JP6103379B2 - 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, a ferromagnetic dielectric (multiferroics) material that exhibits a combined action in which ferromagnetism and ferroelectricity coexist has attracted attention and has been actively researched and developed.

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

  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. Application to various magnetic electronic devices such as a variable magnetization device for a write head, a magnetic sensor for detecting magnetism, and a nonvolatile memory is expected.

  For example, Patent Document 1 discloses that the spin is rotating so that the ferroelectricity and the spin direction are along the outside of a cone (the opening angle α of the apex of the cone is in the range of 0 ° <α ≦ 90 °). A multiferroic element has been proposed in which an external magnetic field is applied to a multiferroic solid material having ferromagnetism having a structure to control the direction of electric polarization substantially perpendicular to the external magnetic field.

In this Patent Document 1, by using CoCr ₂ O ₄ (M = Mn, Fe, Co, Ni) as a ferromagnetic dielectric material (multiferroic material), it is caused by the action of a magnetic field in a cryogenic region near 26K. Electric polarization can be generated, and an electric polarization of ² μC / m ² is obtained in the vicinity of 5K.

  Patent Document 2 discloses a multiferroic element which is a multiferroic solid material having both ferroelectricity and ferromagnetism containing iron oxide as a main raw material and in which a current is induced by a weak external magnetic field of 300 gauss or less. Has been proposed.

In Patent Document 2, when a ferrite compound of Ba ₂ Mg ₂ Fe ₁₂ O ₂₂ is used as a ferromagnetic dielectric material and a low magnetic field of 300 G (0.03 T) is applied, −268 ° C. (5 K). It is described that a current flows in accordance with the application of an alternating magnetic field, and the electric polarization alternately generates positive and negative.

International Publication No. 2007/135817 (Claims 1 and 3, paragraph number [0031], FIG. 7 etc.) JP 2009-224563 (Claims 1 and 3, paragraph number [0032], FIG. 7 etc.)

  By the way, in order to apply a ferromagnetic dielectric material to various electronic components such as a variable inductor and a nonvolatile memory, it is necessary to develop an electromagnetic effect at room temperature.

  However, in the above Patent Documents 1 and 2, since the electromagnetism effect is manifested only at a low temperature range far below room temperature and cannot be manifested at room temperature, various ceramic electronic components utilizing the electromagnetism effect are practically used. The situation has not been realized yet.

  The present invention has been made in view of such circumstances, and provides oxide ceramics that can exhibit a desired electromagnetic effect at room temperature and a low magnetic field, and ceramic electronic components using the oxide ceramics. For the purpose.

Oxide ceramics having a hexagonal Y-type crystal structure represented by the general formula A ₂ M ₂ Fe ₁₂ O ₂₂ (A is Ba, Sr, M is Co, Zn) are capable of generating and controlling electric polarization in a low magnetic field. In addition, the helical magnetic order capable of developing ferroelectricity can be stably maintained up to a relatively high temperature. Therefore, it is considered possible to develop an electromagnetic effect at room temperature by making improvements. It is done.

  From these viewpoints, the present inventors have repeated trial and error with respect to oxide ceramics mainly composed of a hexagonal Y-type crystal structure, and have conducted intensive research. As a result, the mixing ratio of Ba and Sr was adjusted to a predetermined range. On the other hand, by including Al within a predetermined range in a form that replaces a part of Fe, and by including Zr within a predetermined range without depending on the existing form, the insulation can be greatly improved. The inventors have found that a ferromagnetic dielectric capable of inducing electric polarization at room temperature and a low magnetic field can be obtained.

  The present invention has been made based on such knowledge, and the oxide ceramic according to the present invention has a hexagonal Y-type crystal structure containing at least Sr, Ba, Co, Zn, and Fe as main components. In addition, n moles of Zr are contained with respect to 1 mole of the main component, and the Ba content is represented by a mole ratio of the Ba content to the total amount of Sr and Ba (Ba / (Sr + Ba)) x / 2. When x is 0.9 to 1.1, it is contained in the form of replacing a part of the Sr, and at least Al, the Al content is the total amount of Al and Fe, Fe deficiency The part of the Fe contained in the Fe site is substituted so that y is in the range of 0.8 to 1.2 when the content molar ratio to Al (y / 12 in terms of Al / (Al + Fe + Fe deficiency)) And is contained in the form of When the amount of deficiency with respect to the stoichiometric composition of e-site is z / 12 in terms of molar ratio, (n, z) is A (0.05, 0.05), B (0.1, 0.05), C (0.4, 0.35), D (0.4, 0.4), E (0.2, 0.4), F (0.05, 0.1) It is characterized by being in

The oxide ceramics of the present invention have the general formula _{[Sr 2-x Ba x CoZnFe} 12-yz Al y O 22 + nZrO 2] ( although, 0.9 ≦ x ≦ 1.1,0.8 ≦ y ≦ 1 .2) is preferred.

