pm / V or more.

(Ti, Nb ratio)
The molar ratio t of Ti to Nb contained in the piezoelectric material is preferably 0.08 ≦ t ≦ 0.15. By being 0.08 or more, crystallization of the piezoelectric material is promoted, and mechanical strength and density required for mounting the piezoelectric material on an electronic device can be obtained. On the other hand, when t is 0.15 or less, the characteristics of sodium niobate as a main component are emphasized, and a Curie temperature of 190 ° C. or higher and a piezoelectric constant | d ₃₁ | of 50 pm / V or higher are obtained. A more preferable range of t is 0.09 ≦ t ≦ 0.12.

(Pb component, K component)
The Pb component and K component contained in the piezoelectric material are preferably less than 1000 ppm in total.

  More preferably, the Pb component contained in the piezoelectric material is less than 500 ppm, and the K component is less than 500 ppm. Even more preferably, the sum of the Pb component and the K component is less than 500 ppm.

  If the amount of the Pb component contained in the piezoelectric material of the present invention is suppressed, the influence of the Pb component released into the environment when the piezoelectric material is left in water or soil can be reduced.

  When the amount of the K component contained in the piezoelectric material of the present invention is suppressed, the moisture resistance of the piezoelectric material and the efficiency during high-speed vibration are increased.

(Dielectric loss tangent)
The dielectric loss tangent of the piezoelectric material of the present invention at room temperature is preferably 0.02 or less (2% or less). When the dielectric loss tangent at room temperature is 0.02 or less, the power consumption of a piezoelectric element or electronic device using the piezoelectric material of the present invention can be suppressed. More preferably, the dielectric loss tangent at room temperature is 0.013 or less (1.3% or less), and even more preferably 0.01 or less (1% or less).

  The dielectric loss tangent of the piezoelectric material at room temperature can be measured, for example, at a frequency of 1 kHz using a commercially available impedance analyzer after applying an electrode to the piezoelectric material.

(Piezoelectric material manufacturing method)
The piezoelectric material of the present invention is characterized by its constituent components, composition ratio, and crystal structure, and there is no particular limitation on the production method, and the piezoelectric material of the present invention can be obtained by a general inorganic oxide synthesis means. .

  Hereinafter, an example of a desirable manufacturing method will be described.

  In order to obtain a piezoelectric ceramic which is an embodiment of the piezoelectric material according to the present invention, a molded body before firing is produced. Here, ceramics represents a so-called polycrystal, which is an aggregate (also referred to as a bulk body) of crystal particles whose basic component is a metal oxide and is baked and hardened by heat treatment. Those processed after sintering are also included in ceramics. The said molded object is the solid substance which shape | molded raw material powder.

  The raw material powder is preferably higher in purity.

  Examples of the metal compound powder that can be used as the raw material powder include Na compounds, Ba compounds, Ti compounds, Nb compounds, Mn compounds, Zr compounds, and composite compounds thereof.

  Usable Na compounds include sodium carbonate and sodium niobate.

  Examples of usable Ba compounds include barium oxide, barium carbonate, barium oxalate, barium acetate, barium nitrate, barium titanate, and Ba—Nb composite calcined powder.

  Examples of Ca compounds that can be used include calcium oxide, calcium carbonate, calcium oxalate, calcium acetate, calcium titanate, calcium zirconate, and calcium zirconate titanate.

  Examples of Ti compounds that can be used include titanium oxide and barium titanate.

  Examples of Nb compounds that can be used include niobium oxide and sodium niobate.

  Usable Mn compounds include manganese oxide (IV), manganese oxide (II), manganese oxide (II), manganese carbonate (II), manganese acetate (II), manganese nitrate (II), manganese oxalate (II) Etc.

  Zr compounds that can be used include zirconium oxide, barium zirconate, barium zirconate titanate, calcium zirconate and the like.

In order to form the piezoelectric material of the present invention, desirable raw material powder combinations include sodium niobate (NaNbO ₃ ) calcined powder, barium titanate (BaTiO ₃ ) calcined powder, barium carbonate and niobium oxide mixed. Examples of the calcined Ba—Nb composite calcined powder, manganese oxide powder (for example, Mn ₃ O ₄ , MnO ₂ ), zirconate compounds (for example, calcium zirconate (CaZrO ₃ ), barium zirconate (BaZrO ₃ )) can be given. With this combination of raw material powders, crystallization proceeds at a relatively low temperature, for example, 1300 ° C. or lower, and the effect of the present invention of a high Curie temperature is easily obtained. The raw material mixed powder is preferably used for molding after calcining at a maximum temperature of 800 ° C. to 1000 ° C.

  Examples of the method for forming the raw material mixed powder include uniaxial pressing, cold isostatic pressing, warm isostatic pressing, cast molding, and extrusion molding. When producing a molded object, it is preferable to use granulated powder. When a molded body using the granulated powder is sintered, there is an advantage that the distribution of the crystal grain size of the sintered body is likely to be uniform.

  The method for granulating the raw material powder of the piezoelectric material is not particularly limited, but the most preferable granulation method is the spray drying method from the viewpoint that the particle size of the granulated powder can be made more uniform.

  Examples of binders that can be used when granulating include PVA (polyvinyl alcohol), PVB (polyvinyl butyral), and acrylic resins. The amount of the binder added is preferably 1 to 10 parts by weight with respect to the raw material powder of the piezoelectric material, and more preferably 2 to 7 parts by weight from the viewpoint of increasing the density of the molded body.

  The method for sintering the molded body is not particularly limited.

  Examples of the sintering method include sintering with an electric furnace, sintering with a gas furnace, current heating method, microwave sintering method, millimeter wave sintering method, HIP (hot isostatic pressing) and the like. The electric furnace and gas sintering may be a continuous furnace or a batch furnace.

  The sintering temperature in the sintering method is not particularly limited, but is preferably a temperature at which each compound reacts and sufficiently grows. A preferable sintering temperature is 1100 ° C. or higher and 1400 ° C. or lower, and more preferably 1150 ° C. or higher and 1300 ° C. or lower. The piezoelectric material sintered in the above temperature range exhibits good insulation and piezoelectric constant. In order to stabilize the characteristics of the piezoelectric material obtained by the sintering process in a reproducible manner, the sintering process is performed for 1 to 48 hours, more preferably 2 to 24 hours, with the sintering temperature kept constant within the above range. It is good to do. In addition, a sintering method such as a two-stage sintering method may be used, but a method without a rapid temperature change is preferable in consideration of productivity.

  The piezoelectric material obtained by the sintering process is polished into a desired shape according to the application. After the polishing process, heat treatment is preferably performed at a temperature equal to or higher than the Curie temperature. When mechanically polished, residual stress is generated inside the piezoelectric material. However, by performing heat treatment at a temperature equal to or higher than the Curie temperature, the residual stress is relaxed, and the piezoelectric characteristics of the piezoelectric material are further improved. Although the specific time of heat processing is not specifically limited, For example, the heat processing which hold | maintains the temperature of 300 to 500 degreeC for 1 to 24 hours is preferable.

