JPH0812329A - Production of ceramic powder and production of ceramic electronic parts - Google Patents

Abstract

PURPOSE:To stably obtain a sintered compact excellent in electrical characteristics and having satisfactory reliability by firing at a low temp., by synthesizing ceramic powder having a perovskite compsn. represented by the general formula ABO3 and contg. Pb as one of elements constituting the site A with a specified aq. soln. CONSTITUTION:When ceramic powder having a perovskite compsn. represented by the general formula ABO3 and having two or more kinds of elements in at least one of the sites A, B is prepd., a compd. of a metallic element selected from among elements constituting the site A and elements constituting the site B is mixed with powder having 5-50m<2>/g specific surface area synthesized with an aq. soln. contg. all the elements constituting the sites A, B except the selected metallic element to produce the objective ceramic powder. The metallic element is an element accounting for the max. content in the site A or B consisting of two or more kinds of elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a ceramic powder and a method for producing a ceramic electronic component using the same.

[0002]

2. Description of the Related Art Ceramic electronic parts such as ceramic capacitors in which a dielectric ceramic is interposed between electrodes have been widely known, and many dielectric ceramics can be suitably used for such ceramic electronic parts. Being developed. When considering a laminated type element here, since the electrode layer and the ceramic layer are integrally fired, it is necessary to use an electrode material that is stable even at the firing temperature of the ceramic material. Therefore, if the firing temperature of the ceramic material is high, an expensive material such as Pt or Pd must be used, so that an inexpensive material such as Ag can be used.
For example, it is required that firing at a low temperature of about 1150 ° C. or less is possible.

As a concrete example of the dielectric ceramic as described above, a perovskite composition based on BaTiO ₃ (barium titanate) and containing stannate, zirconate, titanate or the like as a solid solution is conventionally used. Used from. However, the firing temperature for BaTiO ₃ -based materials is
Since the temperature is as high as 1300 to 1400 ° C., it is necessary to use an expensive material such as Pt and Pd that can endure at high temperature as an electrode material, which causes a high cost.

Various compositions have been studied in order to solve the problems of the BaTiO ₃ system. For example, those mainly containing iron and lead niobate (JP-A-57-57204) and those mainly containing magnesium and lead niobate (JP-A-55-517).
59), those mainly containing magnesium and lead tungstate (JP-A-55-144609), those mainly containing magnesium, iron and lead tungstate (JP-A-58-217462)
There is a lead-containing perovskite composition such as, but the dielectric constant is high, its temperature change is small over a wide temperature range such as -55 ° C to 125 ° C, and it is a dielectric excellent in various electrical characteristics such as withstand voltage. At present, ceramics have not been obtained. Further, studies have been conducted to obtain good temperature characteristics by mixing compositions having different temperature characteristics of permittivity. For example, JP-A-59-203759 discloses mixing of lead composite perovskite compositions (relaxers). However, the temperature coefficient of capacity (TCC) is large and the temperature characteristics are not sufficient.

Further, a lead-containing perovskite composition mainly composed of zircon / lead titanate is disclosed in Japanese Patent Laid-Open No. 5-152158 as a dielectric ceramic having excellent electric characteristics as described above and having extremely excellent temperature characteristics. Is disclosed in. Therefore, even in such a composition, BaTiO 3
_It can be fired at a lower temperature than the ₃ series, but the firing temperature is 12
Since the temperature is still as high as 00 to 1250 ° C., when applied to a laminated ceramic capacitor, an inexpensive Ag / Pd alloy cannot be used as an electrode material, and further lowering of the firing temperature has been desired.

On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 3-120221 reports that the firing temperature of the lead-containing perovskite composition can be lowered by using the ceramic powder synthesized by the hydrothermal synthesis method. However, when a ceramic powder of a lead-containing perovskite composition having a large number of constituent elements is synthesized by a hydrothermal synthesis method, the molar ratio A between the A-site constituent element and the B-site constituent element of the perovskite composition represented by the general formula ABO ₃ / B tends to vary, and it is difficult to always obtain a highly reliable sintered body having a high dielectric constant. Yamamoto et al., Proceedings of 7th Ferroelectric Application Conference (1989) p.
41-42 etc., the powder containing Zr, Ti which is the B site constituent element of zircon / lead titanate was synthesized by the hydrothermal synthesis method, and then the compound of Pb which is the remaining A site constituent element was mixed. Although a technique for preparing a ceramic powder has been proposed, it is extremely difficult to obtain a dielectric ceramic having a high dielectric constant by firing at a low temperature also in this case.