  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 has a hexagonal Y-type crystal structure containing at least Sr, Ba, Co, Zn, and Fe, and n mol of Zr is contained per mol of the main component. The Ba is contained in a form in which a part of the Sr is substituted so that x is 0.9 to 1.1 when the content of the Ba is x / 2. At least Al, when the content of Al is y / 12 in terms of molar ratio, a part of the Fe contained in the Fe site is such that y is in the range of 0.8 to 1.2. (N, z) is represented by A (0.05,0) on the coordinate axis when the defect amount with respect to the stoichiometric composition of the Fe site is z / 12 in terms of molar ratio. .05), B (0.1, 0.05), C (0.4, 0.35), D (0.4 0.4), E (0.2, 0.4), and F (0.05, 0.1), so that the insulation can be greatly improved, and the room temperature is low. A ferromagnetic material capable of producing a large electromagnetic effect with a magnetic field and capable of generating a desired electric polarization can be obtained.

  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 realize various ceramic electronic components such as a variable inductor having a good insulating property and exhibiting a large electromagnetic effect at room temperature and a low magnetic field.

  Furthermore, the oxide ceramic of the present invention has a feature that the electric polarization is reversed by a magnetic field, and due to its nature, the electromagnetic coupling coefficient α has a maximum value in the vicinity of the zero magnetic field and does not require a bias magnetic field or a small bias. A large electromagnetic effect can be obtained by the magnetic field.

It is a diagram showing a relationship between defective molar ratio z of oxide ceramics molar ratio n and the Fe site of ZrO ₂ of the present invention. 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. In Example 1, a diagram illustrating a relationship between the molar ratio n and the specific resistance ρ of ZrO _2. It is the perspective view which showed typically the example of 1 structure of the physical characteristic evaluation apparatus used in Example 1. FIG. It is the perspective view which showed typically the other structural example of the special characteristic evaluation apparatus used in Example 1. FIG. In Example 1, a diagram plotting the relationship between the defect molar ratio z of molar ratio n and the Fe site of ZrO _2. FIG. 6 is a diagram showing a current density characteristic of Sample No. 19 in Example 1. 6 is a diagram showing the electric polarization characteristics of sample number 19 in Example 1. FIG.

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

  The oxide ceramic according to an embodiment of the present invention has a hexagonal Y-type crystal structure containing at least Sr, Ba, Co, Zn, and Fe as a main component, and n per mol of the main component. Mole Zr is contained, and when the Ba content is expressed as a molar ratio (Ba / (Sr + Ba)) x / 2 with respect to the total amount of Sr and Ba, x is 0.9 to 1.1. So that a part of the Sr is substituted and at least Al, the Al content is the molar ratio of Al to Fe and the total amount of Fe deficiency (Al / (Al + Fe + Fe deficiency)). When converted to y / 12, y is contained in a form that substitutes part of the Fe contained in the Fe site so that y is in the range of 0.8 to 1.2.

  And when the amount of defects with respect to the stoichiometric composition of Fe sites is z / 12 in terms of molar ratio, (n, z) is within the range of the region X surrounded by the points A to F shown in FIG. Has been.

  Here, each point (n, z) of the points A to F shows the following values.

A (0.05, 0.05), B (0.1, 0.05), C (0.4, 0.35), D (0.4, 0.4), E (0.2, 0.4), F (0.05, 0.1)
That is, this oxide ceramic is mainly composed of a SrBaCoZnFe ₁₂ O ₂₂ {(Sr, Ba) O _2. (Co, Zn) O _2. (Fe ₂ O ₃ ) ₆ } -based compound having a hexagonal Y-type crystal structure. And can be represented by the following general formula (A).

