JP2010030810A - Piezoelectric/electrostrictive ceramics sintered compact - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To find new indications or items which can cause the improvement of properties, to provide a method for correctly evaluating the same, and to provide a niobate alkali-type piezoelectric/electrostrictive ceramics sintered compact whose electric properties are improved based on the results therefrom. <P>SOLUTION: Disclosed is a niobate alkali-type piezoelectric/electrostrictive ceramics sintered compact in which a tetragonal perovskite-type oxide is the main crystal phase, and the skewness of the diffraction peaks in the (002) faces of the tetragonal crystals is 1 to 3.3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an alkaline niobate-based piezoelectric / electrostrictive ceramic sintered body used for actuators and sensors.

  Piezoelectric / electrostrictive actuators have the advantage that displacement can be precisely controlled on the order of submicrons. In particular, a piezoelectric / electrostrictive actuator using a piezoelectric / electrostrictive ceramic sintered body as a piezoelectric / electrostrictive body (piezoelectric / electrostrictive element) has an electromechanical conversion efficiency in addition to precisely controlling the displacement. It has the advantages of high power generation, large generation force, fast response speed, high durability, and low power consumption. Therefore, these advantages are utilized in inkjet printer heads and diesel engine injectors. Yes.

As such a piezoelectric / electrostrictive ceramic sintered body for a piezoelectric / electrostrictive actuator, a lead zirconate titanate {Pb (Zr, Ti) O ₃ , PZT} -based material has been used. Since the influence of the lead solute from the sintered body on the global environment is strongly concerned, alkali niobate-based materials have also been studied (for example, Patent Document 1, Non-Patent Documents 1 to 4). See).

  It is known that a PZT material, which is a typical piezoelectric / electrostrictive ceramic sintered body, has high piezoelectric characteristics at the phase boundary. The phase boundary is a state in which two or more crystal phases having the same composition but different crystal systems are mixed. For example, in the vicinity of Zr = Ti = 0.5, a tetragonal crystal and a rhombohedral crystal coexist (phase boundary), and the piezoelectric characteristics are enhanced.

  On the other hand, it is said that the characteristics of an alkali niobate-based piezoelectric / electrostrictive ceramic sintered body are enhanced at the phase boundary between tetragonal and orthorhombic. When the A site contains only K and Na, the phase boundary temperature between the tetragonal crystal and the orthorhombic crystal is 200 ° C. or higher, so the characteristics at room temperature are low, but the phase boundary is obtained by substituting Li for the A site. Since a study (see Non-Patent Document 3) in which the temperature is lowered and the characteristics near room temperature are improved (see Non-Patent Document 3), a composition containing Li has become the mainstream. In the analysis using the X-ray diffraction method, the crystal system of the perovskite oxide, which is the main crystal phase of the alkali niobate-based piezoelectric / electrostrictive ceramic sintered body, is tetragonal, orthorhombic, or tetragonal. An orthorhombic mixed crystal has been reported.

  Then, against the background of such a technical flow, in order to improve electrical characteristics, the degree of densification has been improved (for example, see Non-Patent Document 1) and element substitution (for example, see Non-Patent Document 3). ), And an attempt to improve the alignment structure (for example, see Non-Patent Document 4).

JP 2006-028001 A M.M. Matsubara et. al. , Jpn. J. et al. Appl. Phys. 44 (2005) p. 6136-6142. E. Hollenstein et. al. , Appl. Phys. Lett. 87 (2005) 182905. Y. Guo et. al. , App. Phys. Lett. 85 (2004) 4121 Y. Saito et. al. , Nature 432, 84-87 (2004)

  However, in the conventional alkaline niobate-based piezoelectric / electrostrictive ceramic sintered body, for example, the electric field induced strain S4000 is not always sufficient, and the electric characteristics such as the electric field induced strain are further improved. A piezoelectric / electrostrictive ceramic sintered body is desired. The present invention has been made in view of such circumstances, and it is an object of the present invention to find a new index or item that can be a factor for improving characteristics and propose a method for accurately evaluating it. Based on the results, an object is to provide an alkaline niobate-based piezoelectric / electrostrictive ceramic sintered body with improved electrical characteristics.