[0007]

As described above, it has been attempted to use the ceramic powder synthesized by the hydrothermal synthesis method from the viewpoint of lowering the firing temperature of the ceramic material. The thermosynthetic powder has problems such as large variation in composition, and as a result, it has not been possible to stably obtain a sintered body having excellent electrical characteristics and good reliability.

The present invention solves such a problem, and a ceramic powder capable of stably obtaining a sintered body having excellent electrical characteristics, good reliability, and less variation in composition by firing at low temperature. It is an object of the present invention to provide a body manufacturing method and a ceramic electronic component manufacturing method using the ceramic powder.

[0009]

Means and Actions for Solving the Problems In order to achieve the above object, the present invention is such that, when represented by the general formula ABO ₃ , at least one of the A site constituent element and the B site constituent element is composed of two or more kinds of components. In preparing a ceramic powder having a perovskite composition, a compound of a metal element of one of the A-site constituent element and the B-site constituent element,
A method for producing a ceramic powder, comprising: mixing a powder having a specific surface area of 5 to 50 m ² / g, which is synthesized by using an aqueous solution containing all the A site constituent elements and B site constituent elements other than the metal element, Provided is a method for producing a ceramic powder in which the metal element is a component having the maximum content in the site among the constituent elements of the site composed of two or more kinds of components. Thus, the method for producing the ceramic powder of the present invention is
When represented by the general formula ABO ₃ , A site constituent element and B
Regarding a ceramic material having a perovskite composition in which at least one of site constituent elements is composed of two or more components, an aqueous solution is used as a powder containing all constituent elements except one main constituent element of the site composed of two or more constituents. And a compound of the main constituent element is mixed with this powder to prepare a ceramic powder. In the present invention, the contents of the constituent elements as described above all mean values in terms of mol.

That is, the inventors of the present invention have conducted research on the reason why there is a large variation in composition in the conventional hydrous synthetic powder of a lead-containing perovskite composition, and as a result, the content of the perovskite composition composed of various constituent elements is particularly high. It was found that it is difficult to always control the amount of precipitation of this component to be constant during the synthesis of the hydrothermal synthetic powder when there are many components. The present invention has been made on the basis of such knowledge, and for the constituent element having the maximum content in the A site or the B site, by separately mixing the compound with a powder synthesized using an aqueous solution, It is to prepare a ceramic powder with a very small variation in composition.
In addition, when the compound of one main constituent element is separately mixed with the powder synthesized by using the aqueous solution to prepare the ceramic powder having the desired perovskite composition,
The manufacturing cost is lower than when a powder containing all the A site constituent elements and the B site constituent elements is synthesized using an aqueous solution. However, in the present invention, when the compound as described above, which is separately mixed with the powder synthesized by using the aqueous solution,
If it is more than one kind, it will be difficult to uniformly mix these two or more kinds of compounds and the powder synthesized using the aqueous solution, and again it is impossible to prepare a ceramic powder having a small variation in composition.

Further, in the preparation of the ceramic powder having the perovskite composition, the compound of the metal element which constitutes the A site or the B site alone and the powder containing the other constituent elements synthesized by using the aqueous solution are mixed. In this case, the powder synthesized by using the aqueous solution does not contain the A site constituent element or the B site constituent element at all.
Thus, in the ceramic powder prepared in this way, uniform diffusion of the A site constituent element and the B site constituent element does not proceed sufficiently by low temperature firing, and the perovskite ratio is high and the electrical characteristics are excellent. It is impossible to obtain a sintered body. Therefore, in the present invention, it is necessary to separately mix the metal element, which is a constituent element of the site composed of two or more kinds of components and has the largest content in the site, with the powder synthesized by using the aqueous solution.

However, in the present invention, the metal element is A
Even if you don't configure a site or B site alone,
If the content of other components constituting the same site is too small, it may not be possible to obtain a sintered body having a high perovskite ratio. Therefore, the molar ratio of the metal element at that site is 99% or less, and It is preferably 95% or less. When both the A site and the B site are composed of two or more kinds of components, whichever of the metal element having the largest content in the A site constituent element and the largest content in the B site constituent element is May be separately mixed with the powder synthesized using an aqueous solution. In the present invention, the metal element separately mixed with the powder synthesized using the aqueous solution as described above may be mixed with the powder synthesized entirely using the aqueous solution, or a part thereof The powder containing other constituent elements may be synthesized using an aqueous solution and the rest may be separately mixed, but it is preferable to mix the whole with the powder synthesized using the aqueous solution, because it is simple in terms of production.