_{Sr 2-x Ba x CoZnFe 12} -y-z Al y O 22 + nZrO 2 ... (A)

Here, the molar ratio of Ba to the total amount of Sr and Ba in the (Sr, Ba) site (hereinafter referred to as “Ba substitution molar ratio”) x / 2, and Fe, Al and defects in the Fe site The content molar ratio of Al with respect to the total amount of the molar ratio z (hereinafter referred to as “Al substitution molar ratio”) y / 12 satisfies Expressions (1) and (2). The relationship between the molar ratio n of ZrO _{2 to} 1 mol of the main component and the defect molar ratio z from the stoichiometric composition of the Fe site is (n, z). It is blended to become.

0.9 ≦ x ≦ 1.1 (1)
0.8 ≦ y ≦ 1.2 (2)

  As described above, the present oxide ceramics has good insulation because the general formula (A) satisfies the formulas (1) and (2) and (n, z) is in the region X of FIG. Large electric polarization can be obtained at room temperature and a low magnetic field, and a desired electromagnetic effect can be exhibited.

That is, the present inventors conducted extensive research using a ferrite compound having a hexagonal Y-type crystal structure mainly composed of SrBaCoZnFe ₁₂ O ₂₂ , and found that the substitution molar ratio x of Ba and x of Al By blending y having a substitution molar ratio y / 12 within the predetermined range shown by the mathematical formulas (1) and (2), and further containing Zr so as to be within the predetermined range with respect to 1 mol of the main component, It has been found that the insulation can be dramatically improved, and thereby, it is possible to obtain a ferromagnetic dielectric capable of inducing electric polarization at room temperature and a low magnetic field and exhibiting an electromagnetic effect at room temperature and a low magnetic field.

In this case, Zr is mainly such that the relationship between the content molar ratio n of ZrO ₂ and the defect molar ratio z / 12 (the defect molar amount of Fe with respect to the main component 1) z is in the region X of FIG. The component may be contained with respect to 1 mol of the component, for example, Zr in an amount corresponding to z having a defect molar ratio z / 12 may be included, or Zr exceeding z having a defect molar ratio z / 12 may be included. Also good. Further, Zr lower than z having a defect molar ratio z / 12 of Fe sites may be included so that a defect portion is formed in the crystal lattice.

  As a result, the insulating property is remarkably improved. The reason is considered as follows.

  That is, in the region X of FIG. 1, Zr contained at a ratio of n mole to 1 mole of the main component is partly dissolved in the main component, but most of the Zr is segregated at the grain boundary and is different in phase. It is considered that a dramatic improvement in the insulating property has been made possible by forming such a heterogeneous phase and segregating such a different phase at the crystal grain boundary. However, since the voltage is not applied to the crystal grains even if only the crystal grain boundary becomes high resistance, the resistance in the crystal grains is also high resistance by introducing some Fe deficiency in addition to the addition of Zr. Inferred.

  In addition, when the molar ratio n of z and Zr of the defect molar ratio z / 12 is outside the range of the region X, the insulating property is improved, but there is a possibility that the electromagnetic effect cannot be exhibited, or the insulating property is insufficient. There is a risk that the electromagnetic effect cannot be exhibited. For example, when z of the defect molar ratio z / 12 of Fe site exceeds 0.4, there is a possibility that although the insulating property is improved, the electromagnetic effect cannot be exhibited. This is because, as described above, Zr contained in the main component is considered to be mostly segregated at the crystal grain boundaries, so that the Fe site defects increase and the balance is lost, thus inducing electrical polarization. It seems to be difficult to form such a helical magnetic order. In addition, even if the molar ratio n of Zr is large, if the z of the defect molar ratio z / 12 of Fe site is reduced, the insulation is insufficient, and it is difficult to exhibit a desired electromagnetic effect at room temperature and in a low magnetic field. There is a risk.

  Further, the reason why x of the substitution molar ratio x / 2 of Ba is set in the range of 0.9 to 1.1 as shown in the above formula (1) is as follows.

  That is, when x of the substitution molar ratio x / 2 of Ba is less than 0.9 or more than 1.1, insulation can be sufficiently ensured, but it becomes difficult to induce a helical magnetic order at room temperature. There is a risk that polarization cannot be generated.

  Further, the reason why the substitution molar ratio y / 12 of y is set to the range of 0.8 to 1.2 as shown in the above formula (2) is as follows.