  As a result of repeated research, tetragonal crystals that have been recognized in the technical field of alkali / niobate-based piezoelectric / electrostrictive ceramic sintered bodies by precise measurement using a high-resolution X-ray diffractometer, or An unknown crystal phase (called third phase) other than orthorhombic perovskite oxide was discovered. This third phase is a crystal phase that has not been recognized in the technical field of alkali / niobate-based piezoelectric / electrostrictive ceramics sintered bodies. In addition, a means for easily quantifying the third phase with a general-purpose X-ray diffractometer has been found. Then, the correlation between the quantified third phase and the electrical characteristics was clarified, and this was used as a guideline for the development of an alkali niobate-based piezoelectric / electrostrictive ceramic sintered body. The present invention shown has been completed.

  That is, according to the present invention, a tetragonal perovskite oxide is the main crystal phase, and the asymmetry of the diffraction peak of the tetragonal (002) plane is 1 or more and 3.3 or less. An electrostrictive ceramic sintered body is provided.

An alkali niobate-based piezoelectric / electrostrictive ceramic sintered body according to the present invention has a composition formula ABO ₃ (A is at least one element selected from Li, Na, and K, and B is at least Nb, Ta. In other words, at least one ion selected from the group consisting of Li, Na, and K at the A site, and Nb at the B site. An alkali niobate-based piezoelectric / electrostrictive ceramic sintered body containing at least one kind of ions selected from the group consisting of Ta.

The main component of the alkali niobate-based piezoelectric / electrostrictive ceramics sintered body according to the present invention (also simply referred to as the piezoelectric / electrostrictive ceramics sintered body according to the present invention) is composed of the composition formula {Li _y (Na _1-x K _x ) _1-y } _a (Nb _1-z Ta _z ) O ₃ (where 0.90 ≦ a ≦ 1.10, 0.2 ≦ x ≦ 0.8, 0.00 ≦ y ≦ 0.10) , 0.00 ≦ z ≦ 0.50) is preferable.

The main component of the alkali niobate-based piezoelectric / electrostrictive ceramic sintered body according to the present invention is composed of the composition formula {Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−z−w Ta _z Sb _w ) O ₃ (provided that 0.90 ≦ a ≦ 1.10, 0.2 ≦ x ≦ 0.8, 0.00 ≦ y ≦ 0.10, 0.00 ≦ z ≦ 0.50, 0.00 <W ≦ 0.10) is preferable.

The main component of the piezoelectric / electrostrictive ceramics sintered body of the alkali niobate-based according to the present invention, the compositional formula _{[{Li y (Na 1-} x K x) 1-y} 1-t Bi t] a (Nb 1 _−z Ta _z ) O ₃ (where 0.90 ≦ a ≦ 1.10, 0.2 ≦ x ≦ 0.8, 0.00 ≦ y ≦ 0.10, 0.00 ≦ z ≦ 0.50, 0.00 <t ≦ 0.10) is preferable.

The main component of the alkali niobate-based piezoelectric / electrostrictive ceramic sintered body according to the present invention is composed of the composition formula {Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−z−w Ta _z Sb _w ) O ₃ + Bi ₂ O ₃ (provided that 0.90 ≦ a ≦ 1.10, 0.2 ≦ x ≦ 0.8, 0.00 ≦ y ≦ 0.10, 0.00 ≦ z ≦ 0.50) 0.00 <w ≦ 0.10, 0 <Bi ₂ O ₃ ≦ 5 mol%) is preferable.

  The alkali niobate-based piezoelectric / electrostrictive ceramic sintered body according to the present invention contains at least one metal element selected from the group consisting of Ag, Mn, Cr, Fe, Co, Ni, Cu, and Zn. Those that do are preferred. These metal elements are transition metal elements or typical metal elements, and belong to Groups 6 to 12 of the fourth period with similar chemical properties. These metal elements may be contained not only in the grain boundary phase but also in the grains or in different phases as oxides.

  The alkali niobate-based piezoelectric / electrostrictive ceramic sintered body according to the present invention contains at least one metal element selected from the group consisting of Ag, Mn, Cr, Fe, Co, Ni, Cu, and Zn. In this case, the content of the metal element is preferably 3 mol parts or less with respect to 100 mol parts of the main component. In other words, it is desirable that the metal elements as these subcomponents are contained so that the amount of addition in terms of metal atoms is 3 mol parts or less with respect to 100 mol parts of the perovskite oxide. The reason why the content is 3 mol parts or less is that when the content exceeds this range, the dielectric loss increases and the electric field induced strain at the time of applying a high electric field tends to decrease.