  The average particle size of the crystals constituting the piezoelectric material of the present invention is preferably 0.2 μm or more and 50 μm or less from the viewpoint of achieving both piezoelectricity and processing strength. By setting the average particle size within the above range, it is possible to obtain mechanical strength during cutting and polishing while ensuring sufficient piezoelectricity. A more preferable range of the average particle diameter is 0.3 μm or more and 20 μm or less. In this specification, the average particle diameter means an average equivalent circle diameter. The equivalent circle diameter represents a “projected area equivalent circle diameter” generally referred to in a microscope observation method, and represents the diameter of a perfect circle having the same area as the projected area of crystal grains.

  Although the present invention relates to a piezoelectric material, any form such as powder, single crystal, film, slurry, etc. other than ceramics may be used.

  When the piezoelectric material of the present invention is used as a film formed on a substrate, the thickness of the piezoelectric material is desirably 200 nm or more and 10 μm or less, more preferably 300 nm or more and 3 μm or less. This is because a sufficient electromechanical conversion function as a piezoelectric element can be obtained by setting the film thickness of the piezoelectric material to 200 nm to 10 μm.

  The method for laminating the film is not particularly limited. For example, chemical solution deposition method (CSD method), sol-gel method, metal organic chemical vapor deposition method (MOCVD method), sputtering method, pulse laser deposition method (PLD method), hydrothermal synthesis method, aerosol deposition method (AD Law). Among these, the most preferable lamination method is a chemical solution deposition method or a sputtering method. The chemical solution deposition method or sputtering method can easily increase the film formation area. The substrate used for the piezoelectric material of the present invention is preferably a single crystal substrate cut and polished on the (001) plane, the (110) plane, or the (111) plane. By using a single crystal substrate cut and polished at a specific crystal plane, the piezoelectric material film provided on the substrate surface can be strongly oriented in the same direction.

(Piezoelectric element)
Next, the piezoelectric element of the present invention will be described.

  FIG. 1 is a schematic view showing an embodiment of the configuration of the piezoelectric element of the present invention. The piezoelectric element according to the present invention is a piezoelectric element having at least a first electrode 1, a piezoelectric material part 2 and a second electrode 3, and the piezoelectric material constituting the piezoelectric material part 2 is the piezoelectric material of the present invention. It is characterized by being.

  The piezoelectric material according to the present invention can be evaluated for its piezoelectric characteristics by forming a piezoelectric element having at least a first electrode and a second electrode. The first electrode and the second electrode are made of a conductive layer having a thickness of about 5 nm to 10 μm. The material is not particularly limited as long as it is usually used for piezoelectric elements. Examples thereof include metals such as Ti, Pt, Ta, Ir, Sr, In, Sn, Au, Al, Fe, Cr, Ni, Pd, Ag, and Cu, and compounds thereof.

  Said 1st electrode and 2nd electrode may consist of 1 type of these, or may laminate | stack these 2 types or more. Further, the first electrode and the second electrode may be made of different materials.

  The manufacturing method of the first electrode and the second electrode is not limited, and may be formed by baking a metal paste, or may be formed by sputtering, vapor deposition, or the like. Further, both the first electrode and the second electrode may be patterned into a desired shape and used.

(polarization)
The piezoelectric element is more preferably one having polarization axes aligned in a certain direction. When the polarization axes are aligned in a certain direction, the piezoelectric constant of the piezoelectric element increases.

  The polarization method of the piezoelectric element is not particularly limited. The polarization treatment may be performed in the air or in silicone oil. The temperature for polarization is preferably 60 ° C. to 150 ° C., but the optimum conditions differ somewhat depending on the composition of the piezoelectric material constituting the element. The electric field applied for the polarization treatment is preferably 800 V / mm to 3.0 kV / mm.

(PE hysteresis measurement)
Since the piezoelectric material layer of the piezoelectric element of the present invention has ferroelectric characteristics, it has polarization-electric field hysteresis characteristics. The polarization-electric field hysteresis characteristic means having a hysteresis effect in the relationship between the AC electric field applied to the ferroelectric and the amount of polarization generated by the ferroelectric. Due to this hysteresis effect, the piezoelectric material layer has positive or negative polarization even when the external electric field is zero, and this polarization value is referred to as residual polarization ± Pr. Similarly, the electric field in which the polarization amount becomes 0 is also divided into two, and the magnitude of these electric fields is called coercive electric field ± Ec.

  The polarization-electric field hysteresis characteristic is generally obtained by converting from the charge amount measured while applying a triangular wave voltage to a pair of opposing electrodes of the piezoelectric element, and is a commercially available device (eg, Toyo Technica FCE). Can be measured.

(Laminated piezoelectric element)
Next, a laminated piezoelectric element that is an embodiment of the piezoelectric element will be described.

  The laminated piezoelectric element according to the present invention includes the piezoelectric element including at least one internal electrode in the piezoelectric material portion, wherein the piezoelectric material layer made of the piezoelectric material and the layered at least one internal electrode are alternately arranged. It has the laminated structure laminated | stacked, It is characterized by the above-mentioned.

  FIG. 2 is a schematic cross-sectional view showing an embodiment of the configuration of the multilayer piezoelectric element of the present invention. The laminated piezoelectric element according to the present invention is composed of piezoelectric material layers 54 and 504 and electrode layers including internal electrodes 55 and 505, and these laminated piezoelectric elements are alternately laminated. The layers 54 and 504 are made of the above piezoelectric material. The electrode layer may include external electrodes such as the first electrodes 51 and 501 and the second electrodes 53 and 503 in addition to the internal electrodes 55 and 505.

  FIG. 2A shows a laminate of the present invention in which two piezoelectric material layers 54 and one internal electrode 55 are alternately laminated, and the laminated structure is sandwiched between a first electrode 51 and a second electrode 53. The structure of a piezoelectric element is shown. The number of piezoelectric material layers and internal electrodes may be increased as shown in FIG. 2B, and the number of layers is not limited. In the laminated piezoelectric element of FIG. 2B, nine piezoelectric material layers 504 and eight internal electrodes 505 (505a or 505b) are alternately laminated. The stacked structure has a structure in which a piezoelectric material layer is sandwiched between a first electrode 501 and a second electrode 503, and includes an external electrode 506a and an external electrode 506b for short-circuiting alternately formed internal electrodes.

  The size and shape of the internal electrodes 55 and 505 and the external electrodes 506a and 506b, the first electrodes 51 and 501 and the second electrodes 53 and 503 are not necessarily the same as those of the piezoelectric material layers 54 and 504. It may be divided.

