JP6195110B2 - Oxide ceramics and ceramic electronic parts - Google Patents

Description

  The present invention relates to oxide ceramics and ceramic electronic components, and more particularly, oxide ceramics formed of a ferromagnetic dielectric material exhibiting an electromagnetic effect, and ceramic electronic components such as variable inductors using the oxide ceramics. About.

  In recent years, ferromagnetic dielectric materials (multiferroics) in which ferromagnetism and ferroelectricity coexist and exhibit a combined action have attracted attention and are actively researched and developed.

  This ferromagnetic dielectric material induces a helical magnetic order when a magnetic field is applied to cause electrical polarization, changes in electrical polarization and dielectric constant, and magnetization occurs or changes in magnetization when an electric field is applied. It is known to exhibit a so-called electromagnetic effect.

  Since the ferromagnetic dielectric material can cause a change in magnetization due to an electric field or a change in electric polarization due to a magnetic field due to the above-described electromagnetic effect, a novel and useful inductor or actuator that utilizes both magnetization and electric polarization. Realization of various ceramic electronic parts such as power generation elements is expected.

Patent Document 1 discloses a general formula (Sr _1-α Ba _α ) ₃ (Co _1-β B _β ) ₂ Fe ₂₄ O _{41 + δ} (wherein B represents Ni, Zn, Mn, Mg And one or more elements selected from the group consisting of Cu and α, β, and δ are 0 ≦ α ≦ 0.3, 0 ≦ β ≦ 0.3, and −1 ≦ δ ≦ 1, respectively. An electromagnet effect material having an electromagnetism effect in a temperature range of 250 to 350 K and a magnetic field range of 0.05 T (Tesla) or less is proposed.

  In this Patent Document 1, by using a ferromagnetic dielectric material having a hexagonal Z-type crystal structure represented by the above general formula, the insulating property is good even at a weak magnetic field of about 0.05 T or less near the room temperature. A ferromagnetic dielectric material having an electromagnetic effect is being obtained.

JP 2012-1396 A (Claim 1, paragraph number [0010], Tables 1 to 3 etc.)

  However, since the ferromagnetic dielectric material described in Patent Document 1 can obtain a relatively high electric polarization at room temperature (25 ° C.), it can obtain a good electromagnetic effect, and also has a comparison in insulation performance. However, when the above-mentioned ferromagnetic dielectric material is used for a ceramic electronic component such as a variable inductor, the temperature characteristics of the magnetic permeability are inferior, and the magnetic permeability greatly fluctuates due to changes in the ambient temperature. There was a problem that it fluctuated greatly depending on the ambient temperature.

  The present invention has been made in view of such circumstances, and oxide ceramics that can improve the temperature characteristics of magnetic permeability without impairing ferromagnetic dielectric properties such as insulation performance and electric polarization, and the An object of the present invention is to provide a ceramic electronic component using oxide ceramics.

As a result of intensive research on the Sr ₃ Co ₂ Fe ₂₄ O _41- based compound that is considered promising as a ferromagnetic dielectric material, the present inventors include predetermined amounts of Si and Mg in the oxide ceramics. As a result, it has been found that the temperature characteristics of the magnetic permeability can be improved without impairing the ferromagnetic dielectric characteristics such as the insulation performance and the electric polarization.

In addition, the Sr ₃ Co ₂ Fe ₂₄ O _41- based compound typically has a hexagonal Z-type crystal structure, but even if it is a crystal system having lower symmetry than the hexagonal system, at least Sr in the main component. It was found that the same effect can be obtained by adding a predetermined amount of Si and Mg in the case of a ferrite compound containing Co, Co, and Fe.

  The present invention has been made based on these findings, and the oxide ceramic according to the present invention has a main component formed of a ferrite compound containing at least Sr, Co, and Fe, and Si is the main component. In contrast, it is contained in a range of 0.01 to 0.2 in terms of a molar ratio x, and Mg is contained in a form in which a part of the Fe is substituted, and the Mg in the main component The content of is characterized by being 0.03 to 0.3 in terms of a molar ratio y.

Further, the oxide ceramic of the present invention has a general formula [Sr ₃ Co ₂ Fe _24-y Mg _y O ₄₁ —xSiO ₂ ] (where 0.01 ≦ x ≦ 0.2, 0.03 ≦ y ≦ 0. It is preferable to be represented by 3).

  In the oxide ceramic of the present invention, it is also preferable that a part of the Sr is substituted with Ba.

  The ceramic electronic component according to the present invention is a ceramic electronic component in which an external electrode is formed on a surface of a component element body, wherein the component element body is formed of the oxide ceramic. .

  In the ceramic electronic component of the present invention, it is preferable that the coil is arranged so as to have an inductance corresponding to the magnetic permeability of the component element body.

  As a result, various ceramic electronic components such as variable inductors utilizing ferromagnetic dielectric properties can be easily obtained.

  Furthermore, in the ceramic electronic component of the present invention, it is preferable that the internal electrode is embedded in the component element body.

  According to the oxide ceramics of the present invention, the main component is formed of a ferrite compound containing at least Sr, Co, and Fe, and Si is converted to a molar ratio x of 0.01 to 0.01 to the main component. It is contained in the range of 0.2, Mg is contained in a form in which a part of the Fe is substituted, and the content of Mg in the main component is 0.00 in terms of a molar ratio y. Since it is 03-0.3, the temperature characteristic of a magnetic permeability can be improved, without impairing ferromagnetic dielectric characteristics, such as insulation performance and an electric polarization.