Examples of the compound of the metal element that can be used in the present invention include oxides, chlorides, carbonates, nitrates and oxalates. On the other hand, when a powder containing a constituent element other than the metal element is synthesized using an aqueous solution, for example, a hydrothermal synthesis method, a coprecipitation method, a sol-gel method using a metal alkoxide, etc. may be used. The hydrothermal synthesis method is particularly preferable in that powder having an extremely fine particle size can be synthesized and firing at low temperature is possible. Moreover, the powder synthesized by the hydrothermal synthesis method has a very high activity, and it is possible to further lower the firing temperature by increasing the temperature rising rate during firing. In particular,
It suffices to prepare an aqueous solution containing constituent elements other than the metal element, and subject this aqueous solution to high temperature and high pressure treatment in a pressure vessel to precipitate powder in the aqueous solution.

In the present invention, the powder containing the constituent elements other than the metal element may be synthesized using an aqueous solution and then heat treated at a temperature of about 300 to 1000 ° C. Such heat treatment promotes the formation of a perovskite structure in the powder, and consequently contributes to an increase in the perovskite ratio in the sintered body after firing the ceramic powder. Further, it is needless to say that the heat treatment may be performed after the compound of the metal element is mixed, and may be performed before and after the compound of the metal element is mixed with the powder synthesized using the aqueous solution. Nor. Here, the temperature of the heat treatment is set to 300 to 1000 ° C. When the temperature is less than 300 ° C., the formation of the perovskite structure is hardly promoted, and when it exceeds 1000 ° C., the activity of the powder may be lost and the firing temperature may increase. Because there is. Furthermore, the more preferable heat treatment temperature is 500 to 900 ° C.

In the method for producing ceramic powder of the present invention,
As described above, it is necessary to control the specific surface area of the powder synthesized using the aqueous solution to 5 to 50 m ² / g. If the specific surface area is less than 5 m ² / g, it is difficult to sufficiently homogenize the mixing with the compound of the metal element to prepare a ceramic powder having a small compositional variation, and the firing temperature is high. Tends to become. On the other hand, the specific surface area is 50 m ^2.
If it exceeds / g, it becomes difficult to form the ceramic powder into a predetermined shape. A more preferable specific surface area of the powder is 5 to ²⁰ m ² / g.

Further, the powder synthesized by using the above-mentioned aqueous solution may aggregate and reduce the specific surface area when dried after the synthesis. Therefore, the specific surface area is 5 to 5 if necessary.
It is preferable to pulverize the agglomerated powder so as to obtain 50 m ² / g. Further, the ceramic powder prepared by mixing the powder of the metal element with the powder synthesized using this aqueous solution also has a specific surface area of 5 to 50 m ² / g from the viewpoint of lowering the firing temperature. Is 5 to ²⁰ m ²
It is preferable to control to / g.

The method for producing a ceramic powder of the present invention is a ceramic material having a perovskite composition in which at least one of the A-site constituent element and the B-site constituent element is represented by the general formula ABO ₃ If it is possible, it is applicable without particular limitation. However, when the A site has a perovskite composition in which the A site is composed of two or more components and the main constituent element is lead,
The method for producing ceramic powder of the present invention is particularly effective. That is, an aqueous solution containing a large amount of lead is generally p
It is difficult to control H, and variations in composition are particularly likely to occur in powder synthesized using such an aqueous solution. On the other hand, in the present invention, a powder containing all the constituent elements except lead is synthesized using an aqueous solution, and PbO, PbO ₂ , Pb ₃
A lead-containing perovskite composition having a large variation in composition when the ceramic powder is synthesized by using an aqueous solution by separately mixing a compound of lead such as O ₄ with this powder is also used. It is possible to avoid the variation of.