  The internal electrodes 55 and 505, the external electrodes 506a and 506b, the first electrodes 51 and 501 and the second electrodes 53 and 503 are each made of a conductive layer having a thickness of about 5 nm to 10 μm. The material is not particularly limited as long as it is usually used for piezoelectric elements. Examples thereof include metals such as Ti, Pt, Ta, Ir, Sr, In, Sn, Au, Al, Fe, Cr, Ni, Pd, Ag, and Cu, and compounds thereof. The internal electrodes 55 and 505 and the external electrodes 506a and 506b may be made of one of them, a mixture of two or more kinds or an alloy, or a laminate of two or more of them. It may be a thing. The plurality of electrodes may be made of different materials.

  In the multilayer piezoelectric element using the piezoelectric material of the present invention, the internal electrodes 55 and 505 contain Ag and Pd, and the weight ratio M1 / M2 between the Ag content weight M1 and the Pd content weight M2 is 1. It is preferable that 5 ≦ M1 / M2 ≦ 9.0. If the weight ratio M1 / M2 is less than 1.5, the heat resistance of the internal electrode is high, but it is not desirable because the electrode cost increases due to an increase in the Pd component. On the other hand, when the weight ratio M1 / M2 is greater than 9.0, the internal electrode is formed in an island shape due to insufficient heat resistance temperature of the internal electrode, which is not desirable. From the viewpoint of heat resistance and cost, 2.0 ≦ M1 / M2 ≦ 5.0 is more preferable.

  From the viewpoint that the electrode material is inexpensive, the internal electrodes 55 and 505 preferably contain at least one of Ni and Cu. When at least one of Ni and Cu is used for the internal electrodes 55 and 505, the multilayer piezoelectric element of the present invention is preferably fired in a reducing atmosphere.

  As shown in FIG. 2B, a plurality of electrodes including the internal electrode 505 may be short-circuited with each other for the purpose of aligning the phases of the drive voltages. For example, the internal electrode 505a and the first electrode 501 may be short-circuited by the external electrode 506a. The internal electrode 505b and the second electrode 503 may be short-circuited by the external electrode 506b. The internal electrodes 505a and the internal electrodes 505b may be alternately arranged. Moreover, the form of the short circuit between electrodes is not limited. An electrode or wiring for short-circuiting may be provided on the side surface of the laminated piezoelectric element, or a through-hole penetrating the piezoelectric material layer 504 may be provided, and a conductive material may be provided inside to short-circuit the electrodes.

(Manufacturing method of laminated piezoelectric element)
The manufacturing method of the multilayer piezoelectric element according to the present invention is not particularly limited, but the manufacturing method thereof will be exemplified below. First, a step (A) of obtaining a slurry by dispersing a metal compound powder containing at least Mn, Na, Nb, Ba, and Ti, and a step (B) of obtaining a molded body by placing the slurry on a substrate Execute. Thereafter, a step (C) of forming an electrode on the molded body and a step (D) of sintering the molded body on which the electrode is formed to obtain a laminated piezoelectric element are executed.

The metal oxide that can be used in the step (A) is as exemplified as the raw material powder. Particularly desirable raw material powder combinations include sodium niobate (NaNbO ₃ ) calcined powder, barium titanate (BaTiO ₃ ) calcined powder, Ba—Nb composite calcined powder calcined by mixing barium carbonate and niobium oxide. And manganese oxide powder (for example, Mn ₃ O ₄ , MnO ₂ ), zirconate compounds (for example, calcium zirconate (CaZrO ₃ ), barium zirconate (BaZrO ₃ )). With this combination of raw material powders, crystallization proceeds at a relatively low temperature, for example, 1300 ° C. or lower, and the effect of the present invention of a high Curie temperature is easily obtained. More preferably, the metal oxide powder is calcined at a maximum temperature of 800 ° C. or higher and 1000 ° C. or lower and then slurried.

  An example of a method for preparing the slurry in the step (A) will be described. A solvent having a weight 1.6 to 1.7 times that of the metal compound powder is added and mixed. As the solvent, for example, toluene, ethanol, a mixed solvent of toluene and ethanol, n-butyl acetate, or water can be used. After mixing for 24 hours in a ball mill, a small amount of binder and plasticizer are added.

  Examples of the binder include PVA (polyvinyl alcohol), PVB (polyvinyl butyral), and acrylic resins. Examples of the plasticizer include dioctyl sebacate, dioctyl phthalate, and dibutyl phthalate. When dibutyl phthalate is used as the plasticizer, weigh the same weight as the binder. Then, the ball mill is performed again overnight. The amount of the solvent and binder is adjusted so that the viscosity of the slurry is 300 to 500 mPa · s.

  The molded body in the step (B) is a sheet-shaped mixture of the metal compound powder, binder and plasticizer. As a method of obtaining the molded body in the step (B), for example, there is sheet molding. For the sheet molding, for example, a doctor blade method can be used. The doctor blade method is a method of forming a sheet-shaped molded body by applying the slurry onto the substrate using a doctor blade and drying the slurry.

  As the substrate, for example, a pet film can be used. For example, fluorine coating on the surface on which the pet film slurry is placed is desirable because it facilitates peeling of the molded product. Drying may be natural drying or hot air drying. The thickness of the molded body is not particularly limited and can be adjusted according to the thickness of the laminated piezoelectric element. The thickness of the molded body can be increased by increasing the viscosity of the slurry, for example.

  The manufacturing method of the electrode in the step (C), that is, the internal electrode 505 and the external electrodes 506a and 506b is not limited, and may be formed by baking a metal paste, or formed by sputtering, vapor deposition, printing, or the like. Good. In order to reduce the driving voltage, the layer thickness and pitch interval of the piezoelectric material layer 504 may be reduced. In that case, after forming the laminated body including the precursor of the piezoelectric material layer 504 and the internal electrodes 505a and 505b, the process of simultaneously firing the laminated body is selected. In that case, a material for the internal electrode that does not cause a shape change or deterioration of conductivity due to a temperature necessary for sintering the piezoelectric material layer 504 is required. A metal or an alloy thereof having a lower melting point and lower cost than Pt such as Ag, Pd, Au, Cu and Ni can be used for the internal electrodes 505a and 505b and the external electrodes 506a and 506b. However, the external electrodes 506a and 506b may be provided after the laminate is fired. In that case, in addition to Ag, Pd, Cu, and Ni, Al or a carbon-based electrode material can be used.

  A screen printing method is desirable as a method for forming the electrodes. The screen printing method is a method of applying a metal paste using a spatula after a screen plate is placed on a molded body placed on a substrate. A screen mesh is formed at least partially on the screen plate. Therefore, the metal paste in the portion where the screen mesh is formed is applied onto the molded body. The screen mesh in the screen plate is preferably formed with a pattern. By transferring the pattern to the molded body using a metal paste, the electrode can be patterned on the molded body.