  As a means for obtaining an alkali niobate-based piezoelectric / electrostrictive ceramic sintered body having a diffraction peak asymmetry of a tetragonal crystal (002) plane of 1 or more and 3.3 or less, any of the preferred alkali niobate-based materials described above is used. (1) In the firing process, a firing keep process is added, (2) Polarization is performed at a high temperature of 50 ° C. or higher, and (3) Heat treatment is performed at a high temperature after polarization. (Aging treatment), (4) Composite composition.

  2. The alkali niobate-based piezoelectric / electrostrictive ceramic sintered body according to the present invention has a tetragonal perovskite oxide as the main crystal phase, and has a diffraction peak asymmetry of 1 or more in the tetragonal (002) plane. By setting it to 3 or less, excellent electrical characteristics (electric field induced strain, relative dielectric constant, piezoelectric constant, dielectric loss, etc.) can be obtained. A small degree of asymmetry means that the third phase is small. That is, the correlation between the third phase and the electrical characteristics of the alkaline niobate-based piezoelectric / electrostrictive ceramic sintered body is that the smaller the third phase, the better the electrical characteristics.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate, but the present invention should not be construed as being limited thereto. Various changes, modifications, improvements, and substitutions can be added based on the knowledge of those skilled in the art without departing from the scope of the present invention. For example, the drawings show preferred embodiments of the present invention, but the present invention is not limited by the modes shown in the drawings or the information shown in the drawings. In practicing or verifying the present invention, the same means as described in this specification or equivalent means can be applied, but preferred means are those described below.

  The alkali niobate-based piezoelectric / electrostrictive ceramic sintered body according to the present invention has an alkali niobate-based piezoelectric / electrostrictive whose tetragonal (002) plane has a diffraction peak asymmetry of 1 to 3.3. Ceramic sintered body. Therefore, first, an unknown third phase, its quantification means, and an asymmetry calculation method will be described below.

  (X-ray diffractometer 1) First, an X-ray diffractometer used for measuring an X-ray diffraction (XRD) profile will be described. For example, a high-resolution powder X-ray diffractometer composed mainly of four parts: an X-ray source (CuKα ray), a diffractive optical system, a detector, and a sample attachment is used. A Bragg-Brentano concentrated optical system (goniometer radius 250 mm) is used as the diffractive optical system, and a semiconductor system having sensitivity only to desired X-rays (CuKα rays) is used as the detector. The diverging slit is 0.5 °, the scattering slit is 0.5 °, and the light receiving slit is 0.1 mm. A sample attachment that can control the temperature of the sample from −20 ° C. to + 100 ° C. is used. The sample is cooled with liquid nitrogen. The sample is heated by a direct heating Pt heater, and the temperature is measured on the back side of the Pt heater to control the Pt heater.

  (XRD Profile Measurement Method 1) Next, an XRD profile measurement method using a high-resolution X-ray diffractometer will be described. To prevent condensation, the inside of the attachment is kept in a vacuum state. And after cooling to -20 degreeC and hold | maintaining for 5 minutes, an X-ray-diffraction (XRD) profile is measured. Thereafter, the temperature is raised at 4 ° C./minute, and after reaching a predetermined temperature, the temperature is held for 5 minutes, and then the XRD profile is measured. While repeating this, the XRD profile is measured up to + 100 ° C. When the temperature reaches room temperature or higher, the vacuum is broken to atmospheric pressure. The XRD profile is measured by measuring the X-ray diffraction profile of the surface of an alkali niobate-based piezoelectric / electrostrictive ceramic sintered body at a temperature of −20 ° C. to + 100 ° C. by 2θ / θ scanning. The width of the 2θ / θ scan is preferably 0.02 ° or 0.01 °.

  However, the configuration of the high-resolution X-ray diffractometer described here is only an example, and other configurations may be adopted as long as the X-ray diffraction profile can be measured with sufficient resolution and accuracy. Good.

