JP2015010026A - Method for manufacturing dielectric ceramic and dielectric ceramic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing STO based dielectric ceramic having high εeven under a high temperature environment, and the STO based dielectric ceramic.SOLUTION: After a sintered body including a perovskite type compound constituted of an element existing in an A site and including Sr and Sn and an element existing in a B site and including Ti when a composition formula is represented by ABOas a compound is obtained by sintering a non-sintered compact including Sr, Ti and Sn as an element and satisfying each condition that a ratio x of an amount of Sr to an amount of Ti is 0.77≤x≤0.99, and a ratio y of an amount of Sn to an amount of Ti is 0.01≤y≤0.23 when the amount of each element is represented by a mol part under an atmosphere in which Sn can be reduced from a positive tetra-valence to a positive divalence, a part of Sn existing in the A site is moved to the B site by heat-treating the sintered body under an atmosphere in which Sn can be oxidized from a positive divalence to a positive tetra-valence.

Description

The present invention relates to a method for producing strontium titanate (SrTiO ₃ : hereinafter referred to as STO) -based dielectric ceramic, and STO-based dielectric ceramic.

In a perovskite-type compound, a position where the coordination number of oxygen ions is 12 is generally called an A site, and a position where the coordination number of oxygen ions is 6 is called a B site. The element located at the A site is represented by A, the element located at the B site is represented by B, and the composition formula is represented by ABO ₃ .

  STO is a perovskite type compound in which the element present at the A site is Sr and the element present at the B site is Ti. STO has a high specific resistance and is used as a base material for a ceramic dielectric that constitutes a ceramic capacitor that requires a high breakdown voltage.

On the other hand, the relative dielectric constant (ε _r ) of STO is high at extremely low temperatures but low at room temperature or higher. For this reason, it is not easy to increase the capacitance of a ceramic capacitor configured using an STO-based dielectric ceramic.

  In order to solve the above problems, for example, an STO-based dielectric ceramic as described in JP 2010-163321 A (Patent Document 1) has been proposed.

The dielectric ceramic described in Patent Document 1, the main component is represented by _{(Sr 1-xy Sn x Ba} y) TiO 3, and in the above composition formula, x is from 0.005 ≦ x ≦ 0.24, y is It is characterized by 0 ≦ y ≦ 0.25.

Pure STO remains in the paraelectric phase without phase transition from high temperature to absolute zero. On the other hand, in the dielectric ceramic described in Patent Document 1, a predetermined amount of Sn is present at the A site of the STO. Thereby, a phase transition to a ferroelectric phase is generated, and the phase transition temperature is adjusted to improve ε _r .

The Sn ion is basically stable in positive tetravalence, and in that case, it exists at the B site of the perovskite type compound. On the other hand, in Patent Document 1, it is important that Sn is present as a positive divalent ion at the A site of the perovskite type compound, and when Sn is present at the B site, an effect of improving ε _r is expected. I can't.

JP 2010-163321 A

  Since the STO-based dielectric ceramic has a high specific resistance, it is suitable as a dielectric ceramic for an in-vehicle ceramic capacitor in which a sudden high voltage may be applied due to, for example, a surge.

  On the other hand, an in-vehicle ceramic capacitor is assumed to be used as a component of electrical equipment mounted in an engine room that is always in a high temperature environment. For example, a ceramic capacitor used in an ECU (Electronic Control Unit) mounted near the cylinder head of the engine may be exposed to a high temperature of 200 ° C. or higher.

However, although the dielectric ceramic described in Patent Document 1 can improve the ε _r at room temperature as compared with the STO, the ε _r at a high temperature as described above has not been demonstrated.

Accordingly, an object of the present invention is to provide a method for producing an STO-based dielectric ceramic having a high ε _r even under a high temperature environment, and to provide such an STO-based dielectric ceramic.

In order to solve the above problems, the present inventor has conducted intensive research. It has been found that it has a high ε _r and has led to the present invention.

  That is, according to the present invention, the dielectric ceramic manufacturing method and the dielectric ceramic composition can be improved.