  Moreover, according to the ceramic electronic component of the present invention, a ceramic electronic component in which external electrodes are formed on the surface of the component element body, wherein the component element body is formed of any of the oxide ceramics described above. Therefore, it is possible to obtain a ceramic electronic component such as a variable inductor capable of improving the temperature characteristic of the magnetic permeability without impairing the ferromagnetic dielectric characteristics such as the insulation performance and the electric polarization.

It is a front view which shows one Embodiment of the ceramic electronic component formed using the oxide ceramics based on this invention. It is sectional drawing of FIG. It is the perspective view which showed typically the polarization processing apparatus used in the Example. It is the perspective view which showed typically the characteristic evaluation apparatus used in the Example. It is a figure which shows the current density characteristic in sample number 16, and an electric polarization characteristic. It is a figure which shows the relationship between the magnetic field in sample number 16, and magnetic flux density. It is a figure which shows the temperature characteristic of the magnetic permeability of the sample number. It is a figure which shows the temperature characteristic of the magnetic permeability of the sample number.

  Next, an embodiment of the present invention will be described in detail.

  The oxide ceramic according to one embodiment of the present invention is formed of a ferrite compound containing Sr, Co, and Fe as a main component, and Si is converted to a molar ratio x of 0 with respect to the main component. 0.01 to 0.2, Mg is contained in a form in which a part of the Fe is substituted, and the content of Mg in the main component is converted into a molar ratio y. 0.03-0.3.

Specifically, the oxide ceramic of the present invention is mainly composed of a Sr ₃ Co ₂ Fe ₂₄ O ₄₁ ((SrO) ₃ (CoO) ₂ (Fe ₂ O ₃ ) ₁₂ ) -based compound having a hexagonal Z-type crystal structure. As a component, it can be represented by the following general formula (A).

_{Sr 3 Co 2 Fe 24-y} Mg y O 41 -xSiO 2 ... (A)
Here, x represents the molar ratio of SiO _{2 to} Sr ₃ Co ₂ Fe _24-y Mg _y O ₄₁ , and x and y satisfy the formulas (1) and (2).

0.01 ≦ x ≦ 0.2 (1)
0.03 ≦ y ≦ 0.3 (2)
As described above, the present oxide ceramics is an oxide having a good temperature characteristic of magnetic permeability without impairing the insulating performance and the ferromagnetic dielectric characteristics when the general formula (A) satisfies the formulas (1) and (2). It becomes possible to obtain ceramics.

As described in detail in Non-Patent Document 1, the hexagonal Z-type crystal structure has three different blocks, R block, S block, and T block, which are R-S-T-S-R ^* -S ^* - It has a complicated crystal structure laminated in the order of T ^* -S ^* . Note that * indicates a block rotated by 180 ° with respect to the c-axis. For example, in the case of Sr ₃ Co ₂ Fe ₂₄ O ₄₁ , when each block is defined by a chemical formula, the R block is composed of [SrFe ₆ O ₁₁ ] ²⁻ and the S block is composed of Co ₂ ²⁺ Fe ₄ O _8. The T block is composed of Sr ₂ Fe ₈ O ₁₄ . _{Then, Sr 3 Co 2 Fe 24 O} 41 , the above blocks are a multilayer structure having a lamination period laminated in the order of R-S-T-S ····· .

Robert C. Pullar, “Hexagonal Ferrites: A review of the synthesis, properties and applications of hexaferrite ceramics”, Progress in Materials Science 57, 2012, pp. 1191-1334

The Sr ₃ Co ₂ Fe ₂₄ O _41- based compound having this hexagonal Z-type crystal structure is considered promising as a ferromagnetic dielectric material that can simultaneously obtain ferromagnetism and ferroelectricity. The electric polarization can be generated by applying the magnetic field, and the change of magnetization can be generated by applying the electric field.

Since the Sr ₃ Co ₂ Fe ₂₄ O _41- based compound described in Patent Document 1 has high electrical polarization and good insulation performance at room temperature, variable inductors and other coil elements utilizing both magnetization and electrical polarization are used. Application to various ceramic electronic parts is expected.

However, as described in [Problems to be Solved by the Invention], when the Sr ₃ Co ₂ Fe ₂₄ O _41- based compound described in Patent Document 1 is used for a ceramic electronic component such as a variable inductor, the permeability is low. It is inferior in temperature characteristics, and the magnetic permeability varies greatly depending on the ambient temperature, and the inductance of the coil varies greatly. Therefore, it is difficult to obtain sufficient reliability.

  Therefore, in the present embodiment, Si and Mg are contained in the oxide ceramic so that the general formula (A) satisfies the formulas (1) and (2), thereby improving the insulating performance and the ferromagnetic dielectric characteristics. An oxide ceramic having good magnetic permeability temperature characteristics is obtained without loss.

  The reason why the temperature characteristic of the magnetic permeability is improved is considered to be as follows.

In general, it is known that when a Si compound containing tetravalent Si typified by SiO ₂ is added to oxide ceramics, Si exists at the grain boundary and acts as a sintering aid.