  (Analysis 1 of XRD Profile) FIG. 1 is an XRD profile of a typical alkali niobate-based piezoelectric / electrostrictive ceramic sintered body measured using the above-described high-resolution X-ray diffractometer. At first glance, the XRD profile in FIG. 1 can be determined as a single phase of tetragonal perovskite oxide. However, when observed in detail, in addition to the tetragonal perovskite oxide, an unknown phase (third phase) that has not been recognized so far could be confirmed. That is, an unknown peak (see FIG. 1) was present on the high angle side of the diffraction peak of the tetragonal (002) plane. This is not the diffraction peak of the (002) plane due to the CuKα2 line due to the intensity ratio and 2θ angle. This unknown peak may be attributed to the orthorhombic perovskite oxide. However, from the XRD profile measured at room temperature or lower, the orthorhombic peak does not appear at the angle of the previous unknown peak, and the diffraction peaks of the orthorhombic (022) plane and (200) plane are higher than the unknown peak. Appeared to the side. From these facts, the unknown peak does not indicate an orthorhombic perovskite oxide. And in the sintered niobate-based piezoelectric / electrostrictive ceramics, this unknown peak was detected regardless of the composition ratio and the presence / absence / type of substitution / addition elements. It is considered that this is a crystal phase peculiar to an alkali niobate-based piezoelectric / electrostrictive ceramic sintered body.

  (X-ray diffractometer 2) The third phase can be detected even by a general-purpose powder X-ray diffractometer. For example, a powder X-ray diffractometer mainly composed of four parts of an X-ray source (CuKα ray), a diffractive optical system, a monochromator, and a detector is used. This is one of the most popular device configurations in general. As a diffractive optical system, a Bragg-Brentano concentrated optical system (goniometer radius 185 mm) is used. A counter monochromator (the crystal is curved graphite) is installed between the sample and the detector. This is for removing as much as possible extra X-rays (continuous X-rays, fluorescent X-rays, Kβ rays, etc.) other than CuKα rays. The diverging slit is 1 °, the scattering slit is 1 °, and the light receiving slit is 0.3 mm.

  (XRD Profile Measurement Method 2) Next, an XRD profile measurement method using a general-purpose X-ray diffractometer will be described. The XRD profile is measured by measuring the X-ray diffraction profile of the surface of the alkali niobate-based piezoelectric / electrostrictive ceramic sintered body at room temperature by 2θ / θ scanning. The width of the 2θ / θ scan is preferably 0.02 ° or 0.01 °.

  However, the configuration of the general-purpose X-ray diffractometer described here is only an example, and other configurations may be adopted as long as the X-ray diffraction profile can be measured with the same resolution and accuracy. .

  (Analysis 2 of XRD Profile) FIG. 2 is an XRD profile of a typical alkali niobate-based piezoelectric / electrostrictive ceramic sintered body measured using the general-purpose X-ray diffractometer (background is shown). Removed). FIG. 2 is an XRD profile of the same sintered body as in FIG. In FIG. 2, unlike FIG. 1, the unknown peak could not be detected clearly. However, the presence of the peak was confirmed. That is, the peak swelled from the peak top to the high angle side of the diffraction peak of the tetragonal crystal (002) plane (see FIG. 2). The bulge of the peak on the high angle side is also influenced by the CuKα2 line. However, it was much larger than the bulge on the high angle side of the diffraction peak of the tetragonal (200) plane at a 2θ angle close to the diffraction peak of the tetragonal (002) plane. This difference clearly indicates the presence of the third phase. Therefore, the third phase can be quantified by quantifying this.