  The method for manufacturing a dielectric ceramic according to the present invention includes the following first to third steps.

  In the first step, an unfired molded body containing Sr, Ti, and Sn as elements is prepared. When the amount of each element is expressed in mole parts, the ratio x of the amount of Sr to the amount of Ti is 0.77 ≦ x ≦ 0.99, and the ratio y of the amount of Sn to the amount of Ti is 0.01 ≦ Each condition of y ≦ 0.23 is satisfied.

In the second step, the green body is fired in an atmosphere in which Sn can be reduced from positive tetravalent to positive divalent. By this process, when the composition formula is represented by ABO ₃ as a compound, the element present at the A site includes Sr and Sn, and the element present at the B site includes a perovskite type compound including Ti. A sintered body is obtained.

  In the third step, the sintered body is heat-treated in an atmosphere in which Sn can be oxidized from positive divalent to positive tetravalent. By this step, a part of Sn existing at the A site in the perovskite type compound is moved to the B site.

  The temperature applied in the heat treatment in the third step may be lower than the temperature applied in the firing in the second step.

  Further, the heat treatment in the third step may be performed by changing the atmosphere to an atmosphere in which Sn can be oxidized from positive divalent to positive tetravalent in the temperature lowering process of the firing in the second step.

  The dielectric ceramic according to the present invention contains Sr, Ti, and Sn as elements. When the amount of each element is expressed in mole parts, the ratio x of the amount of Sr to the amount of Ti is 0.77 ≦ x ≦ 0.99, and the ratio y of the amount of Sn to the amount of Ti is 0.01 ≦ Each condition of y ≦ 0.23 is satisfied.

In addition, the compound includes a perovskite compound in which the composition formula is represented by ABO ₃ , the element present at the A site includes Sr and Sn, and the element present at the B site includes Ti and Sn. .

  In the above dielectric ceramic manufacturing method, Sn is once added to the A site of the perovskite type compound based on STO by firing in a reducing atmosphere. Next, a part of Sn existing at the A site is moved to the B site by heat treatment in an oxidizing atmosphere.

  That is, the position of Sn in the perovskite compound is controlled by adjusting the atmosphere during firing and heat treatment.

  Therefore, a dielectric ceramic in which Sn is reliably present at both the A site and the B site of the perovskite type compound based on STO can be efficiently produced.

  If the temperature applied in the heat treatment after firing is lower than the temperature applied in firing, no further grain growth of the dielectric ceramic occurs, so that high specific resistance is maintained and mechanical strength may be reduced. Absent.

  In addition, if the heat treatment after firing is carried out by changing the atmosphere in the temperature lowering process of firing, it is not necessary to transfer to another heat treatment device and raise the temperature from room temperature to the heat treatment temperature again. Consumption can be suppressed.

In addition, the above dielectric ceramic has Sn at both the A site and the B site of STO, so that ε _r at 200 ° C. is 180 or more, and has a high ε _r even in a high temperature environment. .

It is a figure which shows typically the presence position of each element in the perovskite type compound contained in the dielectric ceramic which concerns on this invention. It is the lattice image which observed the perovskite type compound contained in the dielectric ceramic of sample 7 from the [001] direction of the crystal lattice by aberration correction TEM (Transmission Electron Microscope: transmission electron microscope). In the lattice image shown in FIG. 2, along the X1-X1 line in FIG. 2 by mapping analysis using EDS (Energy Dispersive X-ray Spectrometry) attached to the aberration correction TEM. It is a figure which shows the result of having analyzed the kind of element contained in the atomic row of the [001] direction to arrange. In the lattice image shown in FIG. 2, the types of elements included in the atomic sequence in the [001] direction arranged along the X1-X1 line in FIG. 2 by line analysis using EDS attached to the aberration correction TEM. It is a figure which shows the result of having analyzed. It is a figure which shows the change of the temperature characteristic of (epsilon) _{r in} the temperature range of -225 degreeC-200 degreeC in the dielectric ceramic of the samples 1, 7, and 11. FIG. FIG. 6 is an enlarged view of a high temperature region of 50 ° C. to 200 ° C. in the temperature characteristic of ε _r shown in FIG. 5.