  That is, when y of Al substitution molar ratio y / 12 is less than 0.8, as in the case of x of Ba substitution molar ratio x / 2, the insulating property can be sufficiently ensured, but at room temperature, it is helical. It becomes difficult to induce the magnetic order, and there is a possibility that the electric polarization Pr cannot be generated.

  On the other hand, if the substitution molar ratio y / 12 of y exceeds 1.2, in this case as well, although insulation can be sufficiently ensured, different phases other than the hexagonal Y-type crystal phase not involving Zr are likely to be generated. For this reason, such a heterogeneous phase inhibits the expression of the electromagnetic characteristics, and as a result, it becomes difficult to obtain electric polarization.

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

First, as a ceramic raw material, Fe compound such as Fe ₂ O ₃ , Sr compound such as SrCO ₃ , Ba compound such as BaCO ₃ , Zn compound such as ZnO, Co compound such as Co ₃ O ₄ , Al ₂ O _3, etc. And a Zr compound such as ZrO ₂ are prepared.

Next, in the composition after firing, the general formula (A) satisfies the mathematical formulas (1) and (2), and the ZrO ₂ content molar ratio n and the Fe site defect molar ratio z / 12 z are: Each ceramic raw material is weighed so as to satisfy the region X in FIG. 1 while considering that chemical components in the grinding medium described later are mixed in the sintered ceramic body after firing.

  That is, oxide ceramics are generally produced by putting a ceramic raw material into a pulverizer together with a pulverizing medium, a solvent, and other additives, and firing through a mixed pulverization process. And also in this Embodiment, the said oxide ceramics are produced through such a process.

  As the grinding medium, a partially stabilized zirconium (hereinafter referred to as “PSZ”) ball or a stainless steel (SUS304) steel ball is usually used.

Among these grinding media, PSZ balls, the ZrO ₂ was added a stabilizer such as _Y 2 _{O 3,} thereby stabilizing the crystal structure of ZrO _2. Therefore, since ZrO ₂ is contained in the PSZ ball, ZrO ₂ in the PSZ ball may be mixed into the oxide ceramics by the mixing and pulverizing process in the pulverizer. Also, when steel balls are used, there is a possibility that the Fe content in the steel balls is mixed into the oxide ceramics.

On the other hand, the SrBaCoZnFe ₁₂ O _22- based hexagonal Y-type crystal structure is very complex, and even if a slight compositional deviation occurs, the fine structure changes, which may affect the ferromagnetic dielectric properties and insulation. There is.

Therefore, in the present embodiment, a predetermined amount of the ceramic raw material is weighed in consideration that the chemical components in the grinding medium are mixed into the oxide ceramic. Specifically, when PSZ balls are used as the grinding media, it is considered that ZrO ₂ from the PSZ balls is mixed into the oxide ceramics. When steel balls are used as the grinding media, oxide ceramics are used. Each ceramic raw material is weighed in consideration that the Fe content from the steel ball is mixed in.

  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 compact is subjected to a binder removal treatment at 300 to 500 ° C. in an air atmosphere, and then fired at 1150 to 1250 ° C. in an air atmosphere to obtain a ceramic sintered body.

  And after that, it heat-processes sufficiently in an atmospheric condition, and oxide ceramics are produced by this.

  Thus, according to the present oxide ceramics, it has a hexagonal Y-type crystal structure containing at least Sr, Ba, Co, Zn, and Fe, and the general formula (A) is expressed by the formulas (1) and (2). Satisfactory, and the Zr content molar ratio n and the Fe site defect molar ratio z / 12 z are within the range of the region X in FIG. 1, so that the insulation is greatly improved, and a low magnetic field can be applied even at room temperature. Electrical polarization can be generated, and an oxide ceramic having ferromagnetic dielectric properties can be obtained.

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

  FIG. 2 is a front view showing an embodiment of a variable inductor as a ceramic electronic component according to the present invention, and FIG. 3 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. Further, when a voltage (electric field) is applied to the external electrodes 2a and 2b, a change in magnetization 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 voltage.

  Since the component body 1 is formed of the above-described oxide ceramics of the present invention, the insulation is good, electric polarization can be obtained at room temperature and in a low magnetic field, and an electromagnetic effect can be exhibited. it can.