  After forming the electrode in the step (C), after peeling from the base material, one or a plurality of the compacts are stacked and pressure-bonded. Examples of the pressure bonding method include uniaxial pressing, cold isostatic pressing, and warm isostatic pressing. Warm isostatic pressing is desirable because it can apply pressure isotropically and uniformly. Heating to near the glass transition temperature of the binder during pressure bonding is desirable because it enables better pressure bonding. A plurality of the compacts can be stacked and pressure-bonded until a desired thickness is reached. For example, after 5 to 100 layers of the molded body are stacked, the molded body can be stacked by thermocompression bonding at a pressure of 10 to 60 MPa at 50 to 80 ° C. in a stacking direction from 10 seconds to 10 minutes. . Moreover, by attaching alignment marks to the electrodes, a plurality of molded bodies can be aligned and stacked with high accuracy. Further, it is possible to stack accurately by providing positioning through holes in the molded body.

  Although the sintering temperature of the molded body in the step (D) is not particularly limited, it is preferably a temperature at which each compound reacts and sufficiently grows crystals. A preferable sintering temperature is 1100 ° C. or higher and 1400 ° C. or lower, more preferably 1150 ° C. or higher and 1300 ° C. or lower, from the viewpoint that the particle size of the ceramic is in the range of 0.2 μm to 50 μm. A laminated piezoelectric element sintered in the above temperature range exhibits good piezoelectric performance.

However, when a material containing Ni as a main component is used for the electrode in the step (C), the step (D) is preferably performed in a furnace capable of atmospheric firing. After burning and removing the binder at a temperature of 200 ° C. to 600 ° C. in the air atmosphere, the binder is changed to a reducing atmosphere and sintered at a temperature of 1200 ° C. to 1550 ° C. Here, the reducing atmosphere refers to an atmosphere mainly composed of a mixed gas of hydrogen (H ₂ ) and nitrogen (N ₂ ). The volume ratio of hydrogen and nitrogen is preferably in the range of H ₂ : N ₂ = 1: 99 to H ₂ : N ₂ = 10: 90. The mixed gas may contain oxygen. The oxygen concentration is 10 ⁻¹² Pa or more and 10 ⁻⁴ Pa or less. More preferably, it is 10 ⁻⁸ Pa or more and 10 ⁻⁵ Pa or less. The oxygen concentration can be measured with a zirconia oxygen analyzer. By using the Ni electrode, the multilayer piezoelectric element of the present invention can be manufactured at low cost. After firing in a reducing atmosphere, the temperature is preferably lowered to 600 ° C., and the atmosphere is preferably changed to an air atmosphere (oxidizing atmosphere) to perform an oxidation treatment. After taking out from the firing furnace, a conductive paste is applied to the side surface of the element body where the end of the internal electrode is exposed and dried to form the external electrode.

(Electronics)
An electronic apparatus according to the present invention includes the piezoelectric element according to the present invention.

(Example of electronic equipment 1: liquid ejection head, liquid ejection device)
FIGS. 3A and 3B are schematic diagrams schematically showing the configuration of a liquid discharge head including the piezoelectric element of the present invention and a liquid discharge apparatus using the liquid discharge head as an example of the electronic apparatus of the present invention. It is. The liquid discharge head includes at least a liquid chamber provided with a vibrating portion in which the piezoelectric element or the multilayer piezoelectric element is disposed, and a discharge port communicating with the liquid chamber. The liquid ejecting apparatus includes a receiving part mounting portion and the liquid ejecting head. However, the shape and arrangement of each member are not limited to the examples shown in FIGS.

  As shown in FIG. 3A, a liquid discharge head which is an electronic apparatus of the present invention has the piezoelectric element 101 of the present invention. The piezoelectric element 101 includes at least a first electrode 1011, a piezoelectric material 1012, and a second electrode 1013. The piezoelectric material 1012 and the second electrode 1013 may be patterned for the purpose of increasing the ejection force of the liquid ejection head.

  The liquid ejection head includes an ejection port 105, an individual liquid chamber 103, a communication hole 106 that connects the individual liquid chamber 103 and the ejection port 105, a liquid chamber partition wall 104, a common liquid chamber 107, a vibration plate 102, and a piezoelectric element 101. In general, the piezoelectric material 1012 has a shape along the shape of the individual liquid chamber 103.

  When an electric signal is input to and driven by a liquid discharge head which is an example of the electronic apparatus of the present invention, the vibration plate 102 vibrates up and down due to the deformation of the piezoelectric element 101, and pressure is applied to the liquid stored in the individual liquid chamber 103. . As a result, liquid is discharged from the discharge port 105. The liquid discharge head can be used for incorporation into a printer that performs printing on various media and for manufacturing an electronic device.

  Next, a liquid discharge apparatus using the liquid discharge head will be described.

  This liquid ejection apparatus is also an example of the electronic apparatus of the present invention. FIG. 3B illustrates a liquid discharge apparatus as an ink jet recording apparatus.

  In the liquid ejection device in FIG. 3B, each mechanism is incorporated in the exterior portion 896. The automatic feeding unit 897 has a function of automatically feeding a recording sheet as a transfer target into the apparatus main body. The recording sheet sent from the automatic feeding unit 897 is guided to a predetermined recording position (no figure number) by the conveyance unit 899, and after the recording operation, is again guided from the recording position to the discharge unit 898 by the conveyance unit 899. A conveyance unit 899 is a placement unit for the transfer target. In addition, the liquid ejecting apparatus includes a recording unit 891 that performs recording on the recording paper conveyed to the recording position, and a recovery unit 890 that performs recovery processing on the recording unit 891. The recording unit 891 includes a carriage 892 that houses the liquid discharge head and reciprocates on the rail.

  In such a liquid discharge apparatus, the carriage 892 moves the liquid discharge head in accordance with an instruction from an external computer, and ink is discharged from the discharge port 105 of the liquid discharge head in response to voltage application to the piezoelectric element of the present invention. Thus, printing is performed.

  Although the above example is illustrated as a printer, the liquid discharge apparatus of the present invention is used as a printing apparatus such as an inkjet recording apparatus such as a facsimile, a multi-function machine, and a copying machine, as well as an industrial liquid discharge apparatus and a drawing apparatus for an object. can do. In addition, the user can select a desired transfer object according to the application.

(Example of electronic equipment 2: vibration wave motor, optical equipment)
4A to 4E are schematic views schematically showing a configuration of a vibration wave motor including the piezoelectric element of the present invention and an optical apparatus using the vibration wave motor as an example of the electronic apparatus of the present invention. It is. The vibration wave motor includes at least a vibrating body provided with the piezoelectric element or the laminated piezoelectric element, and a moving body in contact with the vibrating body. The optical apparatus includes the vibration wave motor in the drive unit. However, the shape and arrangement of each member are not limited to the examples shown in FIGS.