-Embodiment-
Embodiments of the present invention will be described below to describe the features of the present invention in more detail.

<Manufacturing method of dielectric ceramic>
The method for manufacturing a dielectric ceramic according to the present invention includes the following first to third steps. Each step will be described in the order of steps.

<First step>
The first step is a step of obtaining a green body.

  First, raw material powder for dielectric ceramic is prepared, and these are slurried, and the slurry is formed into a sheet to obtain a green sheet.

  As the raw material powder for the dielectric ceramic, those containing the perovskite type compound as the compound and the kind and amount satisfying the conditions defined in the present invention can be used.

  As a manufacturing method (synthesizing method) of the perovskite type compound powder, various known methods such as a hydrothermal method, in addition to a solid phase method in which raw materials composed of carbonate and oxide are mixed and calcined are used. Can do. Alternatively, STO produced by a hydrothermal method or the like and Sn material are mixed so that the amount of each element satisfies the conditions stipulated in the present invention, and then calcined to produce a perovskite type compound powder. May be.

  In addition, as the raw material powder of this dielectric ceramic, materials of various forms such as carbonates, oxides, hydroxides, chlorides, etc., the kind of elements and the amount of each element are specified in this invention. It is also possible to use a mixture that satisfies each condition.

  In this case, when the dielectric ceramic is fired, they react to synthesize a perovskite type compound in which the kind of element and the amount of each element satisfy each condition defined in the present invention.

  Further, as the dielectric ceramic raw material powder, a mixture of STO produced by a hydrothermal method or the like and Sn material so that the amount of each element satisfies the conditions defined in the present invention is used. You can also.

  Also in this case, they react during firing of the dielectric ceramic, and a perovskite type compound is synthesized in which the kind of element and the amount of each element satisfy each condition defined in the present invention.

  A necessary number of the obtained green sheets are laminated and thermocompression-bonded to obtain an unfired molded body.

  The compact can also be obtained by a method of compacting a dielectric ceramic raw material powder using a pressing device. Alternatively, the dielectric ceramic raw material powder may be slurried and formed into a thin film using a spin coater or the like on a predetermined substrate, or may be obtained by patterning using an ink jet apparatus or the like.

<Second step>
The second step is a step of obtaining a sintered body by firing in a reducing atmosphere.

The unfired molded body obtained in the first step is fired in an atmosphere in which Sn can be reduced from positive tetravalent to positive divalent. By this process, when the composition formula is represented by ABO ₃ as a compound, the element present at the A site includes Sr and Sn, and the element present at the B site includes a perovskite type compound including Ti. A sintered body is obtained.

  As the heat treatment apparatus used in the second step, various known apparatuses such as a conveyor furnace can be used in addition to a batch furnace.

<Third step>
The third step is a step of adjusting the position of Sn in the perovskite type compound by heat treatment in an oxidizing atmosphere.

  The sintered body obtained in the second step is heat-treated in an atmosphere in which Sn can be oxidized from positive divalent to positive tetravalent. By this step, a part of Sn existing at the A site in the perovskite type compound is moved to the B site, and the dielectric ceramic according to the present invention is obtained.

  As described above, Sn is basically stable in positive tetravalence. Therefore, after sintering the dielectric ceramic in a state where Sn contained in the dielectric ceramic becomes positive tetravalent, reducing the Sn to positive bivalent requires, for example, a heat treatment at a temperature higher than the sintering temperature. It ’s not easy. That is, it is difficult to move Sn present at the B site of the perovskite type compound to the A site while controlling the amount thereof.

  On the other hand, in the method for producing a dielectric ceramic according to the present invention, the dielectric ceramic is sintered in a state in which Sn contained therein becomes positive divalent by firing in a reducing atmosphere. Next, a part of Sn is made to be positive tetravalent by heat treatment in an oxidizing atmosphere.