  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, this ceramic molded body is treated to remove the binder at 300 to 500 ° C. in an air atmosphere, and then fired at 1150 to 1250 ° C. in an air atmosphere to obtain a ceramic sintered body. Heat treatment is performed in an atmosphere to produce the component body 1.

  Next, a conductive paste for external electrodes mainly composed of Ag or the like is applied to both end portions of the component element body 1 and subjected to a baking treatment, and thereafter a polarization treatment is performed.

  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, thereby producing a variable inductor. Then, by performing polarization treatment in a magnetic field in this way, a larger electromagnetic effect can be obtained.

  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, the rate of change of the inductance L can be controlled, and it can be used as a variable inductor.

  The present invention is not limited to the above embodiment. Although the variable inductor has been described in the above embodiment, the oxide ceramic of the present invention exhibits a desired electromagnetic dielectric property by exhibiting a large electromagnetic effect at room temperature and a low magnetic field. It can also be applied to ceramic electronic components. That is, a magnetic sensor that outputs a current according to the magnitude of the magnetic field, a current sensor that outputs a current according to the magnitude of the magnetic field formed by the current flowing in the coil, a non-volatile memory that controls magnetization by an electric field, and a variable capacitor A device or the like can be realized.

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

  Further, even if the magnetic field is not applied after the magnetic field polarization and electric field polarization is performed, a large electro-magnetic effect can be obtained, and the magnetic field can be appropriately selected according to the usage form, environment, and the like.

  Moreover, in the said embodiment, although general formula (A) was mentioned as an example of this oxide ceramic, you may contain an additive in the range which does not deviate from the summary of this invention, and O (oxygen) As for the content molar ratio, a slight deviation from the stoichiometric ratio is allowed as long as it does not affect the characteristics.

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

Fe ₂ O ₃ , SrCO ₃ , BaCO ₃ , Co ₃ O ₄ , ZnO, Al ₂ O ₃ , and ZrO ₂ were prepared as ceramic raw materials.

Then, the Ba substitution molar ratio x / 2 x after firing, the Al substitution molar ratio y / 12 y, the Fe site defect molar ratio z / 12 z, and the moles of ZrO ₂ with respect to 1 mol of the main component The ceramic raw material was weighed so that the chemical component of the grinding medium was mixed into the oxide ceramic so that the ratio n would be the composition shown in Table 1.

That is, in this example, PSZ balls or steel balls made of stainless steel (SUS304) were used as a grinding medium in a mixing and grinding process in a grinding machine to be described later. As described in [Mode for Carrying Out the Invention] Furthermore, there is a possibility that ZrO ₂ is mixed from the PSZ ball into the oxide ceramic, and Fe is mixed from the steel ball.

  Therefore, in this example, the ceramic raw materials were weighed so that oxide ceramics having a desired composition were obtained after firing.

  Specifically, when the present inventors conducted a separate experiment, when PSZ balls were used as the grinding media, as a result of quantitative analysis, 0.35 wt% Zr component was mixed, and steel balls were used as the grinding media. As a result of composition analysis, it was found that 1.5 wt% Fe component was mixed when used.

Therefore, for sample numbers ₂ to 19 containing ZrO ₂ , the ceramic raw materials were weighed in consideration of ZrO ₂ mixed from the PSZ balls on the assumption that PSZ balls were used as the grinding media. For sample No. 1 containing no ZrO ₂ , each ceramic raw material was weighed in consideration of the Fe component mixed from the steel balls on the assumption that the steel balls were used as the grinding media.

  Next, the ceramic raw material weighed in this way is charged with an aqueous polymer dispersant (manufactured by Kao Corporation, Kaosela 2210) and pure water together with PSZ balls or steel balls into a polyethylene pot mill and mixed and pulverized for 16 hours. To obtain a mixture.

  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.

  Next, after sizing the calcined product, a solvent-based dispersant (manufactured by Kao Corporation, Kaosela 8000) and a mixed solvent of ethanol and toluene are put into a pot mill together with PSZ balls or steel balls, mixed and ground for 24 hours, The binder 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, pressure-bonded at a pressure of 196 MPa, and cut to prepare ceramic molded bodies of sample numbers 1 to 19 having a length: 12 mm, a width: 12 mm, and a thickness: 0.6 mm.