(Quantification of the third phase: calculation of the degree of asymmetry) First, as described above, an XRD profile is measured using an X-ray diffractometer having the same resolution and accuracy as the general-purpose X-ray diffractometer. . Next, with respect to the XRD profile, the background is removed by calculation processing, and as shown in FIG. 2, a line immediately below each diffraction peak top of the tetragonal crystal (002) and (200) planes (dotted line in FIG. 2). )pull. Then, the half width of each peak is measured, and these are set as W ₁ and W _2, and the width on the low angle side is set as W (L) ₁ and W (L) ₂ from the line drawn directly from the top of each diffraction peak. The width on the high angle side is W (H) ₁ and W (H) ₂ . That is, W (L) ₁ + W (H) ₁ = W ₁ , W (L) ₂ + W (H) ₂ = W ₂ . Next, the asymmetry degree of the diffraction peak of the tetragonal crystal (002) plane is obtained using the following formula (also refer to FIG. 2). By dividing by the ratio of W (L) ₂ and W (H) _{2 on} the tetragonal (200) plane, it is possible to easily correct the asymmetry due to the CuKα2 line. When the degree of asymmetry is 1, there is no third phase, and it can be determined that the third phase increases as the degree of asymmetry is greater than 1.
Asymmetry = (W (H) ₁ / W (L) ₁ ) / (W (H) ₂ / W (L) ₂ )

  Next, an example of the method for producing an alkali niobate-based piezoelectric / electrostrictive ceramic sintered body according to the present invention will be described.

  First, a piezoelectric / electrostrictive ceramic powder (calcined / ground powder) is manufactured. The compound containing each metal element is weighed so as to satisfy the ratio (molar ratio) of each metal element in the composition of the piezoelectric / electrostrictive ceramic powder, and mixed with a solvent such as ethanol by a mixing method such as a ball mill. A mixed slurry is obtained. In addition, although the kind of compound containing each metal element is not particularly limited, an oxide, carbonate, or tartrate of each metal element is preferably used. For example, lithium carbonate, potassium tartrate, sodium tartrate, Niobium oxide and tantalum oxide can be used. Next, the obtained mixed slurry is dried by using a drier or by an operation such as filtration, and calcined and pulverized. The pulverization may be performed by a method such as a ball mill. In this way, a piezoelectric / electrostrictive ceramic powder (calcined / ground powder) is produced.

  The average particle diameter of the piezoelectric / electrostrictive ceramic powder (calcined / ground powder) is preferably 0.1 μm or more and 1 μm or less. Here, the average particle diameter is a 50% diameter (median diameter) in the cumulative distribution. Moreover, it is preferable to add at least one metal element selected from the group consisting of Ag, Mn, Cr, Fe, Co, Ni, Cu, and Zn to the calcined / ground powder.

  Next, the calcined / ground powder is formed into a pellet and fired. The maximum temperature during firing is preferably 950 to 1100 ° C., and the time for maintaining the maximum temperature is preferably 0.5 to 6 hours. Firing is preferably performed by performing a firing keeping step of maintaining at a constant temperature in the range of 800 to 950 ° C. for a certain period of time in the temperature raising process, and then further heating and sintering at the firing temperature. More preferably, it is good to maintain for a fixed time of 0.5 to 20 hours in a baking keep process. In particular, the range of a keep temperature of 800 to 900 ° C. is more preferable.

  Thereafter, the obtained sintered body is processed into an appropriate shape (for example, strip shape) as necessary, and then subjected to polarization treatment. The polarization treatment is performed by applying a voltage of about 5 kV / mm for 15 minutes or more.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

(Comparative Example _{1) {Li y (Na 1} -x K x) 1-y} a (Nb 1-z Ta z) O 3 (x = 0.450, y = 0.060, z = 0.082, a = 1.01) +0.02 mol% MnO ₂ calcined / ground powder (particle size 0.2 to 0.5 μm, particle shape is spherical) is formed into pellets to obtain a pellet sample A It was. The pellet-like sample A was heated to a firing temperature of 970 ° C. at a rate of 200 ° C./h in the atmosphere, held at 970 ° C. for 3 hours, and then cooled to room temperature at a rate of 200 ° C./h. An electrostrictive ceramic sintered body was obtained.

  Next, XRD profiles on both the front and back surfaces of the obtained piezoelectric / electrostrictive ceramic sintered body were measured, and asymmetry 1 (asymmetry before polarization) was calculated. The average of the front and back was set to 1 asymmetry.