  As described above, since Sn is stable in positive tetravalence, the oxidation from positive divalent to positive tetravalent was performed when a temperature lower than the temperature applied in firing was applied in an oxidizing atmosphere. Even easily. That is, moving a part of Sn existing at the A site of the perovskite type compound to the B site is considered to be a more preferable method than transferring from the B site to the A site.

  In the third step, after completion of the second step, the obtained sintered body is taken out from the heat treatment apparatus used in the second step, and the atmosphere is such that Sn can be oxidized from positive divalent to positive tetravalent. It can be carried out by moving to another heat treatment apparatus. Alternatively, using the same heat treatment apparatus as used in the second step, the atmosphere is changed to an atmosphere in which Sn can be oxidized from positive divalent to positive tetravalent in the temperature lowering process of the second step. Also good.

<Dielectric ceramic>
The dielectric ceramic according to the present invention satisfies each condition defined by the present invention in terms of type and amount as elements. In addition, the compound includes a perovskite compound in which the composition formula is represented by ABO ₃ , the element present at the A site includes Sr and Sn, and the element present at the B site includes Ti and Sn. .

  The ratio of the amount of elements present at the A site to the amount of elements present at the B site is 1.00 stoichiometrically. However, it may deviate from the stoichiometric composition depending on the amount of Sr, Ti and Sn and the position of Sn in the perovskite type compound.

  The dielectric ceramic according to the present invention can be used for a dielectric of a ceramic capacitor as an in-vehicle electronic component. Moreover, you may use for the insulating film of the on-chip capacitor for EMC (Electro-Magnetic Compatibility) of a vehicle-mounted IC, etc.

-Experimental example-
Next, the present invention will be described more specifically based on experimental examples. These experimental examples are also provided to provide a basis for defining conditions for the amount of elements contained in the dielectric ceramic according to the present invention.

<Production of raw material powder for dielectric ceramic>
SrCO ₃ as a raw material of Sr contained in the dielectric ceramic, TiO ₂ as a raw material of Ti, and SnO ₂ as a raw material of Sn were prepared. Each powder had a purity of 99% by weight or more.

  In these powders, when the amount of each element is expressed in mole parts, the ratio x of the amount of Sr to the amount of Ti and the ratio y of the amount of Sn to the amount of Ti are the values shown in Table 1. Weighed and prepared. At the time of blending, the blending amount was corrected according to the purity of each powder.

These blended raw material powders were wet-mixed using a ball mill, uniformly dispersed, then dried and crushed to obtain adjusted powders. The obtained adjusted powder was calcined at 1150 ° C. using a batch type heat treatment apparatus, and then pulverized to obtain a dielectric ceramic raw material powder. The oxygen partial pressure (PO ₂ ) inside the heat treatment apparatus during calcination was set to 1 × 10 ⁻¹³ MPa that can reduce Sn from positive tetravalent to positive divalent.

  In addition, Ca may be mixed into the dielectric ceramic raw material powder as an inevitable impurity derived from the blended raw material. Further, when a YSZ (Ytria Stabilized Zirconia) ball is used as a medium during the wet mixing process, Zr, Hf, and Y may be mixed as inevitable impurities. However, since these impurities are extremely small, it has been separately confirmed that they do not affect the effects of the present invention.

  The obtained dielectric ceramic raw material powder was dissolved with an acid and subjected to ICP (Inductively Coupled Plasma) emission spectroscopic analysis.

  As a result, it was confirmed that the dielectric ceramic raw material powder obtained as described above had substantially the same composition as that shown in Table 1.

<Manufacture of dielectric ceramic>
An organic solvent such as polyvinyl butyral binder, plasticizer, and toluene was added to the dielectric ceramic raw material powder prepared above, and wet mixed by a ball mill for 24 hours to obtain a slurry containing the dielectric ceramic raw material powder. .

  These slurries were formed into a sheet shape on a carrier film made of polyethylene terephthalate by a doctor blade method to obtain a green sheet containing a dielectric ceramic raw material powder.

  An appropriate number of the above green sheets were stacked, thermocompression bonded for 2 minutes under a hydrostatic pressure of 200 MPa, and then cut to obtain an unfired molded body corresponding to each composition shown in Table 1. The outer dimensions of the green body thus obtained were 4.0 mm in width, 4.0 mm in length, and 0.5 mm in thickness.