  Next, the ceramic compacts of Sample Nos. 1 to 19 were subjected to a binder removal treatment at 500 ° C. in an air atmosphere, and then subjected to a firing treatment at 1200 ° C. in an air atmosphere for 18 hours. A ceramic sintered body was produced.

  Next, the ceramic sintered bodies of sample numbers 1 to 19 were subjected to heat treatment at a temperature of 1090 ° C. for 10 hours in an oxygen atmosphere of 0.1 MPa (1 atm), thereby producing the component bodies of sample numbers 1 to 19 .

  The dimensions of the component body were length: 10 mm, width: 10 mm, and thickness: 0.5 mm.

  Next, for each of the component bodies of sample numbers 1 to 19, DC sputtering was performed using Pt as a target material on both main surfaces to produce a surface electrode having a thickness of about 300 nm. Got. DC sputtering was performed by supplying Ar gas into a vacuum vessel adjusted to 5 mmT and supplying power of 150 W.

  And about each sample of the sample numbers 1-19, when the composition analysis was carried out using the inductively coupled plasma emission spectroscopy (ICP) method and the fluorescent X ray analysis (XRF) method, each sample had the composition shown in Table 1. It was confirmed to have. Further, when the crystal structure of each sample was examined by an X-ray diffraction (XRD) method, it was confirmed that it had a hexagonal Y-type crystal structure.

(Sample evaluation)
(Insulation evaluation)
Among the above sample numbers 1 to 19, for each sample number 1 to 5 having the same molar ratio (n = z) of the defect amount z of Fe site and the content n of ZrO ₂ , a high resistance meter (US Keithley The specific resistance ρ was obtained using 6487) manufactured by Instrument.

FIG. 4 is a diagram showing the relationship between the molar ratio n of ZrO ₂ and the specific resistance ρ. The horizontal axis indicates the molar ratio n of ZrO ₂ and the vertical axis indicates the specific resistance ρ.

As can be seen from FIG. 4, Sample No. 1 does not contain ZrO ₂ , so the specific resistance ρ is as extremely low as 7.2 MΩ · cm, indicating that the sample is inferior in insulation.

  On the other hand, Sample Nos. 2 to 5 were found to have good insulating properties with a specific resistance ρ of 50 MΩ · cm or more.

From the above, it can be seen that by including ZrO ₂ in the main component having a hexagonal Y-type crystal structure, the insulation can be improved.

(Evaluation of electromagnetic effect)
Next, each sample of sample numbers 1 to 19 was subjected to polarization treatment.

  FIG. 5 is a perspective view schematically showing the polarization processing apparatus.

  That is, 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 body 21, and the signal lines 24 a and 24 b are connected between the signal lines 24 a and 24 b. A DC 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 field 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.

  Next, the electric current of each sample was measured, and the characteristics were evaluated.

  FIG. 6 is a perspective view schematically showing a characteristic evaluation 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 of FIG. 5, and the evaluation sample is the direction of the magnetic field to be applied, 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.

  Of the above samples, sample numbers 16, 17 and 19 were measured using a physical property measuring device (manufactured by Quantum Design, PPMS) in order to evaluate the behavior of the electromagnetic properties in more detail. The polarization treatment and the measurement of the electromagnetic current were performed by the method.

  That is, with respect to the sample 23 arranged in the same manner as in FIG. 5, a superconducting magnet (not shown) was used, a −5T DC magnetic field was applied for 1 minute at a temperature of 300 K, and magnetic field polarization was performed in the direction of arrow B. . Next, after applying an electric field of 4 to 8 kV / cm between the surface electrodes 22a and 22b in this state and changing from −5T to −0.5T at a speed of +18 mT / s, The electric and magnetic fields were not applied.

  Next, instead of the DC power source 25 of FIG. 5, an electrometer (US Keithley Instruments, Inc., 6517A) is interposed between the signal line 24a and the signal line 24b, and a magnetic field at a speed of about 1 T / min. The electric charge discharged from the sample at that time, that is, the electromagnetic current was measured with an electrometer.

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

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

  J = dPr / 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 Pr 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 (dPr / dB) (4)

μ ₀ is the vacuum permeability (= 4π × 10 ⁻⁷ H / m).

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

dPr / dB = (dPr / dt) / (dB / dt) = J / (dB / dt) (5)
dB / dt indicates the sweep speed of the magnetic field.

