JPH0215607A - Ceramic capacitor element - Google Patents

Abstract

PURPOSE:To provide the title ceramic capacitor element with sufficient sintering density by low temperature baking process while obviating the structural defect by a method wherein an amorphous body produced by melting and quenching a mixture containing the basic components of specific dielectric material and glass forming component is heat-treated to form a sintered body so that crystalline powder produced by removing the glassy compound from the sintered body may be used. CONSTITUTION:Within a triangle component diagram comprising AO-DO2-B2O3 base components, a mixture contained in a composition region encircled by the lines connecting point of AO 50mole%-B2O3 mole%, the point of DO255 mole%-AO 45mole% and the other point of DO 45mole%-AO 55mole% with one another is melted down. Then, a glassy body produced by quenching the melt is heat-treated to separate out a crystal represented by ADO3. Next, the crystal is crushed to remove the glassy component therefrom by dilute acidic processing for producing the ADO3 crystalline powder to be used. Within the component diagram, A represents at least one element selected from Ba, Be, Mg, Ca, Sr, Ra, while D represents at least one element selected from Ti, Zr, Hf, Th. The reaction to separate said ADO3 crystal is performed very slowly since it depends upon the atomic diffusicn in solid phase so that the separated out ADO3 may be produced in every fine grains in even diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a ceramic capacitor element with sinterability dispersed therein.

[Conventional technology]

Ceramic capacitor elements whose main raw materials are BaT 10B and 8rT103 can be made from CaT 10g-? Appropriate amounts of BaZrO3 and the like are mixed to adjust the temperature characteristics, etc. Such ceramic capacitor elements are manufactured by mixing different types of oxide dielectric powders at a predetermined ratio and using them as a raw material powder, or by using composite oxide current-visitor powders in which some components have been chemically replaced. It is common to For example, B a
In the case of (T I x Zr s −x ) 03, the former uses BaT103 powder and BaZr01 powder at X:1−
The latter method uses Ba("xzrt-x)Oa synthesized so that the ratio of Zr and Zr is mixed in a predetermined ratio.
This method uses powder.

In either case, the oxide dielectric powder used was one manufactured by a method such as a solid phase reaction method, a coprecipitation method, or an alkoxide method. After mixing the oxide dielectric powder obtained by the above method with a binder and molding it into a predetermined shape,
Capacitor elements were obtained by sintering.

[Problem to be solved by the invention]

However, capacitors using the oxide dielectric powder obtained by the above method have the drawback of low sintering density and low sintering strength. Low sintering density and sintering strength cause structural defects such as voids, microcracks, and delaminated areas, reducing product reliability and yield. In order to ensure sufficient sintered density and strength, it is necessary to perform the firing at a high temperature of 1300°C or more over a long period of time. An increase in costs was unavoidable.

In addition, in the case of multilayer ceramic capacitors, internal electrodes are laminated between multiple dielectric layers and fired, so 1300
Electrode materials are limited to materials that can withstand firing temperatures of ℃ or higher. This forced the use of expensive materials such as rounded Pd.

An object of the present invention is to provide a ceramic capacitor element that has sufficient sintered density when fired at a low temperature and is free from the above-mentioned structural defects.

[Means and actions to solve the problem]

The present invention is based on the triangular component diagram of the AO-Do2-B2O3 system (A Fi13a l Be + Mg +
At least one element selected from Ca + S r + 1<a, and D is Ti.

at least one element selected from zr, Hf, Th)
In, the point of 050 mol% - 820,5Q mol%,
A glass body obtained by melting a mixture within the compositional region surrounded by a gland connecting the point DO255 mol% - Human 045 mol% and the point D0245 mol% - Human 055 mol%, and rapidly cooling this melt. This is a ceramic capacitor element characterized by using ADO3 crystal powder obtained by heat-treating ADO3 to precipitate crystals represented by ADO3, pulverizing the crystals, and removing glass components by dilute acid treatment.

Here, the above composition range will be explained.

When the glass body is heat-treated, an As2O3 (or As2O3) phase is first precipitated. This is differential thermal analysis,
It was confirmed from the results of x-glue diffraction that it precipitates preferentially to human DO3. Therefore, A is the basic component of ADO3.
If O is less than the equivalent molar amount of B2O3, human O has B2O
Because it easily combines with 3 to form As2O3, the target A
The amount of DO3 precipitated decreases, and the remainder precipitates as Do2. It is difficult to remove Do2 by dilute acid treatment in the post-process, and it remains in the ADO3 crystal powder, which is not preferable. Furthermore, as the amount of B2O3 increases, the melting temperature of the bath increases, resulting in poor economic efficiency. Considering the above effects, the first
AO shown in the figure, Do2. B2O3% - a-btL in the triangular component diagram with the vertex, that is, 050 mol% -
B2035 Q mole% point and Do2) 5 mole% - person 04
A preferred composition range is a region in which Iwayosumo AO is in excess, connecting the points of 5 mol %.