The unfired molded body was held in the atmosphere at a temperature of 280 ° C. for 6 hours to burn the contained binder. The green body after burning the binder was fired in a reducing atmosphere using a mixed gas of N ₂ —H ₂ —H ₂ O at a temperature of 1300 ° C. for 2 hours. Sintered bodies corresponding to the indicated compositions were obtained. The PO ₂ inside the heat treatment apparatus during firing was set to 1 × 10 ⁻¹³ MPa so that Sn can be reduced from positive tetravalent to positive divalent. The outer dimensions of the obtained sintered body were 3.6 mm in width, 3.6 mm in length, and 0.46 mm in thickness.

  The sintered body was heat-treated in the atmosphere under the conditions shown in Table 1.

  Through the above steps, dielectric ceramic single plates according to Samples 1 to 11 were obtained.

<Manufacture of ceramic capacitors>
On both main surfaces of the above dielectric ceramic single plate, a conductive paste containing Ag as a conductive material and containing a B ₂ O ₃ —SiO ₂ —BaO glass frit is applied, and in an N ₂ atmosphere, An electrode was formed by baking at a temperature of 600 ° C. Thus, a single plate type ceramic capacitor in which a single plate of dielectric ceramic according to Samples 1 to 11 was sandwiched between two electrodes was manufactured.

<Analysis of dielectric ceramic>
The electrodes of the ceramic capacitors according to Samples 1 to 11 were removed, the obtained dielectric ceramic was dissolved with an acid, and the obtained solution was subjected to ICP emission spectroscopic analysis. At that time, 10 dielectric ceramic veneers per solution were made into solution. Here, the dielectric ceramic single plate obtained by removing the baked electrode was melted and analyzed by ICP emission spectroscopy. The dielectric ceramic in the actual use state affected by the baking of the electrode was analyzed. This is because of the target. Subsequent analysis and measurement are based on the same concept. There is no particular restriction on the method of dissolving the dielectric ceramic single plate to obtain a solution.

  As a result, it was confirmed that the dielectric ceramic had substantially the same composition as the composition shown in Table 1.

  Accordingly, the types of elements contained in the dielectric ceramic according to the present invention and the conditions for the amount of each element shall be defined based on the compositions shown in Table 1.

  Next, the electrodes of the ceramic capacitors according to Samples 1 to 11 were removed, and the obtained dielectric ceramic veneer was pulverized and powdered, and contained by X-ray diffraction using a diffractometer The crystal phase was identified. At that time, 10 dielectric ceramic veneers were pulverized per sample.

  As a result, it was confirmed that all the samples 1 to 11 contained a perovskite type compound based on STO as the compound. FIG. 1 is a schematic diagram showing the position of each element in the perovskite compound 1 based on STO.

  The perovskite type compound 1 contained in the dielectric ceramic according to the present invention includes, as described below, elements present at the A site 2 containing Sr and Sn, and elements existing at the B site 3 containing Ti and Sn. It is configured to include.

  Next, the electrodes of the ceramic capacitors according to Samples 1 to 11 were removed, and the obtained dielectric ceramic single plate was processed by polishing, Ar ion milling, or the like to reduce the thickness.

  The dielectric ceramic thin films according to Samples 1 to 11 were observed from the [001] direction of the perovskite compound 1 using an aberration correction TEM to obtain lattice images. At that time, lattice images were obtained from 10 dielectric ceramic thin films per sample.

  As an example, FIG. 2 shows a lattice image of the perovskite compound 1 obtained from one of ten thin films of dielectric ceramic of Sample 7. This lattice image is a view of the A site atom sequence 4 aligned in the [001] direction and the oxygen-B site atom sequence 5 aligned in the [001] direction in FIG.

  The X1-X1 line in FIG. 2 represents the (110) plane viewed from the [001] direction, and the A site atom sequence 4 and the oxygen-B site atom sequence 5 are included in the (110) plane. It is an atomic sequence (see FIG. 1).