However, according to the research results of the present inventors, it has been found that when the Si compound is added to the Sr ₃ Co ₂ Fe ₂₄ O _41- based compound, the specific resistance ρ decreases and the insulating performance deteriorates. This is because most of the tetravalent Si is present at the crystal grain boundaries, but a part of the Si is dissolved in the Fe site containing trivalent Fe as a main component in the vicinity of the crystal grain boundaries, and the charge balance is lost. It is presumed that.

  Therefore, the present inventors have made further studies, and by adding a predetermined amount of a Mg compound containing divalent Mg in addition to a predetermined amount of Si, it is possible to compensate for the charge balance. It was found that the temperature characteristics of the magnetic permeability can be improved without impairing the characteristics. That is, when a Si compound is added to the oxide ceramic, a part of Si dissolves in the Fe site and the charge balance is lost. However, by adding the Mg compound, divalent Mg becomes a part of Fe. It is considered that the substitutional solution forms a solid solution at the Fe site, thereby compensating the charge balance and improving the temperature characteristic of the magnetic permeability.

  Next, the reason why the molar ratio x of Si to the main component and the molar ratio y of Mg satisfy Expressions (1) and (2) will be described.

(1) Si molar ratio x
As described above, by containing Si together with Mg, the temperature characteristic of the magnetic permeability can be improved by these synergistic effects. For this purpose, the molar ratio x to the main component is at least 0.01 in terms of oxide. The above is necessary.

  However, when the molar ratio x exceeds 0.2 and Si is excessively contained, even if Mg is contained, the specific resistance ρ is remarkably lowered, which may cause deterioration of the insulation performance.

  That is, if Mg is excessively contained in the oxide ceramics, there is a possibility that the electromagnetic characteristics may be deteriorated. Therefore, even if Mg is contained, it is necessary to limit it to a predetermined range so as to satisfy the above (2). is there.

  However, when Mg is contained in a range that satisfies the above (2), if the molar ratio x exceeds 0.2 and Si is contained, the Si content becomes excessive and the charge balance is sufficiently compensated. For this reason, the specific resistance ρ is lowered, and there is a possibility that the insulation performance is deteriorated.

  Therefore, in the present embodiment, Si is contained so that the molar ratio x is 0.01 to 0.2 in terms of oxide.

(2) Mg molar ratio y
As described above, Mg is solid-dissolved in the main component in a form in which Mg is replaced with a part of Fe, so that the charge balance can be compensated even if Si is contained. Can be improved. For this purpose, the molar ratio y of Mg replacing part of Fe is required to be at least 0.03 or more.

  However, when the molar ratio y exceeds 0.3, the electric polarization P decreases, and the desired electromagnetic effect cannot be obtained as described above.

  Therefore, in the present embodiment, Mg is contained so that the molar ratio y is 0.03 to 0.3.

  That is, in the above general formula (A), when the molar ratio x of Si and the molar ratio y of Mg satisfy the above mathematical expressions (1) and (2), the magnetic permeability can be obtained without impairing the insulating performance and the electromagnetic effect. The temperature characteristics can be improved.

Specifically, the temperature change is within the range of +10 to + 35 ° C. while ensuring good insulation performance with a specific resistance ρ of 100 MΩ · cm or more and a good electromagnetic effect with an electric polarization P of 10 μC / m ² or more. Even if it occurs, it is possible to obtain an oxide ceramic with good temperature characteristics of magnetic permeability that can suppress the change rate Δμ of magnetic permeability to 35% or less.

  In the above embodiment, the ferrite compound having a hexagonal Z-type structure having the lamination period of the R block, S block, and T block has been described in detail. However, the periodic structure of the lamination period is partially broken, and the crystal symmetry is reduced. A crystal system lower than the hexagonal system may be used.

In addition, a crystal system in which ions coordinated at a predetermined atomic position of the crystal lattice are slightly displaced from the predetermined atomic position and the symmetry of the crystal is lower than that of the hexagonal system. For example, in a hexagonal Z-type crystal structure, ^ions such as O ²⁻ and Co ²⁺ constituting the crystal are arranged at predetermined atomic positions where the space group describing the symmetry of the crystal is defined by P6 ₃ / mmc. The However, the present invention provides a crystal structure in which the ions move from the predetermined atomic position and are arranged at atomic positions defined by other space groups, and the symmetry of the crystal is lower than that of the hexagonal system. Is also applicable.

  That is, in the present oxide ceramics, it is important that the ferrite compound containing at least Sr, Co, and Fe contains the above-mentioned predetermined amounts of Si and Mg, and the crystal symmetry is slightly lower than that of the hexagonal system. Even the system can achieve the intended purpose of the present invention.

  Next, the manufacturing method of this oxide ceramic is explained in full detail.

First, as a ceramic raw material, an Fe compound such as Fe ₂ O ₃ , an Sr compound such as SrCO ₃ , a Co compound such as Co ₃ O ₄ , an Mg compound such as MgCO ₃ , and an Si compound such as SiO ₂ are prepared.

  And each ceramic raw material is weighed so that the said general formula (A) may satisfy | fill numerical formula (1), (2).