  When the above equation (4) is substituted into the equation (5), the electromagnetic coupling coefficient α can be expressed by the equation (8).

α = (μ ₀ · J) / (dB / dt) (8)

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 the equation (8), the electromagnetic coupling coefficient α increases as the sample having a larger current density J of the electromagnetic current, and as a result, the larger the electric polarization Pr, the larger the electromagnetic effect can be obtained. Becomes a ferromagnetic dielectric.

  Table 1 shows the composition and the electric polarization Pr for each of the sample numbers 1 to 19.

FIG. 7 is a graph plotting the relationship between the ZrO ₂ content molar ratio n and the Fe site defect molar ratio z / 12 z for sample numbers 1 to 19. The horizontal axis represents the molar ratio n of ZrO ₂ , and the vertical axis represents z of the Fe site defect molar ratio z / 12. In the figure, the shaded area is the region X of the present invention.

Sample No. 1 does not contain ZrO _{2, and since} there is no defect at the Fe site, the specific resistance ρ is as low as 7.2 MΩ · cm as described above (see FIG. 4). Electric field polarization could not be performed.

Sample No. 15 has a ZrO ₂ content molar ratio n of 0.2, but the Fe site defect molar ratio z / 12 z is 0.05, which is too small compared to the ZrO ₂ content molar ratio n. Therefore, the specific resistance ρ is small, sufficient insulation cannot be secured, and electric field polarization cannot be performed.

Sample No. 5 has both ZrO ₂ content molar ratio n and Fe site defect molar ratio z / 12 z of 0.5, and a sufficient specific resistance ρ is obtained as described above. Although the insulation was good (see FIG. 4), the electromagnetic current could not be measured at room temperature, and the electric polarization Pr could not be obtained. This is presumably because the helical magnetic order necessary for inducing the electric polarization Pr was not formed although the insulation was good.

  Sample Nos. 7, 11-13, 15 and 18 are all outside the range of region X and have good insulation, but for the same reason as sample No. 5, the electromagnetic current can be measured at room temperature. In other words, the electric polarization Pr could not be obtained.

On the other hand, in sample numbers 2 to 4, 6, 8 to 10, 14, 16, 17, and 19, both x of Ba substitution molar ratio x / 2 and y of Al substitution molar ratio y / 12 are both 1. And the relationship between the ZrO ₂ content molar ratio n and the Fe site defect molar ratio z / 12 z is within the range of the region X, so that the insulation is good and the room temperature is 0.5 μC. It was found that a ferromagnetic dielectric material exhibiting an electromagnetic effect having a favorable electric polarization Pr of / m ² or more can be obtained.

  8 and 9 show the electromagnetic characteristics of Sample No. 19.

FIG. 8 shows the current density characteristics of Sample No. 19, where the horizontal axis represents the magnetic field (T) and the vertical axis represents the current density J (μA / m ² ).

FIG. 9 shows the relationship between the magnetic field of sample number 19 and the electric polarization Pr. The horizontal axis represents the magnetic field (T) and the vertical axis represents the electric polarization Pr (μC / m ² ).

  As shown in FIG. 8, when the magnetic field is swept at a speed of -0.5 T to 0.1 T / s, a substantially positive electromagnetic current flows from the negative field to the vicinity of the zero magnetic field, and the vicinity of the zero magnetic field. It can be seen that even when the polarity of the magnetic field is reversed and a positive magnetic field is applied, the electromagnetic current hardly flows on the negative side.

  When the current density J of the electromagnetic current is integrated, the electric polarization Pr is obtained, and the electric polarization characteristics as shown in FIG. 9 are obtained.

As for this electric polarization Pr, a positive electric polarization Pr is obtained when the magnetic field is from −0.5 T to the vicinity of the zero magnetic field. However, when the polarity of the applied magnetic field is reversed, the electric polarization Pr is also reversed in the negative direction. The electric polarization Pr is almost zero in a magnetic field of about 2T. In Sample No. 19, it was found that ferroelectricity was induced when the magnetic field was in the range of 0 to 1.2 T, and the electric polarization Pr also showed a large value of 3.1 μC / m ² on the negative magnetic field side. Further, when the electromagnetic coupling coefficient α was calculated from the equation (8), the maximum value was obtained at zero magnetic field, and α was 50 ps / m.