In the present invention, the elements constituting the A site in the general formula ABO ₃ include Pb, Ba, Sr, Ca,
La and the like are listed, and as the B site constituent element, Zr,
Ti, Zn, Nb, Mg, Fe, Mn, Sn, W, C
Examples include u, Ni, Ta and the like. The general formula ABO ₃
The perovskite composition represented by, may be a composition system in which a glass component, manganese oxide, cobalt oxide, silicon oxide, silver oxide, palladium oxide, etc. are added and contained, and these additional components are used for the preparation of ceramic powder. Therefore, it may be contained in the powder synthesized using the aqueous solution, or may be separately or simultaneously mixed with the powder synthesized using the aqueous solution together with the compound of the metal element. In addition, the general formula ABO
It goes without saying that there is no problem even if it deviates from the stoichiometric ratio of the perovskite composition represented by ₃ . Specifically, JP-A-59-181407, JP-A-61-101460, JP-A-61-155245, JP-A-61-251563, and JP-A-62-26705.
JP-A-62-153162, JP-A-63-233037, JP-A
3-218958, JP-A-4-19961, JP-A-5-152158, JP-A-59-203759, JP-A-57-57204, JP-A-55-51759
The method for producing a ceramic powder of the present invention can be preferably applied to the perovskite composition disclosed in JP-A-58-217462 and the like.

Next, regarding a ceramic electronic component manufactured using the ceramic powder prepared as described above,
Briefly explained. FIG. 1 is a perspective view showing a schematic structure of a monolithic ceramic capacitor with one part cut away as an example of such a ceramic electronic component. As shown in the figure, a multilayer ceramic capacitor is generally formed by repeatedly stacking a plurality of dielectric ceramic layers 1 and internal electrode layers 2 such that the internal electrode layers 2 are alternately exposed on both end surfaces of the multilayer body. A pair of external electrodes 3 to which the internal electrode layers 2 are connected are formed on both end surfaces of the laminated body.

In the method for manufacturing a ceramic electronic component of the present invention, for example, first, a binder, a solvent and the like are added to ceramic powder to form a slurry, and a green sheet which becomes a dielectric ceramic layer after firing is formed. Next, an internal electrode layer is printed on this green sheet, a predetermined number of layers are laminated, pressure-bonded and then cut to produce a chip-shaped molded body. Next, the molded body is degreased and fired, and external electrodes are baked on the obtained sintered body to manufacture a monolithic ceramic capacitor.

Here, a laminated type element is shown as the ceramic electronic component, but in the present invention, the ceramic powder as described above is used to manufacture a ceramic electronic component having a single ceramic layer. Good. Further, the ceramic material to which the present invention can be applied is not limited to a dielectric at all, and even if the present invention is applied to a piezoelectric body, a superconductor, etc., a sintered body with a small variation in composition can be stably obtained. As a result, it is expected that the electric characteristics and reliability of the ceramic electronic component will be improved.

[0022]

EXAMPLES Examples of the present invention will be shown below. Example 1 First, as a starting material, Ca, Zr, and Ti hydroxides, nitrates, or chlorides were mixed at a predetermined mixing ratio, hydrothermally treated in an aqueous solution, and dried to obtain a powder having a specific surface area of 12 m ² / g. Synthesized. Next, a predetermined amount of PbO was mixed with this hydrothermally synthesized powder, and then pulverized with a ball mill or the like for 24 hours until the specific surface area became 12 m ² / g, (Pb _0.78 Ca _0.22 ) (Zr _0.7
Sample N having a perovskite composition of Ti _0.3 ) O _3.
A ceramic powder of o.1 was prepared. On the other hand, for comparison, P
A hydrothermal synthetic powder containing all the constituent elements of b, Ca, Zr, and Ti was synthesized in the same manner, and the specific surface area after drying was 12 m ² /
The ceramic powder of Sample No. 2 having the same composition as that of Sample No. 1 was prepared by pulverizing until it reached g.

With respect to each of these ceramic powders, 20 lots were chemically analyzed for the molar ratio A / B of the A site constituent element and the B site constituent element. The results are shown in Figure 2.
In the figure, the black circles show the analysis results of the sample No. 1 ceramic powder, and the white circles show the analysis results of the sample No. 2 ceramic powder. As shown in FIG. 2, there is very little variation in the composition of sample No. 1 ceramic powder A / B = 1.00 ±
Although it was 0.01, the composition of the ceramic powder of sample No. 2 had a very large variation in composition A / B = 1.00 ± 0.1
It was 5.