  Next, these weighed ceramic raw materials are put into a pulverizer such as a pot mill together with a pulverizing medium such as partially stabilized zirconium (hereinafter referred to as “PSZ”) balls, a dispersant and a solvent such as pure water. Mix and grind to obtain a mixture.

  Next, after drying and sizing the mixture, the mixture is calcined at 1000 to 1100 ° C. in an air atmosphere for a predetermined time to obtain a calcined product.

  Next, after sizing this calcined product, it is again put into a pulverizer together with a pulverizing medium, a dispersant, and an organic solvent such as ethanol and toluene, sufficiently mixed and pulverized, and then a binder solution is added sufficiently. To obtain a ceramic slurry.

  The binder solution is not particularly limited. For example, an organic binder such as polyvinyl butyral resin is dissolved in an organic solvent such as ethanol or toluene, and an additive such as a plasticizer is added as necessary. can do.

  Next, the ceramic slurry thus formed is formed into a sheet shape using a forming method such as a doctor blade method, and cut into a predetermined size to obtain a ceramic green sheet. Then, a predetermined number of the ceramic green sheets are laminated and pressure-bonded, and then cut into predetermined dimensions to obtain a ceramic molded body.

  Next, the ceramic molded body is subjected to binder removal treatment at 300 to 500 ° C. in an air atmosphere, and then subjected to a firing treatment at 1150 to 1250 ° C. in an air atmosphere, thereby producing an oxide ceramic.

  Thus, according to the present oxide ceramics, the main component is formed of a ferrite compound containing at least Sr, Co, and Fe, and Si is 0.01% in terms of the molar ratio x with respect to the main component. Mg is contained in a form in which part of the Fe is substituted, and the content of Mg in the main component is 0 in terms of a molar ratio y. Since it is 0.03 to 0.3, the temperature characteristic of the magnetic permeability can be improved without impairing the ferromagnetic dielectric characteristics such as insulation performance and electric polarization.

  Next, a ceramic electronic component using the present oxide ceramic will be described in detail.

  FIG. 1 is a front view showing an embodiment of a variable inductor as a ceramic electronic component according to the present invention, and FIG. 2 is a sectional view thereof.

  The variable inductor includes a component body 1 made of the oxide ceramic and external electrodes 2 a and 2 b formed at both ends of the component body 1.

  The variable inductor is provided with a coil so that magnetic flux passes through the component body 1 when a high-frequency signal flows. Specifically, in this embodiment, the coil 4 formed of a conductive material such as Cu is wound so as to suspend the external electrode 2a and the external electrode 2b.

  Furthermore, internal electrodes 3a to 3c are embedded in the component body 1 in parallel. Of these internal electrodes 3a-3c, the internal electrodes 3a, 3c are electrically connected to one external electrode 2a, and the internal electrode 3b is connected to the other external electrode 2b. This ceramic electronic component can acquire capacitance between the internal electrode 3a and the internal electrode 3b and between the internal electrode 3b and the internal electrode 3c.

  In addition, as an electrode material which forms external electrode 2a, 2b and internal electrode 3a-3c, if it has good electroconductivity, it will not specifically limit, Various types, such as Pd, Pt, Ag, Ni, Cu, etc. Metal materials can be used.

  In the variable inductor thus configured, the component body 1 is formed of the above-described oxide ceramics made of a ferromagnetic dielectric, and the coil 4 is wound so as to suspend the external electrode 2a and the external electrode 2b. Therefore, when a high frequency signal is input to the coil 4, the magnetic flux generated in the direction of arrow A passes through the component element body 1, and the number of turns of the coil, the element shape, and the permeability of the component element body 1 are changed. A corresponding inductance is obtained. In addition, when an electric field (voltage) is applied to the external electrodes 2a and 2b, a change in magnetization (change in permeability) occurs due to the electromagnetic effect, and the inductance L of the coil can be changed. Then, the change rate ΔL of the inductance L can be controlled by changing the electric field (voltage).

  And since the component body 1 is formed of the above-described oxide ceramics of the present invention, fluctuations in magnetic permeability can be suppressed even if the ambient temperature changes, so that the insulation performance and the electromagnetic effect are not impaired. In addition, a variable inductor having excellent permeability temperature characteristics and excellent reliability can be obtained.

  The variable inductor can be manufactured as follows.

  First, a ceramic green sheet is produced by the same method and procedure as the above oxide ceramic production method.

  Next, a conductive paste for internal electrodes whose main component is a conductive material such as Pd is prepared. Then, a conductive paste for internal electrodes is applied to the ceramic green sheet, and a conductive layer having a predetermined pattern is formed on the surface of the ceramic green sheet.

  Thereafter, the ceramic green sheet on which the conductive layer is formed and the ceramic green sheet on which the conductive film is not formed are laminated in a predetermined order, and then cut into predetermined dimensions to obtain a ceramic molded body.

  Next, the ceramic molded body is subjected to a binder removal treatment at 300 to 500 ° C. in an air atmosphere, followed by firing treatment at 1150 to 1250 ° C. in an air atmosphere, and then heat treatment in an oxygen atmosphere to obtain component parts. The body 1 is produced.

  Next, a conductive paste for external electrodes containing Ag or the like as a main component is applied to both ends of the component element body 1 and subjected to a baking process, followed by a polarization process, thereby producing a variable inductor.