Ba substitution molar ratio x / 2 x after firing, Al substitution molar ratio y / 12 y, Fe site defect molar ratio z / 12 z, and ZrO ₂ content molar ratio n to 1 mol of main component However, the ceramic raw materials were weighed so that the chemical components of the grinding medium were mixed into the oxide ceramic so as to have the compositions shown in Tables 2 and 3.

  Thereafter, samples Nos. 21 to 66 were prepared by the same method and procedure as in Example 1.

  And the composition analysis of each sample of the sample numbers 21-66 was performed using ICP method and XRF method like Example 1, and when the crystal structure was confirmed by XRD method, each sample was shown in Table 2 and Table 3. It was confirmed that the composition had a hexagonal Y-type crystal structure.

Next, each sample Nos. 21 to 66 was subjected to a polarization treatment in the same manner and procedure as in Example 1, and then an electromagnetism current was measured to obtain an electropolarization Pr from the electromagnetism current.

  Tables 2 and 3 show the composition and electric polarization Pr for each of the sample numbers 21 to 66.

  Sample No. 35 has an Al substitution molar ratio y / 12 of y as small as 0.7, and therefore, at room temperature, a helical magnetic structure that generates electric polarization Pr is not induced, and an electric current can be measured. There wasn't.

  In Sample No. 36, the substitution molar ratio y / 12 of y was as high as 1.3 and the insulation was good, but a heterogeneous phase was generated. The generation of this heterogeneous phase hinders the expression of the electromagnetic characteristics, so that the electromagnetic current cannot be measured at room temperature, and the electric polarization Pr cannot be obtained.

  In Sample No. 65, x of Ba substitution molar ratio x / 2 is 0.8, and the molar ratio of Sr to Ba is relatively large, so that the insulation is sufficient, but at room temperature, the electromagnetic current Could not be measured, and electric polarization Pr could not be obtained.

  Sample No. 66 has a Ba substitution molar ratio x / 2 x of 1.2, and the molar ratio of Sr to Ba is relatively small. In this case as well, the insulation is sufficient, but at room temperature, the electromagnetism The current could not be measured, and the electric polarization Pr could not be obtained.

On the other hand, Sample Nos. 21-34 and 37-64 have Ba substitution molar ratio x / 2 x of 0.9 to 1.1, and Al substitution molar ratio y / 12 y of 0.8 to 0.8. 1.2, and since the relationship between the ZrO ₂ content molar ratio n and the Fe site defect molar ratio z / 12 z is within the range of the region X, practically sufficient insulation can be secured, In addition, it was confirmed that good results of electric polarization Pr of 0.5 μC / m ² or more were obtained at room temperature.

  It is possible to obtain oxide ceramics that have good insulation and can exhibit ferromagnetic dielectric properties at room temperature and low magnetic field of about 300K. Using these oxide ceramics, various ceramics such as variable inductors, magnetic sensors, and nonvolatile memories Electronic parts can be realized.

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

Claims (5)

The main component has a hexagonal Y-type crystal structure containing at least Sr, Ba, Co, Zn, and Fe, and contains n mol of Zr with respect to 1 mol of the main component,
The Ba is contained in such a form that a part of the Sr is substituted so that x is 0.9 to 1.1 when the content of Ba is x / 2.
At least Al, when the content of Al is y / 12 in terms of molar ratio, a part of the Fe contained in the Fe site is such that y is in the range of 0.8 to 1.2. Contained in a substituted form,
In addition, when the amount of deficiency with respect to the stoichiometric composition of the Fe site is z / 12 in terms of molar ratio, (n, z) is A (0.05, 0.05), B (0 .1, 0.05), C (0.4, 0.35), D (0.4, 0.4), E (0.2, 0.4), F (0.05, 0.1 Oxide ceramics characterized by being in a region surrounded by Formula _{[Sr 2-x Ba x CoZnFe} 12-yz Al y O 22 + nZrO 2] ( although, 0.9 ≦ x ≦ 1.1,0.8 ≦ y ≦ 1.2) , characterized by being represented by The oxide ceramic according to claim 1. 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 claim 1.   The ceramic electronic component according to claim 3, wherein the coil is disposed so as to have an inductance corresponding to a magnetic permeability of the component element body.   5. The ceramic electronic component according to claim 3, wherein an internal electrode is embedded in the component element body.

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