  A vibration wave motor in which the piezoelectric element of the present invention is a single plate is shown in FIG. The vibration wave motor is provided integrally with the vibrating body 201, a moving body 202 (also referred to as a rotor) that is in contact with the sliding surface of the vibrating body 201 with a pressure spring (not shown), and a moving body 202. An output shaft 203 is provided. The vibrating body 201 is composed of a metal elastic ring 2011, a piezoelectric element 2012 of the present invention, and an organic adhesive 2013 (epoxy-based, cyanoacrylate-based, etc.) that bonds the piezoelectric element 2012 to the elastic ring 2011.

  When a two-phase alternating voltage having a phase that is an odd multiple of π / 2 is applied to the piezoelectric element, a bending traveling wave is generated in the vibrating body 201 and each point on the sliding surface of the vibrating body 201 performs an elliptical motion. The rotor 202 receives frictional force from the vibrating body 201 and rotates in a direction opposite to the bending traveling wave. A driven body (not shown) is joined to the output shaft 203 and is driven by the rotational force of the rotor 202.

  Next, FIG. 4B illustrates a vibration wave motor including a piezoelectric element (laminated piezoelectric element) having a laminated structure. The vibrating body 204 includes a laminated piezoelectric element 2042 sandwiched between cylindrical metal elastic bodies 2041. The laminated piezoelectric element 2042 is the above-described laminated type element, and has a first electrode and a second electrode on the outer surface of the laminate, and an internal electrode on the inner surface of the laminate. The metal elastic body 2041 sandwiches and fixes the laminated piezoelectric element 2042 with a bolt to constitute the vibrating body 204.

  By applying alternating voltages having different phases to the laminated piezoelectric element 2042, the vibrating body 204 excites two vibrations orthogonal to each other. These two vibrations are combined to form a circular vibration for driving the tip of the vibrating body 204. A constricted circumferential groove is formed in the upper part of the vibrating body 204 to increase the vibration displacement for driving.

  The moving body 205 (also referred to as a rotor) is brought into pressure contact with the vibrating body 204 by a pressurizing spring 206 to obtain a frictional force for driving. The moving body 205 is rotatably supported by a bearing.

  Next, an optical apparatus using the vibration wave motor will be described.

  This optical apparatus is also an example of the electronic apparatus of the present invention. FIGS. 4C, 4D, and 4E illustrate an optical apparatus as an interchangeable lens barrel of a single-lens reflex camera.

  A fixed cylinder 712, a rectilinear guide cylinder 713, and a front group lens barrel 714 are fixed to a detachable mount 711 with the camera. These are fixing members for the interchangeable lens barrel.

  The rectilinear guide tube 713 is formed with a rectilinear guide groove 713a for the focus lens 702 in the optical axis direction. Cam rollers 717a and 717b projecting radially outward are fixed to the rear group barrel 716 holding the focus lens 702 by shaft screws 718, and the cam rollers 717a are fitted in the rectilinear guide grooves 713a.

  A cam ring 715 is rotatably fitted on the inner periphery of the rectilinear guide tube 713. The linear movement guide cylinder 713 and the cam ring 715 are restricted from moving relative to each other in the optical axis direction by the roller 719 fixed to the cam ring 715 being fitted in the circumferential groove 713b of the linear movement guide cylinder 713. The cam ring 715 is formed with a cam groove 715a for the focus lens 702, and the cam roller 717b is fitted into the cam groove 715a at the same time.

  A rotation transmission ring 720 that is held by a ball race 727 so as to be rotatable at a fixed position with respect to the fixed cylinder 712 is disposed on the outer peripheral side of the fixed cylinder 712. In the rotation transmission ring 720, a roller 722 is rotatably held on a shaft 720f extending radially from the rotation transmission ring 720, and the large diameter portion 722a of the roller 722 is in contact with the mount side end surface 724b of the manual focus ring 724. doing. The small diameter portion 722 b of the roller 722 is in contact with the joining member 729. Six rollers 722 are arranged on the outer periphery of the rotation transmission ring 720 at equal intervals, and each roller is configured in the above relationship.

  A low friction sheet (washer member) 733 is disposed on the inner diameter portion of the manual focus ring 724, and this low friction sheet is sandwiched between the mount side end surface 712 a of the fixed cylinder 712 and the front end surface 724 a of the manual focus ring 724. Yes. Further, the outer diameter surface of the low friction sheet 733 has a ring shape and is fitted with the inner diameter 724c of the manual focus ring 724, and the inner diameter 724c of the manual focus ring 724 is fitted with the outer diameter portion 712b of the fixed cylinder 712. Match. The low friction sheet 733 serves to reduce friction in the rotating ring mechanism in which the manual focus ring 724 rotates relative to the fixed cylinder 712 around the optical axis.

  The large diameter portion 722a of the roller 722 and the mount side end surface 724b of the manual focus ring are in contact with each other in a state where pressure is applied by the force of the wave washer 726 pressing the vibration wave motor 725 forward of the lens. . Similarly, the wave washer 726 is in contact with the small diameter portion 722b of the roller 722 and the joining member 729 in a state where an appropriate pressure is applied by the force of pressing the vibration wave motor 725 forward of the lens. The wave washer 726 is restricted from moving in the mounting direction by a washer 732 that is bayonet-coupled to the fixed cylinder 712. The spring force (biasing force) generated by the wave washer 726 is transmitted to the vibration wave motor 725 and further to the roller 722, and the manual focus ring 724 also serves as a pressing force against the mount side end surface 712a of the fixed barrel 712. That is, the manual focus ring 724 is incorporated in a state of being pressed against the mount side end surface 712 a of the fixed cylinder 712 via the low friction sheet 733.

  Therefore, when the ultrasonic motor 725 is rotationally driven with respect to the fixed cylinder 712 by a control unit (not shown), the joining member 729 is in frictional contact with the small diameter portion 722b of the roller 722, so that the roller 722 is centered on the shaft 720f. Rotate around. When the roller 722 rotates around the axis 720f, as a result, the rotation transmission ring 720 rotates around the optical axis.

  Two focus keys 728 are attached to the rotation transmission ring 720 at positions facing each other, and the focus key 728 is fitted with a notch 715 b provided at the tip of the cam ring 715. Accordingly, when the rotation transmission ring 720 rotates around the optical axis, the rotational force is transmitted to the cam ring 715 via the focus key 728. When the cam ring is rotated around the optical axis, the rear group barrel 716 whose rotation is restricted by the cam roller 717a and the straight guide groove 713a advances and retreats along the cam groove 715a of the cam ring 715 by the cam roller 717b. As a result, the focus lens 702 is driven and a focus operation is performed.

  In the above example, an interchangeable lens barrel of a single-lens reflex camera is described as an optical device using the vibration wave motor, but a vibration wave motor is used in the drive unit regardless of the type of camera, such as a compact camera or an electronic still camera. The vibration wave motor can be applied to an optical apparatus having the above.