  The polarization treatment is preferably performed in a magnetic field from the viewpoint of obtaining a larger electromagnetic effect, and the case where the polarization treatment is performed in a magnetic field will be described below.

  First, magnetic field polarization is performed by applying a magnetic field of 1T or more, and then an electric field of about 0.5 to 2 kV / mm is applied in a direction orthogonal to the direction of the magnetic field in a state where this magnetic field is applied. In the applied state, the magnitude of the magnetic field is gradually lowered to 0.1 to 0.5 T, thereby performing electric polarization. Then, by performing polarization treatment in a magnetic field in this way, a larger electromagnetic effect can be obtained.

  In the above embodiment, the internal electrodes are provided. However, when the internal electrodes are not provided, surface electrodes made of Pt, Ag, or the like are formed on both main surfaces of the component element body 1 to perform polarization treatment.

  As described above, in this embodiment, by applying an electric field, the magnetization (permeability) can be changed, and thereby the inductance L of the coil can be changed. In addition, by adjusting the applied electric field, it is possible to control the rate of change of the inductance L, and it is possible to obtain a variable inductor with good magnetic temperature characteristics and excellent reliability.

  The present invention is not limited to the above embodiment. For example, although the general formula (A) is given as an example of the present oxide ceramics, it is sufficient if it contains at least Sr, Co, Fe, Si, and Mg. For example, a part of Sr may be replaced with Ba. And additives such as Zr may be contained. Further, the molar ratio of Sr, Co, and Fe is allowed in a range that does not affect the characteristics even if a slight compositional deviation occurs.

  Moreover, the ceramic electronic component of the present invention can be used as a power generation element in addition to the variable inductor described above.

  That is, in this ceramic electronic component, a ferroelectric phase appears by applying a magnetic field and a ferroelectric phase appears, and a displacement current of an electromagnetic current flows when the magnetic field disappears due to no application of the magnetic field. Therefore, in an alternating magnetic field in which the appearance and disappearance of the ferromagnetic phase are repeated, the ceramic electronic component continues to discharge electric charges (electromagnetic current), and thus can be used as a power generation element in the same manner as an electromagnetic induction element. Become. Moreover, since the larger the electric polarization P, the larger the energy that can be obtained, good power generation characteristics can be obtained within the composition range of the present invention.

  Also, for example, by sticking the ceramic electronic component on a flexible stainless steel substrate or the like, vibrating the substrate in a magnetic field, and changing the magnitude of the magnetic field applied to the ceramic electronic component Since a desired power generation action can be obtained, the same use as a power generation element using a piezoelectric body is possible.

  That is, in a power generation element using a piezoelectric body, the piezoelectric body itself is vibrated and distorted, and therefore, when a large force is applied, the piezoelectric body itself may be damaged.

  On the other hand, in this ceramic electronic component, it is not necessary to distort the component body itself, and it is possible to realize a power generating element with excellent durability.

  Further, the ceramic electronic component can be used for a magnetic sensor that outputs a current according to the magnitude of the magnetic field and a current sensor that outputs a current according to the magnitude of the magnetic field formed by the current flowing through the coil.

  In the above embodiment, the electric polarization is performed in the direction perpendicular to the magnetic field direction in the magnetic field. However, when the crystal particles are polycrystalline, the magnetic field direction and the electric polarization direction are the same direction. Can also obtain a large electromagnetic effect.

  In addition, a large electromagnetic effect can be obtained even when the magnetic field is not applied after the magnetic field polarization and the electric polarization is performed, and can be appropriately selected according to the use form, environment, and the like.

  Next, examples of the present invention will be specifically described.

[Sample preparation]
Fe ₂ O ₃ , SrCO ₃ , Co ₃ O ₄ , MgCO ₃ , and SiO ₂ were prepared as ceramic raw materials.

Subsequently, in the general formula [Sr ₃ Co ₂ Fe _24-y Mg _y O ₄₁ —xSiO ₂ ], the ceramic raw materials were weighed so that x and y had a molar ratio shown in Table 1 after firing.

  Next, the ceramic raw material weighed in this way is put into a polyethylene pot mill together with PSZ balls, a water-based polymer dispersant (manufactured by Kao Corporation, Kaosela 2210) and pure water, and mixed and ground for 16 hours. Obtained.

  Next, the mixture was dried and sized, and then calcined at a temperature of 1100 ° C. for 4 hours in an air atmosphere to obtain a calcined product.

  Separately, polyvinyl butyral binder resin (manufactured by Sekisui Chemical Co., Ltd., ESREC B “BM-2”) was dissolved in a mixed solvent of ethanol and toluene, and a plasticizer was added to prepare a binder solution.

  Then, after sizing the calcined product, PSZ balls, a solvent-based dispersant (manufactured by Kao Corporation, Kaosela 8000), and a mixed solvent of ethanol and toluene are put in a pot mill, mixed and ground for 24 hours, and then the binder The solution was added and mixed again for 12 hours, thereby obtaining a ceramic slurry.

  Next, the ceramic slurry thus prepared was formed into a sheet having a thickness of about 50 μm by using a doctor blade method, and cut into a predetermined size using a mold to obtain a ceramic green sheet. Then, a predetermined number of the ceramic green sheets were laminated and pressure-bonded at a pressure of 196 MPa to obtain two types of sheet molded products having a thickness of 0.6 mm or 1.2 mm.