  Next, the piezoelectric / electrostrictive ceramic sintered body was processed into a strip shape, and then heat-treated at 600 ° C. for 1 hour in the air to remove the processing stress. And the polarization process was performed for 15 minutes by the voltage of 5 kV / mm in the silicon oil hold | maintained at 25 degreeC, and the electrical property (electric field induced strain S4000) was evaluated. The electric field induced strain S4000 is a strain amount in 31 directions (a direction perpendicular to the electric field application direction) when an electric field of 4 kV / mm is applied. Next, the XRD profiles of the front and back surfaces of the strip-shaped sample after the electrical property evaluation were measured, and the asymmetry 2 (the asymmetry after polarization) was calculated. The average of the front and back sides was set to 2 asymmetry. Table 1 shows the degree of asymmetry 1 and 2 and the electric field induced strain S4000.

  (Examples 1 to 3) The pellet-like sample A obtained in the same manner as in Comparative Example 1 was heated to 850 ° C. at a rate of 200 ° C./h in the atmosphere, and at 850 ° C. for 3 hours (Example 1) 6 hours (Example 2) and 10 hours (Example 3), respectively, and after carrying out the baking keep step, the temperature was raised to a baking temperature of 970 ° C. at a rate of 200 ° C./h, and then at 970 ° C. for 3 hours. After being held, it was cooled to room temperature at a rate of 200 ° C./h to obtain a piezoelectric / electrostrictive ceramic sintered body.

  Next, the degree of asymmetry 1 was calculated in the same manner as in Comparative Example 1. Subsequently, after processing, heat treatment, and polarization treatment, the electrical characteristics were evaluated, and the degree of asymmetry 2 was calculated. Table 1 shows firing keeping conditions (temperature and time), asymmetry degree 1 and 2, and electric field induced strain S4000.

(Comparative Example _{2) {Li y (Na 1} -x K x) 1-y} a (Nb 1-z-w Ta z Sb w) O 3 (x = 0.450, y = 0.060, z = 0.082, a = 1.01, w = 0.040) +0.02 mol% MnO ₂ calcined / ground powder (particle size 0.2-0.5 μm, particle shape is spherical) in pellet form And pelletized sample B was obtained. The pellet-like sample B was heated in the atmosphere to a firing temperature of 980 ° C. at a rate of 200 ° C./h, held at 980 ° C. for 3 hours, and then cooled to room temperature at a rate of 200 ° C./h. An electrostrictive ceramic sintered body was obtained.

  Next, asymmetry 1 was calculated in the same manner as in Comparative Example 1. Next, the piezoelectric / electrostrictive ceramic sintered body was processed into a strip shape, and then heat-treated at 900 ° C. for 1 hour in the air to remove the processing stress. Then, polarization treatment was performed for 15 minutes at a voltage of 5 kV / mm in silicon oil maintained at 25 ° C., and the electrical characteristics were evaluated in the same manner as in Comparative Example 1 to calculate the degree of asymmetry 2. Table 2 shows the polarization temperature, the degree of asymmetry 1, 2 and the electric field induced strain S4000.

  (Example 4) The pellet-like sample B obtained in the same manner as in Comparative Example 2 was heated to 880 ° C at a rate of 200 ° C / h in the atmosphere and held at 880 ° C for 3 hours. After the heating, the temperature was raised to 980 ° C. at a rate of 200 ° C./h, held at 980 ° C. for 3 hours, then cooled to room temperature at a rate of 200 ° C./h to obtain a piezoelectric / electrostrictive ceramic sintered body. Obtained.

  Next, as in Comparative Example 2, the degree of asymmetry 1 was calculated, followed by processing and heat treatment, followed by polarization treatment for 15 minutes at a voltage of 5 kV / mm in silicon oil maintained at 80 ° C. It was. Subsequently, heat treatment (aging treatment) was performed at 250 ° C. for 12 hours in the air. Then, in the same manner as in Comparative Example 1, the electrical characteristics were evaluated, and the degree of asymmetry 2 was calculated. Table 2 shows firing keep conditions (temperature and time), polarization temperature, aging conditions (temperature and time), asymmetry 1 and 2, and electric field induced strain S4000.

(Comparative Example _{3) [{Li y (Na} 1-x K x) 1-y} 1-t Bi t] a (Nb 1-z Ta z) O 3 (x = 0.450, y = 0.060 , Z = 0.082, a = 1.01, t = 0.0005) + 0.05 mol% MnO ₂ calcined / ground powder (particle size 0.2 to 0.5 µm, particle shape is spherical) ) Was formed into a pellet, and a pellet-like sample C was obtained. The pellet-like sample C was heated to a firing temperature of 970 ° C. at a rate of 200 ° C./h in the atmosphere, held at 970 ° C. for 3 hours, and then cooled to room temperature at a rate of 200 ° C./h. An electrostrictive ceramic sintered body was obtained.