Further, the specific surface area after drying containing only Zr and Ti in the constituent elements of A site and B site is 12 m ²
/ G of powder was synthesized by hydrothermal treatment in an aqueous solution. Next, this hydrothermal synthetic powder is mixed with PbO and CaO and pulverized for 24 hours by a ball mill etc. until the specific surface area reaches 12 m ² / g, and the ceramic powder of sample No. 3 having the same composition as sample No. 1 Was prepared. Here, sample Nos. 1 to 3 as described above
Concentration distributions of constituent elements in one particle of the ceramic powder of No. 1 were measured by an analytical electron microscope. As a result, the sample
In the case of the No. 1 ceramic powder, the Pb concentration was relatively high and uniform near the surface of the particles, and the concentration of each constituent element for each particle was also relatively uniform. Particles with non-uniform Pb concentration were present in the vicinity of the surface. On the other hand, since the ceramic powder of sample No. 3 was a mixture of two kinds of compounds and hydrothermal synthetic powder, the Pb concentration distribution was non-uniform, and the concentration of each constituent element for each particle was poor. understood.

Next, a binder was added to each of the ceramic powders of Sample Nos. 1 to 3 to have a diameter of 14 mm and a thickness of 1.5 m.
A molded body of m was produced. Subsequently, when these compacts were first fired at 1050 ° C. for 2 hours, a sintered compact densified to 97% of the theoretical density was obtained for the ceramic powder of sample No. 1, and in this sintered compact Perovskite rate calculated from the peak ratio by X-ray diffraction measurement is 100%
The relative dielectric constant was 1400. However, sample N
The ceramic powder of o.2 may be densified up to 97% of the theoretical density due to the variation in composition between lots as described above, but may not be sintered at all. Even between the bodies, the perovskite rate and the relative permittivity varied within the ranges of 35 to 100% and 400 to 1400, respectively. The densification of the ceramic powder of sample No. 3 proceeded only up to 81% of the theoretical density, and the perovskite ratio was 85% and the relative dielectric constant was 800. Separately from this, a ceramic powder of sample No. 3 was molded into the same shape and fired at 1200 ° C. for 2 hours. As a result, the theoretical density was 96%, the perovskite ratio was 93%, and the relative dielectric constant was 120.
A sintered body of 0 was obtained. Therefore, in the ceramic powder of Sample No. 3 prepared by mixing the hydrothermal synthetic powder containing no A-site constituent element and the compound of the A-site constituent element, the A-site constituent element and the B-site constituent element were obtained by low temperature firing. It was confirmed that the uniform diffusion with and did not proceed sufficiently, and a sintered body having a high perovskite ratio and excellent electrical characteristics could not be obtained.

In addition, 800 is added to the ceramic powder of sample No. 1.
After heat treatment at ℃ × 1 hour, the specific surface area is 12m ² /
The mixture was pulverized to a weight of g, a binder and an organic solvent were added to form a slurry, and a doctor blade type sheet forming machine was used to form a green sheet having a thickness of 38 μm. Next, 70 wt% Ag / 30 was used as an internal electrode layer on this green sheet.
A wt% Pd paste was printed in a predetermined shape, 60 sheets were stacked, pressure-bonded, and then cut to produce a chip-shaped molded body. Next, this molded body is degreased and fired at 1050 ° C. for 2 hours, and Ag paste as an external electrode is baked at 800 ° C. on the obtained sintered body to manufacture 100 multilayer ceramic capacitors of 4.5 × 3.2 mm. did. The capacitance of these multilayer ceramic capacitors measured by a digital LCR meter under the condition of 1 kHz is 0.32 ± 0.0.
It was 2 μF. Furthermore, the same multilayer ceramic capacitor was manufactured 20 times and the variation between manufacturing lots was examined. As a result, the capacitance was 0.32 ± 0.03 μF and the variation rate was 9%.
And was very small.

On the other hand, regarding the ceramic powder of sample No. 2,
Similarly, when a monolithic ceramic capacitor was manufactured and variation between manufacturing lots was examined, the capacitance was 0.27 ± 0.08μ.
In F, the variation rate was as large as 30%. Moreover, in the case of the ceramic powder having A / B exceeding 1.10, there was a case where the capacity could not be obtained by reacting with the internal electrode layers during firing. We also attempted to manufacture a monolithic ceramic capacitor for sample No. 3 ceramic powder.
A dense sintered body could not be obtained by firing for 2 hours, and as a matter of course, the capacity could not be obtained.