  And about the sheet molded product whose thickness is 0.6 mm, it cut | disconnected in length: 12mm and width: 12mm, and was set as the sheet-like molded object.

  The sheet molded product having a thickness of 1.2 mm was punched into a ring-shaped molded body having an outer diameter of 20 mm and an inner diameter of 10 mm.

Next, the sheet-like molded body and the ring-shaped molded body were subjected to a binder removal treatment at 500 ° C. in an air atmosphere, and then subjected to a firing treatment at 1190 ° C. in an air atmosphere for 18 hours. Further, in an oxygen atmosphere, 1150 ° C. Heat treatment was performed at a temperature of 10 hours, thereby producing a sheet-like sintered body and a ring-like sintered body.
The sintered body dimensions after firing are as follows: the sheet-like sintered body has a length of 10 mm, a width of 10 mm, and a thickness of 0.5 mm, and the ring-shaped sintered body has an outer diameter of 16.4 mm and an inner diameter of 8 mm. 0.1 mm, thickness: 1.0 mm.

  And about a ring-shaped sintered compact, Cu wire was wound around the thick part 40 times, the coil was formed, and each sample of sample numbers 1-21 for magnetic permeability measurement was obtained by this.

  Further, for the sheet-like sintered body, DC sputtering was performed using Pt as a target material, and surface electrodes having a thickness of about 300 nm were produced on both main surfaces of the sheet-like sintered body, and a sample number for measuring the electromagnetic characteristics Each sample of 1-21 was obtained. DC sputtering was performed by supplying Ar gas into a vacuum vessel adjusted to 5 mmT and supplying power of 150 W.

  The samples Nos. 1 to 21 were subjected to composition analysis using inductively coupled plasma emission spectroscopy (ICP) and fluorescent X-ray analysis (XRF), and each sample had the composition shown in Table 1. Further, when the crystal structure of each sample was examined by the X-ray diffraction (XRD) method, it was confirmed that the main component had a hexagonal Z-type crystal structure.

  Next, each sample for measuring the electromagnetic characteristics was subjected to polarization treatment.

  FIG. 3 is a perspective view schematically showing the polarization processing apparatus.

  In this polarization processing apparatus, signal lines 24 a and 24 b are connected to a sample 23 in which surface electrodes 22 a and 22 b are formed on both main surfaces of a component element body 21, and a direct current is connected between the signal line 24 a and the signal line 24 b. A power supply 25 is interposed.

  The sample 23 has an internal electrode as described above, the direction of the magnetic field applied to the sample 23 (indicated by arrow B) and the direction of the electric field in which electric polarization is performed (indicated by arrow C). Are arranged so as to be orthogonal to each other.

  First, using an electromagnet (not shown), a 1.5 T DC magnetic field was applied for 1 minute at room temperature, and magnetic field polarization was performed in the direction of arrow B. Next, while applying an electric field of 800 V / mm between the surface electrodes 22a and 22b, the magnitude of the magnetic field is gradually reduced from 1.5T to 0.5T, and the direction of arrow C is 3 minutes in the magnetic field of 0.5T. Electric polarization was performed. By performing the polarization process in the magnetic field in this way, it is possible to obtain a larger electromagnetic effect.

  Next, the electric field and the magnetic field were not applied, and the evaluation sample was left for about 1 hour. In this way, after performing the polarization treatment, it is possible to obtain a larger electromagnetism effect by leaving it for a predetermined time.

(Sample evaluation)
(Measurement of electric polarization P and specific resistance ρ)
For each sample for measuring the electromagnetic characteristics, the electromagnetic current was measured, and the electric polarization P was obtained from the electromagnetic current.

  FIG. 4 is a perspective view schematically showing an electromagnetic current measuring apparatus for the sample 23.

  This characteristic evaluation apparatus is provided with a pier-conmeter (made by Keithley Instruments, Inc., 6487) 26 in place of the DC power supply 25 in FIG. 3, and the evaluation sample is the direction of the applied magnetic field as in FIG. And the direction of the electric field at the time of electric polarization are orthogonal to each other.

  And while controlling to a temperature of 25 ° C. with a low-temperature cryostat (manufactured by Toyo Technica Co., Ltd., LN-Z type), using an electromagnet, a plurality of magnetic fields in the range of 0 to 0.21 T at a rate of 1.7 T / min The electric charge discharged from the sample at that time, that is, the electromagnetic current, was measured with the pier-conmeter 26.

  Next, the current density J of this electromagnetic current was integrated over time, and the electric polarization P serving as a ferroelectric index was obtained.

  That is, the current density J of the electromagnetic current can be expressed by Equation (3).

J = dP / dt (3)
Therefore, the electric polarization P can be obtained by integrating the current density J of the electromagnetic current with time t.

  Here, the reason why the electric polarization P becomes an index of the ferromagnetic dielectric property will be described.

  As an index of the ferromagnetic dielectric property, an electromagnetic coupling coefficient α defined by the equation (4) is known.

α = μ ₀ (dP / dB) (4)
Here, μ ₀ is the vacuum permeability (= 4π × 10 ⁻⁷ H / m).