  Next, asymmetry 1 was calculated in the same manner as in Comparative Example 1. Next, the piezoelectric / electrostrictive ceramic sintered body was processed into a strip shape, and then heat treated at 900 ° C. for 1 hour in the air to remove the processing stress. And the polarization process was performed for 15 minutes at the voltage of 5 kV / mm in the silicone oil hold | maintained at 25 degreeC, it carried out similarly to the comparative example 1, the electrical property was evaluated, and the asymmetry degree 2 was computed. Table 3 shows the polarization temperature, the degree of asymmetry 1, 2 and the electric field induced strain S4000.

  (Example 5) The pellet-like sample C obtained in the same manner as in Comparative Example 3 was heated to 850 ° C at a rate of 200 ° C / h in the atmosphere and held at 850 ° C for 4 hours. Then, the temperature was raised to a firing temperature of 970 ° C. at a rate of 200 ° C./h, held at 970 ° C. for 3 hours, and then cooled to room temperature at a rate of 200 ° C./h to obtain a piezoelectric / electrostrictive ceramic sintered body. Obtained.

  Next, the degree of asymmetry 1 was calculated in the same manner as in Comparative Example 3, followed by processing and heat treatment, followed by polarization treatment for 15 minutes at a voltage of 5 kV / mm in silicon oil maintained at 75 ° C. It was. Subsequently, heat treatment (aging treatment) was performed at 150 ° C. for 12 hours in the air. Then, in the same manner as in Comparative Example 1, the electrical characteristics were evaluated, and the degree of asymmetry 2 was calculated. Table 3 shows firing keeping conditions (temperature and time), polarization temperature, aging conditions (temperature and time), asymmetry 1 and 2, and electric field induced strain S4000.

(Comparative Example _{4) {Li y (Na 1} -x K x) 1-y} a (Nb 1-z Ta z) O 3 (x = 0.450, y = 0.060, z = 0.082, A calcined / ground powder (particle size: 0.2 to 0.5 μm, particle shape is spherical) having a composition of a = 1.01) was formed into a pellet shape, and a pellet-shaped sample D was obtained. The pellet-like sample D was heated to a firing temperature of 1000 ° C. at a rate of 200 ° C./h in the atmosphere, held at 1000 ° C. for 3 hours, and then cooled to room temperature at a rate of 200 ° C./h. An electrostrictive ceramic sintered body was obtained.

  Next, asymmetry 1 was calculated in the same manner as in Comparative Example 1. Next, the piezoelectric / electrostrictive ceramic sintered body was processed into a strip shape, and then heat treated at 900 ° C. for 1 hour in the air to remove the processing stress. Then, in the same manner as in Comparative Example 1, after performing the polarization treatment, the electrical characteristics were evaluated, and the degree of asymmetry 2 was calculated. Table 4 shows the degree of asymmetry 1 and 2 and the electric field induced strain S4000.

(Examples 6 and 7) {Li _y (Na _1-x K _x ) _1-y } _a (Nb _1-z Ta _z ) O ₃ (x = 0.450, y = 0.060, z = 0. 082, a = 1.01) calcined / ground powder (base material raw material powder) and {Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−z Ta _z ) O ₃ A calcined / ground powder (additive material powder) having a composition of (x = 0.450, y = 0.060, z = 0.082, a = 1.01) +0.02 mol% MnO ₂ was prepared. The particle size of the base material powder was 0.2 to 0.5 μm, and the particle size of the additive material powder was 1 to 2 μm. And with respect to a base material raw material powder, after adding an additive so that it might become 20 vol% (Example 6) and 40 vol% (Example 7), respectively, after dry-mixing, it shape | molds in a pellet form, pellet form A sample was obtained. These pellet-like samples were heated to a firing temperature of 1000 ° C. at a rate of 200 ° C./h in the atmosphere, held at 1000 ° C. for 3 hours, then cooled to room temperature at a rate of 200 ° C./h, and piezoelectric / electrical A strain ceramic sintered body was obtained.