(Example 3 of electronic equipment: vibration device, imaging device)
FIGS. 5A to 5D are schematic diagrams schematically showing the configuration of a vibration device including the piezoelectric element of the present invention and an imaging device using the vibration device as an example of the electronic apparatus of the present invention. . The vibration device shown in FIG. 5 is a dust removal device that has at least a vibration body in which the piezoelectric element of the present invention is arranged on a vibration plate and has a function of removing dust attached to the surface of the vibration plate. The imaging device is an imaging device having at least the dust removing device and an imaging element unit, and the diaphragm of the dust removing device is provided on the light receiving surface side of the imaging element unit.

  However, the shape and arrangement of each member are not limited to the examples shown in FIGS.

  FIG. 5A and FIG. 5B are schematic views showing one embodiment of an electronic apparatus as a dust removing device. The dust removing device 310 includes a plate-like piezoelectric element 330 and a diaphragm 320. The piezoelectric element 330 may be the stacked piezoelectric element of the present invention. Although the material of the diaphragm 320 is not limited, when the dust removing device 310 is used for an optical device, a light-transmitting material or a light-reflecting material can be used as the diaphragm 320. The part is the target of dust removal.

  The piezoelectric element 330 includes a piezoelectric material 331, a first electrode 332, and a second electrode 333, and the first electrode 332 and the second electrode 333 are disposed to face the plate surface of the piezoelectric material 331. . In the case of a laminated piezoelectric element, the piezoelectric material 331 has an alternating structure of piezoelectric material layers and internal electrodes, and the internal electrodes are alternately short-circuited with the first electrode 332 or the second electrode 333, whereby a layer of piezoelectric material is obtained. A drive waveform having a different phase can be provided for each. In FIG. 5A, the first electrode 332 wraps around the side where the second electrode 333 is present.

  When an alternating voltage is applied to the piezoelectric element 330 from the outside, a stress is generated between the piezoelectric element 330 and the diaphragm 320, and an out-of-plane vibration is generated in the diaphragm. The dust removing device 310 is a device that removes foreign matters such as dust attached to the surface of the diaphragm 320 by the out-of-plane vibration of the diaphragm 320. Out-of-plane vibration is elastic vibration that displaces the diaphragm in the optical axis direction, that is, in the thickness direction of the diaphragm.

  Next, an imaging device using the dust removing device will be described. This imaging apparatus is also an example of the electronic apparatus of the present invention. FIGS. 5C and 5D illustrate an imaging apparatus as a digital single-lens reflex camera.

  FIG. 5C is a front perspective view of the camera body 601 viewed from the subject side, and shows a state in which the taking lens unit is removed. FIG. 5D is an exploded perspective view showing a schematic configuration inside the camera for explaining the dust removing device and the peripheral structure of the imaging unit 400.

  A mirror main body (quick return mirror) 606 is provided in the mirror box 605 in the camera body 601 shown in FIG. ing. The main mirror 606 is in a state of being held at an angle of 45 ° with respect to the photographing optical axis in order to guide the photographing light beam in the direction of the penta roof mirror (not shown) and in order to guide the imaging light beam in the direction of the imaging element (not shown). It can be in a state of being held at a position retracted from the photographing light flux.

  In FIG. 5D, a mirror box 605 and a shutter unit 200 are arranged in order from the subject side on the subject side of the main body chassis 300 which is a skeleton of the camera body. An imaging unit 400 is disposed on the photographer side of the main body chassis 300. The imaging unit 400 includes a diaphragm of a dust removing device and an imaging element unit. Further, the vibration plate of the dust removing device is sequentially provided on the same axis as the light receiving surface of the image sensor unit. The imaging unit 400 is installed on a mounting surface of a mount portion 602 (FIG. 5C) serving as a reference to which the imaging lens unit is attached, the imaging surface of the imaging element unit is spaced a predetermined distance from the imaging lens unit, and It is adjusted to be parallel.

  Here, a digital single-lens reflex camera has been described as an example of the imaging apparatus, but a photographing lens unit exchangeable camera such as a mirrorless digital single-lens camera that does not include the mirror box 605 may be used. In addition, various types of imaging devices such as a video camera with interchangeable photographic lens unit, copying machines, facsimiles, scanners, etc. or electronic / electronic devices equipped with imaging devices that require removal of dust adhering to the surface of optical components. It can also be applied to.

  Up to this point, a liquid discharge head, a liquid discharge device, a vibration wave motor, an optical device, a vibration device, and an imaging device have been described as examples of the electronic device of the present invention, but the types of electronic devices are not limited to these. Electronic devices that detect electrical signals and extract energy due to the positive piezoelectric effect by extracting power from the piezoelectric element, and electronic devices that use displacement due to the reverse piezoelectric effect by inputting power to the piezoelectric element In general, the piezoelectric element of the present invention is applicable. For example, a piezoelectric acoustic component, a voice reproducing device, a voice recording device, a mobile phone, an information terminal, and the like having the piezoelectric acoustic component are also included in the electronic device of the present invention.

  The piezoelectric material of the present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples.

  Tables 1 and 2 show the compositions and firing temperatures of the sintered bodies of Examples 11 to 13, 21 to 23, 31 to 33 and Comparative Examples 11, 21, and 31 of the present invention. In the table, t, z, β, α, m, and γ are Ti abundance, Zr abundance, Ba abundance, Na abundance, Mn abundance, where Nb abundance is 1, respectively. , Represents the abundance of Ca.

  The composition of the sintered body was evaluated by ICP (Inductively Coupled Plasma Atomic Emission Spectroscopy), and there was a measurement distribution of 5 to 10%, including the repetition error of sample synthesis and the measurement error of the apparatus. For example, regarding the composition parameters of the sample groups in Examples 11 to 33, the t value is distributed in the range of 0.10 to 0.155, and the z value is distributed in the range of 0.010 to 0.037. Β values are distributed in the range of 0.10 to 0.17, α values are distributed in the range of 0.95 to 1.03, and m value is 0.0006 to 0.0025. It was distributed in range. The compositions shown in Tables 1 and 2 are average values of these.

  In Examples 11 to 13 and Comparative Example 1, the general formula (1) Na (α) Ba (β) Nb (1) Ti (t) -Zr (z) -Mn (m) -Ca (γ) The raw materials were weighed so as to be t, z, β, α, m and γ.

  Examples 21 to 23, 31 to 33 and Comparative Examples 21 and 31 are represented by the formula (2) Na (α) Ba (β) Nb (1) Ti (t) -Zr (z) -Mn (m). The raw materials were weighed so as to be t, z, β, α, and m. However, Examples 21 to 23, 31 to 33 and Comparative Examples 21 and 31 were prepared in such a manner that 0.011 Zn was added to the elements shown in Table 2 when the abundance of Nb was 1.