  Therefore, the change of the electric polarization P with respect to the change of the magnetic field B (T) is expressed by Equation (5).

dP / dB = (dP / dt) / (dB / dt) = J / (dB / dt) (5)
Here, dB / dt indicates the magnetic field sweep rate.

  When the above equation (4) is substituted into the equation (5), the electromagnetic coupling coefficient α can be expressed by the equation (6).

α = (μ ₀ · J) / (dB / dt) (6)
Therefore, the electromagnetic coupling coefficient α can be obtained by dividing the product of the vacuum permeability μ ₀ and the current density J by the magnetic field sweep rate (dB / dt).

  As is clear from Equation (6), the electromagnetic coupling coefficient α increases as the current density J of the electromagnetic current increases. Therefore, the larger the electric polarization P from Equation (3), the greater the electromagnetism effect. And a desired ferromagnetic dielectric can be obtained.

  FIG. 5 is a graph showing the current density and electric polarization characteristics of Sample No. 16.

The horizontal axis is time t (sec), the right vertical axis is the electric polarization P (μC / m ² ), and the left vertical axis is the current density J (μA / m ² ).

As apparent from FIG. 5, in the sample No. 16, the current density J is as large as 3.5μA / ^{m 2,} electric polarization P is obtained a large value 12.3μC / ^{m 2} and 10 [mu] C / ^{m 2} or more It can be seen that the characteristics as a ferromagnetic dielectric are expressed.

  For sample numbers 1 to 15 and 17 to 21 as well, the electric current was measured and the electric polarization P was obtained in the same manner as described above. This electric polarization P was not only the ceramic composition but also magnetic field polarization and electric field polarization. Therefore, all samples were subjected to polarization treatment under the same conditions.

  Next, with respect to each sample of sample numbers 1 to 21, an electrometer (manufactured by ADMT, 8252) was used, and the specific resistance ρ was determined by the two-terminal method.

(Measurement of permeability)
BH curves (magnetic hysteresis curves) at 10 ° C., 20 ° C., 25 ° C., 30 ° C. and 35 ° C. are obtained using a BH analyzer (SYW-232, SY-301, manufactured by Iwatatsu Keiki Co., Ltd.). It was.

  FIG. 6 shows a BH curve of sample number 16 when the magnitude of the magnetic field is varied in the range of 0 to 4000 A / m. In the figure, the horizontal axis represents the magnetic field H (A / m), and the vertical axis represents the magnetic flux density B (mT).

  And the magnetic permeability (= B / H) in each magnetic field was calculated | required from the BH curve, and the magnetic permeability change rate (DELTA) micromicrometer in + 10 + 35 degreeC on the basis of temperature 25 degreeC was calculated | required based on Numerical formula (7).

Δμ = {(μ2−μ3) / μ1} × 100 (7)
Here, μ1 is a magnetic permeability at a temperature of 25 ° C., μ2 is a magnetic permeability at a temperature of 35 ° C., and μ3 is a magnetic permeability at a temperature of 10 ° C.

  Table 1 shows the component composition, specific resistance ρ, electric polarization P, and permeability change rate Δμ in a magnetic field of 1000 A / m for each of sample numbers 1 to 21.

The electrical polarization P was 10 μC / m ² or more, the specific resistance ρ was 100 MΩ · cm or more, and the permeability change rate Δμ was determined to be 35% or less, and the others were determined to be defective.

  Sample No. 1 has good resistivity ρ and electric polarization P, but the oxide ceramic contains neither Si nor Mg. Therefore, the permeability change rate Δμ is as large as 56.5%, and the permeability μ It was found that the temperature characteristics were inferior.

Sample No. 2 contains SiO ₂ but has a small molar ratio x of 0.01, so that the permeability change rate Δμ is as large as 55.1%, and the temperature characteristic of the permeability μ is the same as Sample No. 1. It turned out to be inferior.

Sample Nos. 3 to 5 differ in the SiO ₂ molar ratio x in the range of 0.04 to 0.237, but do not contain Mg, and therefore the content of SiO ₂ increases. As a result, it was found that the specific resistance ρ decreased and the insulation performance was inferior. This is considered that tetravalent Si existing in the crystal grain boundary is slightly dissolved in the Fe site to generate conduction electrons. Therefore, in these sample numbers 3 to 5, the specific resistance ρ was 100 MΩ · cm or less, and the magnetic polarization and the electric field polarization could not be performed. Therefore, the electric polarization P could not be measured.

Sample Nos. 9 and 13 contain SiO ₂ molar ratio x in excess of 0.237, and Mg molar ratio y is as small as 0.03 or 0.1. Therefore, specific resistance ρ is 100 MΩ. -It fell to below cm, therefore, like sample numbers 3-5, magnetic field polarization and electric field polarization could not be performed, and electric polarization P could not be measured.

Sample No. 17 contains SiO ₂ molar ratio x in excess of 0.237, and Mg molar ratio y is 0.3, which is within the scope of the present invention. P was as low as 3.5 μC / m ² . That is, since the molar ratio x of SiO ₂ is excessively contained at 0.237, the amount of segregation to the crystal grain boundary of SiO ₂ is increased and Mg is also relatively contained. It is considered that Mg also segregates at the grain boundary beyond the solid solution limit at the Fe site. Therefore, a compound is formed between Mg and Si and a segregation phase is generated. Therefore, although the specific resistance is large, the applied electric field is concentrated on the segregation phase at the grain boundary when electric polarization is performed. It is considered that the electric polarization P was lowered without being applied to the particles.