Further, for each of 50 ceramic capacitors manufactured using the ceramic powders of Sample Nos. 1 and 2, a DC voltage of 50 V was applied in a high temperature and high humidity condition of 85 ° C. and 95% RH to perform a moisture resistance load test. And the capacitance resistance product is 1Ω
・ F or less was judged as a defective product, and the reliability was evaluated by the number of defective products after 500 hours. As a result, the defective rate after 500 hours was 2% for sample No. 1 and 38% for sample No. 2, and the ceramic capacitor manufactured using the ceramic powder of sample No. 1 was
There were few defects and the reliability was good. Example 2 First, as a starting material, Ba, Mg, Zn, Nb, and Ti hydroxides, nitrates, or chlorides were mixed at a predetermined mixing ratio, hydrothermally treated in an aqueous solution, dried, and then heat-treated at 800 ° C. for 1 hour. Then, a powder having a specific surface area of 15 m ² / g was synthesized. Next, a predetermined amount of Pb ₃ O ₄ was mixed with this hydrothermally synthesized powder and further heat-treated at 800 ° C. for 1 hour, and then the specific surface area was 1
Grind with a ball mill etc. for 24 hours until it reaches 5 m ² / g,
(Pb _0.875 Ca _0.125 ) [(Zn _1/3 Nb _2/3 ) _0.3
A ceramic powder of sample No. 4 having a perovskite composition of (Mg _1/3 Nb _2/3 ) _0.5 Ti _0.2 ] O ₃ was prepared. On the other hand, for comparison, Pb, Ba, Mg, Zn, Nb,
A hydrothermal synthetic powder containing all the constituent elements of Ti was synthesized in the same manner, pulverized after drying until the specific surface area became 15 m ² / g, and the ceramic of sample No. 5 having the same composition as sample No. 4 A powder was prepared. For these ceramic powders,
Chemical analysis of the molar ratio A / B of the A-site constituent element and the B-site constituent element in 20 lots each gave sample N
The ceramic powder of o.4 had very little variation in composition, A / B = 1.00 ± 0.01, but the ceramic powder of sample No. 5 had a very large variation in composition.
B = 1.00 ± 0.19.

Further, a powder having a specific surface area of 15 m ² / g after drying containing only Mg, Zn, Nb, and Ti among the constituent elements of A site and B site was synthesized by hydrothermal treatment in an aqueous solution. Next, PbO and BaO were mixed with this hydrothermally synthesized powder, and the mixture was crushed for 24 hours with a ball mill etc. until the specific surface area became 15 m ² / g. Sample N having the same composition as sample No. 4
A ceramic powder of o.6 was prepared. Here, with respect to the ceramic powders of Sample Nos. 4 to 6 as described above, the concentration distribution of constituent elements in one particle was measured by an analytical electron microscope. As a result, in the ceramic powder of sample No. 4, the Pb concentration was relatively high and uniform near the surface of the particles, and the concentration of each constituent element for each particle was also relatively uniform.
In the No. 5 ceramic powder, particles having a non-uniform Pb concentration near the surface were present. On the other hand, the ceramic powder of sample No. 6 is Pb because it is a mixture of two kinds of compounds and hydrothermal synthetic powder.
It was found that the concentration distribution of was uneven, and the concentration of each constituent element of each particle was inferior in uniformity.

Next, a binder was added to each of the ceramic powders of Sample Nos. 4 to 6 to have a diameter of 14 mm and a thickness of 1.5 m.
A molded body of m was produced. Subsequently, when these compacts were first fired at 950 ° C. for 2 hours, a sintered compact densified to 97% of the theoretical density was obtained for the ceramic powder of sample No. 4, and in this sintered compact, The perovskite ratio calculated from the peak ratio by X-ray diffraction measurement is 100%,
The relative dielectric constant was 12500. However, sample No. 5
Due to the above-mentioned variation in composition between lots, the ceramic powder of may be densified up to 97% of the theoretical density, but may not be sintered at all. However, the perovskite ratio and the relative dielectric constant varied within the ranges of 50 to 100% and 8000 to 12,500, respectively. The densification of the ceramic powder of sample No. 6 proceeded only to 78% of the theoretical density, the perovskite ratio was 78%, and the relative dielectric constant was 9000. Separately from this, a ceramic powder of Sample No. 6 was molded into the same shape and fired at 1050 ° C. for 2 hours. As a result, the theoretical density was 96%, the perovskite ratio was 97%, and the relative dielectric constant was 12%.
000 sintered bodies were obtained. Therefore, in the ceramic powder of Sample No. 6 prepared by mixing the hydrothermal synthetic powder containing no A-site constituent element and the compound of the A-site constituent element, the A-site constituent element and the B-site constituent element were obtained by low temperature firing. It was confirmed that the uniform diffusion with and did not proceed sufficiently, and a sintered body having a high perovskite ratio and excellent electrical characteristics could not be obtained.