  The raw material powders of the examples were mixed by ball milling for 12 hours.

Examples of the raw materials of Examples 11 to 13 and Comparative Example 11 include sodium niobate (NaNbO ₃ ) with a purity of 99% or more, barium titanate (BaTiO ₃ ) with a purity of 99% or more, calcium zirconate (CaZrO with a purity of 99% or more) ₃ ) Manganese oxide (Mn ₃ O ₄ ) powder having a purity of 99.9% was used.

The raw materials of Examples 21 to 23, 31 to 33, and Comparative Examples 21 and 31 were sodium niobate (NaNbO ₃ ) having a purity of 99% or more, barium titanate (BaTiO ₃ ) having a purity of 99% or more, and a purity of 99% or more. Barium zirconate (BaZrO ₃ ), manganese oxide (MnO ₂ ) having a purity of 99.9%, and zinc oxide (ZnO) having a purity of 99% or more were used.

  The mixed powder was calcined in the atmosphere at 900 ° C. to 1100 ° C. for 2 to 5 hours. The calcined powder was pulverized and granulated by adding 3% by weight of PVB binder to the weight of the calcined powder. The granulated powder was filled in a mold and compressed at a pressure of 200 MPa to produce a molded body having a diameter of 17 mm and a thickness of about 1 mm. The obtained compact was fired in air at 1100 ° C. to 1280 ° C. for 2 to 6 hours to obtain a sintered body. However, even if this calcining step is omitted, a piezoelectric material having the effects of the present invention can be obtained.

  When the density of the sintered body was measured by the Archimedes method and the relative density was calculated, the relative density of all the sintered bodies was 94% or more.

  The relative density is a ratio of the actually measured density to the theoretical density calculated from the lattice constant of the piezoelectric material and the atomic weight of the constituent elements of the piezoelectric material. The lattice constant can be measured by, for example, X-ray diffraction analysis. The density can be measured by, for example, a known Archimedes method.

  The sintered body was polished so as to have a thickness of about 0.5 mm. X-ray diffraction was performed using the polished sintered body or powder obtained by pulverizing the polished sintered body, and the constituent phases and the lattice constants were evaluated. It was confirmed by X-ray diffraction that the sample was almost a single phase of perovskite structure.

  The particle size in the sintered body was evaluated by observing with an optical microscope or an electron microscope.

  When the particle size of the sintered body was observed with an electron microscope, the average particle size was in the range of 2 to 70 μm.

  In addition, 30 nm of titanium was formed as an adhesion layer between the electrode and the ceramic. This ceramic with electrodes was cut to produce a 10 mm × 2.5 mm × 0.5 mmt strip-shaped piezoelectric element.

  A semiconductor parameter analyzer was used to evaluate the resistivity. A DC voltage of several tens to 100 volts was applied to the sample, and the resistance after 30 seconds from the start of voltage application was measured. The resistivity was calculated from the measured resistance and sample dimensions.

  The electric field-polarization hysteresis measurement was performed in order to determine the presence or absence of ferroelectricity in a practical electric field of the target element at room temperature. A material exhibiting ferroelectricity in a certain temperature region has piezoelectricity in the same temperature region and can be used as a memory material. Specifically, the amount of polarization when an AC electric field (triangular wave) was applied to the piezoelectric element of the present invention was measured. The frequency of the alternating electric field was 10 to 100 Hz. The maximum electric field strength was about ± 50 kV / cm.

  Prior to the evaluation of piezoelectric characteristics, polarization treatment was performed. Specifically, in an oil bath maintained at 110 to 150 ° C., a voltage of 1.5 to 5 kV / mm was applied to the sample for 30 minutes, and the sample was cooled to room temperature while the voltage was applied.

The piezoelectric constant (d ₃₁ ), mechanical quality factor (Qm), and dielectric loss tangent (tan δ) of the strip-shaped piezoelectric element were measured by a resonance anti-resonance method. The piezoelectric constant (d ₃₃ ) was evaluated by a d ₃₃ meter based on the Berlin coat method using the same sample. An impedance analyzer was used to measure the relative permittivity. The relative dielectric constant in this specification is a value at a measurement frequency of 1 kHz, and the magnitude of the applied AC electric field is 500 mV. The measurement was performed after the polarization treatment. When evaluating the temperature dependence of relative permittivity, measurement of relative permittivity starts from room temperature, changes in relative permittivity when the sample is cooled from room temperature to -100 ° C and then heated to 350 ° C. The Curie temperature and the sequential phase transition temperature were calculated from the maximum relative dielectric constant.

  Tables 2, 3 and 4 show the characteristics of representative samples.

(Piezoelectric materials and piezoelectric elements of Examples 11 to 13 and Comparative Example 11)
Examples 11 to 13 are samples in which z representing the amount of Zr with respect to Nb is 0.029 and m representing the amount of Mn is 0.0007 to 0.0011. As shown in Table 3 and FIG. 6A, | d ₃₃ / d ₃₁ | increased with the addition of Mn. Further, as shown in Table 5, an increase in Curie temperature was obtained. Further, as shown in Table 4 and FIG. 6B, in Examples 11 to 13, good results such as an increase in resistivity and a decrease in dielectric loss tangent were obtained as compared with Comparative Example 11 in which Mn was not added. On the other hand, if Mn is added in excess of 0.005 mol%, a perovskite metal oxide is not formed, the resistivity is remarkably lowered, and piezoelectric properties cannot be measured.

(Piezoelectric materials and piezoelectric elements of Examples 21 to 23 and Comparative Example 21)
Examples 21 to 23 are samples in which m representing the amount of Mn relative to Nb in the perovskite type metal oxide represented by the general formula (2) is 0.0023, and z representing the amount of Zr is 0.011 to 0.034. Is fired at 1150 ° C. The resistivity of the samples of Examples 21 to 23 was a high value as shown in Table 4, and the dielectric loss tangent (tan δ) was a low value of 0.02 or less as shown in Table 3. FIG. 7 is a diagram showing the relationship between the | d ₃₃ / d ₃₁ | value and the Zr amount in the piezoelectric elements of Examples 21 to 23, _{31 to 33} and Comparative Examples 21 and 31 of the present invention. An increase in the dielectric constant was observed with the addition of Zr. Further, in Comparative Examples 21 to 23 in which Zr was not added, in Examples 21 to 23, | d ₃₃ / d ₃₁ | increased with the addition of Zr. Further, as shown in Table 3, the mechanical quality factor (Qm) increased with the addition of Zr. On the other hand, the Curie temperature (Tc) decreases according to the amount of Zr added. If z representing the amount of Zr exceeds 0.04, the Curie temperature is remarkably lowered and the resistivity is also remarkably lowered, which is not preferable as a material used for the piezoelectric element.