  In Sample Nos. 18 to 21, since the molar ratio y of Mg was excessively contained at 0.4, the electric polarization P was low, and a sufficient electromagnetism effect could not be obtained.

On the other hand, sample numbers 6-8, 10-12, and 14-16 have a molar ratio x of 0.01-0.2 and a molar ratio y of 0.03-0.3, all within the scope of the present invention. Therefore, the specific resistance ρ can be 100 MΩ · cm or more to ensure good insulation performance, and the electric polarization P can be 10 μC / m ² or more to obtain a good electromagnetism effect. It has been found that the magnetic permeability change Δμ can be suppressed to 35% or less, and therefore, even if the temperature changes, the fluctuation of the magnetic permeability is small, and an oxide ceramic having good temperature characteristics can be obtained.

  FIG. 7 is a diagram showing the relationship between the magnetic field H and permeability change rate Δμ of sample number 16 which is a sample of the present invention, and FIG. 8 is the magnetic field H and permeability change of sample number 1 which is a sample outside the scope of the present invention. It is a figure which shows the relationship with rate (DELTA) micro.

  7 and 8, the horizontal axis represents the magnetic field H (A / m), and the vertical axis represents the permeability change rate Δμ.

  As can be seen from FIG. 8, Sample No. 1 outside the scope of the present invention has the largest fluctuation width when the magnetic field H is 1000 A / m. In this case, the magnetic permeability increases by 30% at 35 ° C., decreases by 26.5% at 10 ° C., and varies by 56.5% in the range of + 10 ° C. to + 35 ° C. I understand.

  On the other hand, as shown in FIG. 7, sample No. 16 within the scope of the present invention has a magnetic permeability H of 1000 A / m, and the magnetic permeability is only + 15% increase at 35 ° C. with respect to 25 ° C. It was found that the decrease was only 14.1% at 10 ° C and could be suppressed to 29.1% in the range of + 10 ° C to + 35 ° C. In Sample No. 16, the magnetic field H is about 1200 A / m and the magnetic permeability change rate Δμ has the largest fluctuation range. Even in this case, the magnetic permeability is 35 on the basis of 25 ° C. It was found that it was only + 14% increase at 10 ° C, 21% decrease at 10 ° C, and 35% in the range of + 10 ° C to + 35 ° C.

Fe ₂ O ₃ , SrCO ₃ , Co ₃ O ₄ , MgCO ₃ , SiO ₂ , and BaCO ₃ were prepared as ceramic raw materials.

  And the sample of sample numbers 31-33 was produced with the method and procedure similar to Example 1 except having weighed the ceramic raw material so that the composition after baking might become Table 2. FIG.

  In addition, the composition analysis of each sample of the sample numbers 31-33 was performed using ICP method and XRF method like Example 1, and the crystal structure was confirmed by XRD method.

  Next, the electric polarization P, the specific resistance ρ, and the permeability change rate Δμ were measured for each of the samples Nos. 31 to 33 in the same manner and procedure as in Example 1.

  Table 2 shows the composition components of each sample and the measurement results.

As apparent from the sample numbers 31 to 33, even if a part of Sr is replaced with Ba, or even if the molar content of Sr or Fe slightly deviates from the stoichiometric ratio, the molar ratio of SiO ₂ x Is 0.01 ≦ x ≦ 0.2 and the molar ratio y of Mg is 0.03 ≦ y ≦ 0.3 and within the range of the present invention, the specific resistance ρ is 100 MΩ · cm or more and the electric polarization P is 10 μC. / m ² or more, and the size of the magnetic field can be suppressed the permeability rate of change Δμ below 35% 1000A / m was confirmed.

  Without impairing the insulation performance and the ferromagnetic dielectric properties, it is possible to realize oxide ceramics with improved permeability temperature characteristics and ceramic electronic components such as variable inductors using the oxide ceramics.

1 Component element body 2a, 2b External electrode 3a-3c Internal electrode

Claims (6)

The main component is formed of a ferrite compound containing at least Sr, Co, and Fe,
Si is contained in the range of 0.01 to 0.2 in terms of molar ratio x with respect to the main component,
Mg is contained in a form in which a part of Fe is substituted, and the content of Mg in the main component is 0.03 to 0.3 in terms of molar ratio y, Oxide ceramics. It is represented by the general formula [Sr ₃ Co ₂ Fe _24-y Mg _y O ₄₁ —xSiO ₂ ] (where 0.01 ≦ x ≦ 0.2, 0.03 ≦ y ≦ 0.3). The oxide ceramic according to claim 1.   3. The oxide ceramic according to claim 1, wherein a part of the Sr is substituted with Ba. A ceramic electronic component in which external electrodes are formed on the surface of a component body,
A ceramic electronic component, wherein the component element body is formed of the oxide ceramic according to any one of claims 1 to 3.   The ceramic electronic component according to claim 4, wherein the coil is arranged so as to have an inductance corresponding to a magnetic permeability of the component element body.   6. The ceramic electronic component according to claim 4, wherein an internal electrode is embedded in the component element body.

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