A binder and an organic solvent were added to the ceramic powder of sample No. 4 to form a slurry, and a doctor blade type sheet forming machine was used to form a green sheet having a thickness of 38 μm. Next, 70 wt% Ag / 30 wt% Pd paste was printed in a predetermined shape as an internal electrode layer on this green sheet, and 60 sheets were stacked, pressure-bonded and then cut to produce a chip-shaped molded body. Next, after degreasing this molded body, it was fired at 950 ° C. for 2 hours, and Ag paste as an external electrode was baked at 800 ° C. on the obtained sintered body to obtain 4.5.
100 x 3.2 mm multilayer ceramic capacitors were manufactured. For these monolithic ceramic capacitors,
The capacitance measured by a digital LCR meter under the condition of 1 kHz was 2.8 ± 0.05 μF. Furthermore, the same multilayer ceramic capacitor was manufactured 20 times and the variation between manufacturing lots was examined. As a result, the capacitance was 2.8 ± 0.08.
The fluctuation rate at μF was as small as 3%.

On the other hand, regarding the ceramic powder of sample No. 5,
Similarly, when a monolithic ceramic capacitor was manufactured and the fluctuation between manufacturing lots was examined, the capacity was 2.2 ± 0.8 μF and the fluctuation rate was as large as 36%. Moreover, A / B is 1.1
In the case of ceramic powder exceeding 0, there was a case where the capacity could not be obtained by reacting with the internal electrode layers during firing. We also tried to manufacture a monolithic ceramic capacitor for sample No. 6 ceramic powder, but it was not possible to obtain a dense sintered body by firing at 950 ° C x 2 hours, and of course, No capacity was obtained.

Further, for each of 50 ceramic capacitors manufactured by using the ceramic powders of Sample Nos. 4 and 5, a DC voltage of 50 V was applied in a high temperature and high humidity condition of 85 ° C. and 95% RH to perform a moisture resistance load test. Example 1, respectively
Similarly, the reliability was evaluated. As a result, the defect rate after 500 hours was 2% for sample No. 4, while that for sample No. 5
Was 40%, and the ceramic capacitor manufactured using the ceramic powder of sample No. 4 had few defects and had good reliability.

[0034]

As described in detail above, according to the present invention, it is possible to stably obtain a sintered body having excellent electrical characteristics and good reliability and little variation in composition, by firing at low temperature. As a result, it is possible to provide a ceramic powder that is suitably used for manufacturing a ceramic electronic component.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic structure of a monolithic ceramic capacitor with a part cut away.

FIG. 2 is a diagram showing the results of chemical analysis of A / B for 20 lots of each of the ceramic powders of Sample Nos. 1 and 2.

[Explanation of symbols]

1 ... Dielectric ceramic layer, 2 ... Internal electrode layer, 3 ... External electrode.

Claims (4)

[Claims] 1. When preparing a ceramic powder having a perovskite composition in which at least one of an A-site constituent element and a B-site constituent element is represented by the general formula ABO ₃ , the above A-site constituent element is prepared. A compound of one metal element of the elements and B-site constituent elements was synthesized using an aqueous solution containing all A-site constituent elements and B-site constituent elements other than this metal element, and the specific surface area was 5 to 5.
A method for producing a ceramic powder, which is mixed with 50 m ² / g of powder, wherein the metal element is a component having the largest content in the site among the constituent elements of the site composed of two or more kinds of components. A method for producing a ceramic powder, comprising: 2. The method for producing a ceramic powder according to claim 1, wherein the metal element is lead. 3. The method for producing a ceramic powder according to claim 1, wherein the powder is a hydrothermal synthetic powder. 4. A method for producing a ceramic electronic component, comprising the step of producing a molded body of ceramic powder having a predetermined shape and then firing it, wherein the ceramic powder is produced by the method of claim 1. A method of manufacturing a ceramic electronic component, which is prepared by the method.