(Piezoelectric materials and piezoelectric elements of Examples 31 to 33 and Comparative Example 31)
In Examples 31 to 33, in the piezoelectric material made of the perovskite metal oxide represented by the general formula (2), m representing the amount of Mn relative to Nb in the piezoelectric material is 0.0023, and z representing the amount of Zr is 0.00. Samples 011 to 0.034 were fired at 1100 ° C. The resistivity of the samples of Examples 31 to 33 was high as shown in Table 4, and the dielectric loss tangent (tan δ) was a low value of 0.02 or less. An increase in the dielectric constant was observed with the addition of Zr. Furthermore, | d ₃₃ / d ₃₁ | increased with the addition of Zr in Examples 31 to 33 as compared with Comparative Example 31 in which Zr was not added. Moreover, the mechanical quality factor (Qm) increased with the addition of Zr. On the other hand, the Curie temperature (Tc) decreases according to the amount of Zr added. When z representing the amount of Zr exceeds 0.04, the Curie temperature is remarkably lowered and the resistivity is also remarkably lowered, which is not preferable as a piezoelectric element material.

  The samples of Examples 31 to 33 were polished and subjected to X-ray diffraction measurement. As the amount of Zr was increased, the a-axis length was increased and the c / a ratio of the perovskite structure tended to decrease.

  The relative dielectric constant at room temperature is more preferably 1300 or less from the viewpoint of low power consumption.

(Hysteresis curves of the piezoelectric materials of Examples 21 to 23 and Comparative Example 21)
The electric field-polarization hysteresis measurement results of the piezoelectric materials of Examples 21 to 23 and Comparative Example 21 are shown in FIG. With the addition of Zr, the hysteresis curve decreased as the amount of Zr increased. That is, a decrease in the remanent polarization value (polarization value Pr when the applied electric field is zero) and a coercive electric field (applied electric field Ec when the sign of polarization is reversed), which are thought to be caused by reduced pinning of spontaneous polarization, are observed. It was.

(Example 41)
A laminated type piezoelectric element of the present invention was prepared in the following manner.

  A PVB binder was added to and mixed with the 900 ° C. calcined powder before spray-dry granulation in Example 12, and then a sheet was formed by a doctor blade method to obtain a green sheet having a thickness of 50 μm.

  A conductive paste for internal electrodes was printed on the green sheet. As the conductive paste, an Ag 70% -Pd 30% alloy (Ag / Pd = 2.33) paste was used. Nine green sheets coated with the conductive paste were laminated, and the laminate was fired at 1200 ° C. for 5 hours to obtain a sintered body. A pair of external electrodes (first electrode and second electrode) for alternately short-circuiting the internal electrodes are formed by Au sputtering after the sintered body is cut into a size of 10 mm × 2.5 mm and the side surfaces thereof are polished. Then, a laminated piezoelectric element as shown in FIG.

  When the cross section of the obtained laminated piezoelectric element was observed, internal electrodes and piezoelectric material layers made of Ag—Pd were alternately formed.

  The laminated piezoelectric element was subjected to polarization treatment. Specifically, the sample was heated to 150 ° C. in an oil bath, a voltage of 2 kV / mm was applied between the first electrode and the second electrode for 30 minutes, and the sample was cooled to room temperature while the voltage was applied.

  When the piezoelectric characteristics of the obtained multilayer piezoelectric element were evaluated, it had sufficient insulation, and the piezoelectric constant, Curie temperature, and dielectric loss tangent equivalent to those of the piezoelectric material of Example 12 could be obtained.

(Example 42)
Using the piezoelectric elements of Example 12 and Example 41, the liquid discharge head shown in FIG. Ink ejection following the input electrical signal was confirmed.

  A liquid discharge apparatus shown in FIG. 3B was manufactured using this liquid discharge head. Ink ejection following the input electrical signal was confirmed on the recording medium.

(Example 43)
Using the piezoelectric elements of Example 12 and Example 41, an ultrasonic motor shown in FIG. 4A or FIG. 4B was produced. The rotation of the motor according to the application of the AC voltage was confirmed.

  Using this ultrasonic motor, the optical apparatus shown in FIGS. 4C, 4D and 4E was produced. The autofocus operation according to the application of AC voltage was confirmed.

(Example 44)
Using the piezoelectric elements of Example 12 and Example 41, a dust removing device shown in FIGS. 5A and 5B was produced. When plastic beads were sprayed and an AC voltage was applied, a good dust removal rate was confirmed.

  Using this dust removing device, the imaging device shown in FIGS. 5C, 5D and 5E was manufactured. When this imaging device was energized, dust on the surface of the imaging unit was removed well, and an image free from dust defects was obtained.

  The piezoelectric material of the present invention exhibits good piezoelectricity even at a high ambient temperature. Moreover, since it does not contain lead, there is little burden on the environment. Therefore, the piezoelectric material of the present invention can be used without problems for devices that use a large amount of piezoelectric material, such as a liquid discharge head, a vibration wave motor, and a dust removing device.

DESCRIPTION OF SYMBOLS 1 1st electrode 2 Piezoelectric material part 3 2nd electrode 101 Piezoelectric element

Claims (10)

A piezoelectric material comprising Na, Ba, Nb, Ti, Zr, Mn and made of a perovskite oxide,
T indicating the molar ratio of Ti to Nb is 0.08 ≦ t ≦ 0.15,
Z indicating the molar ratio of Zr to Nb is 0.01 ≦ z ≦ 0.04,
Β indicating the molar ratio of Ba to Nb is 0.08 ≦ β ≦ 0.17,
Piezoelectric material wherein α indicating the molar ratio of Na to Nb is 0.95 ≦ α ≦ 1.03, and m indicating the molar ratio of Mn to Nb is 0.0005 ≦ m ≦ 0.0025 .   The piezoelectric material according to claim 1, wherein β is 0.08 ≦ β ≦ 0.15. The piezoelectric material further includes Ca,
3. The piezoelectric material according to claim 1, wherein γ indicating the molar ratio of Ca to Zr is 0.97 ≦ γ ≦ 1.03.   The piezoelectric material according to any one of claims 1 to 3, wherein a total of Pb component and K component contained in the piezoelectric material is less than 1000 ppm.   The piezoelectric material according to any one of claims 1 to 4, wherein a relative dielectric constant at room temperature is 1300 or less. The piezoelectric material according to any one of claims 1 to 5 piezoelectric constant _{d 33} is 200 pm / V or more. The piezoelectric material according to claim 1, wherein the piezoelectric constant | d ₃₃ / d ₃₁ | is 4.0 or more. A piezoelectric element having a piezoelectric material portion and an electrode,
A piezoelectric element, wherein the piezoelectric material constituting the piezoelectric material portion is the piezoelectric material according to any one of claims 1 to 7.   The piezoelectric element according to claim 8, wherein the piezoelectric material portions and the electrodes are alternately stacked.   An electronic device comprising the piezoelectric element according to claim 8.

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