  In the lattice image shown in FIG. 2, the elements contained in the atomic sequence in the [001] direction arranged along the X1-X1 line in FIG. 2 are analyzed by mapping analysis using EDS attached to the aberration correction TEM. The results are shown in FIG. Further, FIG. 4 shows the result of analyzing the elements included in the atomic sequence in the [001] direction arranged along the X1-X1 line in FIG. 2 by line analysis using the same EDS. In FIG. 4, the analysis results of the respective elements are shown in a superimposed manner so that the relationship between the positions of the respective elements can be understood.

  3 and 4, the signal intensity of each element is normalized with the maximum value of the signal intensity of each element being 1, and does not represent the absolute value of the signal intensity of each element. Therefore, the comparison of the signal intensity itself is meaningless, and it cannot be determined from the comparison which elements are present in the A site and the B site of the perovskite compound 1. Note that the analysis result for the oxygen-B site atom sequence 5 is that oxygen is a light element and is not detected by EDS, so only the element located at the B site 3 is detected.

  In the mapping analysis of FIG. 3, a signal having an intensity of less than 0.5 is determined as a background signal, and is not shown for easy understanding of the types of elements included in the atomic sequence. On the other hand, in the line analysis of FIG. 4, the analysis results are shown without modification. Therefore, it seems that Ti is detected from the A site atom sequence 4 and Sr is detected from the oxygen-B site atom sequence 5, which is considered to be caused by the background signal as described above.

  3 and 4, Sn is detected from both the A site atom string 4 and the oxygen-B site atom string 5 in this sample. That is, it can be seen that Sn exists in both the A site 2 and the B site 3.

  In the dielectric ceramic thin films according to Samples 1 to 11, the above-described method is performed with respect to a total of six atomic strings of three A-site atom strings 4 and three oxygen-B site atom strings 5 per thin film. The elemental analysis was performed. The number a in which Sn was detected from all three A-site atom strings 4 and the number b in which Sn was detected from all three oxygen-B site atom strings 5 were counted. This elemental analysis was performed on 10 dielectric ceramic thin films per sample.

  For example, in the A-site atom sequence 4, when the number of thin films in which Sn is detected from all three locations is 7, and the number of thin films in which Sn is detected from one location is 3, 7/10 And count. And in the case of 10/10, it determined with the element which exists in A site 2 of the perovskite type compound 1 containing Sn.

  Similarly, with respect to ten thin films, when the count number of Sn in the oxygen-B site atomic sequence 5 is 10/10, it is determined that the element present at the B site 3 of the perovskite compound 1 contains Sn. did.

<Measurement of ε _r of dielectric ceramic>
For the ceramic capacitors according to Samples 1 to 11, a capacitance temperature characteristic measurement system is used, an AC voltage having a voltage of 1 V _rms and a frequency of 1 kHz is applied, and the capacitance is in a temperature range of −225 ° C. to 200 ° C. Was measured. At that time, the capacitance of three ceramic capacitors per sample was measured, and the average value thereof was obtained as the capacitance at each measurement temperature.

  The measurement system is configured to include an impedance analyzer, a thermostatic bath provided with a measurement terminal in the bath, and a personal computer that controls them and records data.

Ε _r at each measurement temperature of the dielectric ceramic according to each sample was calculated from the capacitance at each measurement temperature and the size of the single plate of the dielectric ceramic.

As an example, a comparison of the temperature characteristics of ε _r between the dielectric ceramics of Samples 1, 7 and 11 is shown in FIGS. FIG. 5 shows a large change in ε _r considered to be derived from a phase transition or the like in a temperature range of −225 ° C. to 200 ° C. On the other hand, FIG. 6 is for clarifying the difference in ε _r of the dielectric ceramics of Samples 1, 7 and 11 in the high temperature range of 50 ° C. to 200 ° C.

  As shown in Table 1 below, sample 1 is pure STO alone, sample 7 is a dielectric ceramic in which Sn is present at both A site 2 and B site 3, and sample 11 is Sn. Is a dielectric ceramic existing only at the A site 2.