  Next, the degree of asymmetry 1 was calculated in the same manner as in Comparative Example 4, followed by processing, heat treatment, and polarization treatment, the electrical characteristics were evaluated, and the degree of asymmetry 2 was calculated. Table 4 shows the amount of additive raw material powder, the degree of asymmetry 1 and 2 and the electric field induced strain S4000.

  Tables 1 to 4 show relationships among manufacturing conditions, asymmetry, and piezoelectric characteristics. From the results of Examples 1 to 7 and Comparative Examples 1 to 4 shown in Tables 1 to 4, the asymmetry (asymmetry 1 and 2) is made close to 1, that is, by reducing the third phase, for example, the electric field It can be seen that electrical characteristics such as the induced strain S4000 can be improved. As means for reducing the degree of asymmetry close to 1, that is, reducing the third phase, a firing keeping process, high temperature polarization, high temperature aging treatment, and composition composition are effective.

  The alkali niobate-based piezoelectric / electrostrictive ceramic sintered body according to the present invention exhibits excellent electric field-induced strain, and is a piezoelectric / electrostrictive element (piezoelectric / electrostrictive body) constituting an actuator, a sensor or the like. It is suitably used as a material.

It is an XRD profile of a typical alkali niobate-based piezoelectric / electrostrictive ceramic sintered body measured using a high-resolution X-ray diffractometer. It is an XRD profile of a typical alkali niobate-based piezoelectric / electrostrictive ceramic sintered body measured using a general-purpose X-ray diffractometer.

Claims (7)

  Tetragonal perovskite containing at least one element selected from the group consisting of Li, Na and K as an A site constituent element and at least one element selected from the group consisting of Nb and Ta as a B site constituent element A piezoelectric / electrostrictive ceramics sintered body having a type oxide as a main crystal phase and a diffraction peak of tetragonal (002) plane having an asymmetry of 1 or more and 3.3 or less. The composition of the main component general formula _{{Li y (Na 1-x} K x) 1-y} a (Nb 1-z Ta z) O 3 ( where, 0.90 ≦ a ≦ 1.10,0.2 ≦ The piezoelectric / electrostrictive ceramic sintered body according to claim 1, wherein x ≦ 0.8, 0.00 ≦ y ≦ 0.10, and 0.00 ≦ z ≦ 0.50). The composition of the main component is the general formula {Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−z−w Ta _z Sb _w ) O ₃ (where 0.90 ≦ a ≦ 1.10, The piezoelectric device according to claim 1, wherein 0.2 ≦ x ≦ 0.8, 0.00 ≦ y ≦ 0.10, 0.00 ≦ z ≦ 0.50, 0.00 <w ≦ 0.10). / Electrostrictive ceramic sintered body. The composition of the main component is the general formula [{Li _y (Na _1−x K _x ) _1−y } _{1−t B i t} ] _a (Nb _1−z Ta _z ) O ₃ (where 0.90 ≦ a ≦ 1 .10, 0.2 ≦ x ≦ 0.8, 0.00 ≦ y ≦ 0.10, 0.00 ≦ z ≦ 0.50, 0.00 <t ≦ 0.10) The piezoelectric / electrostrictive ceramic sintered body described. The composition of the main component general formula _{{Li y (Na 1-x} K x) 1-y} a (Nb 1-z-w Ta z Sb w) O 3 + Bi 2 O 3 ( where, 0.90 ≦ a ≦ 1.10, 0.2 ≦ x ≦ 0.8, 0.00 ≦ y ≦ 0.10, 0.00 ≦ z ≦ 0.50, 0.00 <w ≦ 0.10, 0 <Bi ₂ O ₃ The piezoelectric / electrostrictive ceramic sintered body according to claim 1, represented by: ≦ 5 mol%.   The piezoelectric / electrostrictive according to any one of claims 1 to 5, further comprising at least one metal element selected from the group consisting of Ag, Mn, Cr, Fe, Co, Ni, Cu, and Zn. Ceramic sintered body.   The piezoelectric / electrostrictive ceramic sintered body according to claim 6, wherein the content of the metal element is 3 mol parts or less with respect to 100 mol parts of the main component.

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