On the other hand, if ADO3-1-A B is in excess than the number of moles of ADO3-1-A B
204 + 0 people generate. Although ADO3 can be easily removed together with As2O3 by dilute acid treatment, as AO3d increases, the yield of ADO3 decreases, increasing the burden on the dilute acid treatment process and significantly impairing productivity. a CN in the figure, that is, A050 mol%-B10.
5 Q mole% point and Do, 45 mole% - person 055 mole%
A preferred composition range is a region where Do2 is in excess compared to the point where the points are connected.

From the above, the composition in the range surrounded by points II, b, and C in FIG. 1 is selected. Furthermore, as a chemical ratio, d
[tL Ino is a-d 50 mol% of AO indicated by llA
-B20350 mol% point and D0□50 mol%-Person 05
This is a case where the composition is on a line connecting the 0 mol % point.

In the present invention, the glass body is heat-treated to precipitate human D03 crystals from the glass phase. Since this reaction is dominated by atomic diffusion within the solid phase, it is a slow reaction, and it is possible to form the precipitated ADO3 into extremely fine particles with uniform particle size. For this reason, the ceramic capacitor according to the present invention is compact after powder compaction, and shows good sinterability at relatively low temperatures with no gaps between the powder particles.

〔Example〕

Examples of the present invention will be described below with reference to Ba (Ti, xZrX)03(
An example using X=0.2 (the same applies hereinafter) will be described.

In the glass body obtained by melting and cooling the raw material mixture, Ba (T 1l-) (Zrx) 03 : Ba
BaCO3+ H3BO3, TIO□, ZrO, respectively, so that O@B2O3 has a molar ratio of 50:50.
Mix 2 on a specified scale and put it in a platinum crucible, 13
The mixture was melted in a heating bath at a temperature of 00 to 1400°C. This melt was flowed out from a nozzle at the bottom of the platinum crucible, poured onto water-cooled twin rolls, and rapidly cooled to form a flaky glass body. Next, this glass body was crushed, filled into a predetermined container, and placed in an electric furnace. This sintered body was finely pulverized using a ball mill or a vibration mill, and then treated with a 10% acetic acid solution to dissolve and remove glass-forming components. Next, wash with water repeatedly on a stage where the pH of the washing solution becomes 6 or more, and then dehydrate and dry the whole product.
A T i 1-x Z rx ) 03 crystal powder was obtained.

The obtained Ba (T11-xZrx) 03 powder was press-molded into a predetermined shape at a pressure of 1 to 2, and a plurality of molded pieces were prepared and fired at different temperatures between 1000 and 1300°C for 2 hours. Curve A in FIG. 2 shows the results of measuring the sintered density of the ceramic capacitor element thus produced.

In addition, as a comparative example, Ba (TI□-xZrx)03 (X = 0.2) prepared by solid phase reaction method and coprecipitation method
A capacitor element was made using the powder, and the change in sintered density due to firing temperature was investigated using the same machine as in the above example. The results are also shown in Figure 2.

In FIG. 2, curve B shows a comparative example of a product prepared by a solid phase reaction method, and curve C shows a comparative example of a product prepared by a coprecipitation method.

As shown in FIG. 2, the ceramic capacitor element of this example was fired at a firing temperature of 1200°C. A high sintered density of a 1.1 was obtained, and no cracks or voids were observed.

〔Effect of the invention〕

As described above, the ceramic capacitor element of the present invention has sufficient sintered density at a lower firing temperature than conventional ceramic capacitor elements, is free from structural defects such as voids and cracks, and is highly reliable.

Furthermore, since firing is possible at a low temperature, even when laminated, it is possible to increase the proportion of inexpensive materials with equal specific gravity, such as A%, used as internal electrodes, thereby reducing the cost of the product.

[Brief explanation of the drawing]

FIG. 1 is a phase diagram (triangular component diagram) of the AO-DO□-8203 system according to the present invention. FIG. 2 shows Ba(T'
1-X"

Claims (1)

[Claims] Basic components of dielectric materials AO (A is Ba, Be, Mg, Ca
, Sr, Ra) and D
A mixture containing O_2 (D is at least one element selected from Ti, Zr, Hf, and Th) and a glass-forming component is melted, and the amorphous body obtained by rapidly cooling the melt is heat-treated to form ADO_3. A ceramic capacitor element characterized in that it uses ADO_3 crystal powder obtained by pulverizing the sintered body and removing the glass component by treatment with dilute acid.