5 and 6, the sample 7 has a broad peak in the vicinity of −180 ° C. in the temperature characteristic of ε _r , and the ε _r on the high temperature side is larger than that of the sample 1 and the sample 11 as a whole. You can see that it is getting bigger.

This is presumably because the presence of Sn in both the A site 2 and the B site 3 of the STO causes a phase transition to a ferroelectric phase that was not found in pure STO. This broad peak in the temperature characteristic of ε _r is caused by the change in the size of the ferroelectric phase region with a small size due to temperature and the interaction between the ferroelectric phase regions as in a so-called relaxor material. However, details are unknown.

On the other hand, in sample 11 in which Sn is present only at the A site 2, the phase transition to the ferroelectric phase occurs, but the peak shape is not broader than that of sample 7, and ε _r on the high temperature side is sample 1. It is not larger than.

That is, it can be said that it is important for Sn to be present in both the A site 2 and the B site 3 of the STO in order to increase the ε _r on the high temperature side in the STO.

As described above, the ratio x of the amount of Sr contained in the dielectric ceramic to the amount of Ti, the ratio y of the amount of Sn to the amount of Ti, the heat treatment conditions, the location of Sn in the perovskite type compound, Table 1 summarizes ε _r at 200 ° C.

  In Table 1, the sample number marked with * is a sample deviating from the condition of the amount of each element or the condition of the presence of Sn in the perovskite type compound specified in the dielectric ceramic according to the present invention. .

As shown in Table 1, in each sample in which the amount of each element contained in the dielectric ceramic and the presence position of Sn in the perovskite compound satisfy the conditions stipulated in the present invention, ε _r in is 180 or more. That is, even under a high temperature environment, has been confirmed to have a high epsilon _r.

On the other hand, when the amount of each element and the presence position of Sn do not satisfy the conditions defined in the present invention, ε _r at 200 ° C. of the dielectric ceramic is less than 180, which may be an undesirable result. confirmed.

  Note that the present invention is not limited to the above-described embodiment, and various applications and modifications can be made within the scope of the present invention with respect to the composition of the dielectric ceramic.

1 Perovskite type compound 2 A site atom sequence 3 Oxygen-B site atom sequence

Claims (4)

When the element contains Sr, Ti, and Sn, and the amount of each element is expressed in mol parts,
The ratio x of the amount of Sr to the amount of Ti is 0.77 ≦ x ≦ 0.99, and the ratio y of the amount of Sn to the amount of Ti is 0.01 ≦ y ≦ 0.23.
A first step of preparing an unsintered molded body that satisfies each of the following conditions:
When the green body is fired in an atmosphere in which Sn can be reduced from positive tetravalent to positive divalent, when the composition formula is represented by ABO ₃ as a compound, the element present at the A site is Sr. And a second step of obtaining a sintered body containing a perovskite-type compound that includes Sn and an element existing at the B site containing Ti,
The sintered body is heat-treated in an atmosphere in which Sn can be oxidized from positive divalent to positive tetravalent to move a part of Sn present at the A site in the perovskite type compound to the B site. A method for producing a dielectric ceramic, comprising a third step.   The dielectric ceramic manufacturing method according to claim 1, wherein a temperature applied in the heat treatment in the third step is lower than a temperature applied in the firing in the second step.   The heat treatment in the third step is performed by changing the atmosphere to an atmosphere in which Sn can be oxidized from positive divalent to positive tetravalent in the temperature lowering process of firing in the second step. A method for producing a dielectric ceramic. When the element contains Sr, Ti, and Sn, and the amount of each element is expressed in mol parts,
The ratio x of the amount of Sr to the amount of Ti is 0.77 ≦ x ≦ 0.99, and the ratio y of the amount of Sn to the amount of Ti is 0.01 ≦ y ≦ 0.23.
Meet the requirements of
As a compound, a dielectric composition containing a perovskite type compound in which the composition formula is represented by ABO ₃ , the element present at the A site includes Sr and Sn, and the element present at the B site includes Ti and Sn. Body ceramic.