JPS61193419A - Reduction/reoxidation type semiconductor capacitor ceramic composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) This invention relates to a barium titanate-based reduced and reoxidized semiconductor capacitor ceramic composition.

(Prior Art) As conventional semiconductor capacitors, grain boundary insulation type five-surface weir layer type and reduction/reoxidation type capacitors are known.

The reduction and reoxidation type semiconductor capacitor to which this invention is directed is made by heat-treating dielectric ceramic in a reducing atmosphere to convert it into a semiconductor.
Next, heat treatment is performed in an oxidizing atmosphere to form a dielectric layer on the surface, and electrodes are further provided. Therefore, the capacitance, insulation resistance,
Each electrical characteristic such as breakdown voltage or capacitance temperature characteristic is
It has the characteristic that it is greatly influenced by the state of formation of the dielectric layer.

(Problem to be solved by the invention)
'While conventional reduction and reoxidation type semiconductor capacitors have relatively large areal capacitances, they have not yet achieved satisfactory temperature characteristics.

It is known that temperature characteristics are improved by adding a small amount of hismuth (Ri). In the case of dark blue porcelain products in which the hismuth is compressed while heating, the bismuth evaporates during firing and the surface layer becomes uneven, resulting in a non-uniform porcelain composition. For this reason, if the re-oxidation layer, that is, the dielectric layer, is made thinner to make it more compact and more convenient for people to carry, the insulation resistance and breakdown voltage will drop significantly, making it impractical. In other words, the conventional barium titanate-based reduced and reoxidized semiconductor J
As for the J capacitor ceramic composition, one which has good temperature characteristics and other electrical characteristics and which can be made into a small capacitor has not been realized.

Therefore, the main object of the present invention is to provide a reduction and reoxidation type semiconductor capacitor ceramic composition that can provide a capacitor having a relatively large areal capacitance and good temperature characteristics.

(Means for Solving the Problems) This invention uses barium titanate (BaTiO3) as a base and 0.05 to 0.00 cohal 1-(Co.03) oxide.
7% by weight, and 0.2 to 4% niobium oxide (Nb2O5).
This is a reduced and reoxidized semiconductor capacitor ceramic composition containing 0% by weight.

(Effects of the Invention) According to the present invention, it is possible to obtain a capacitor having good temperature characteristics and a large area capacitance. Furthermore, unlike conventional bismuth, there is no substance (composition) that scatters during firing, so not only is there less variation in mass production, but the yield is also higher.
The surface layer can be made dense, and a highly reliable capacitor with high insulation resistance and breakdown voltage can be obtained.

(Example) A capacitor using the reduced and reoxidized semiconductor capacitor ceramic composition of the present invention is produced as follows. That is, the raw material composition is prepared and mixed, this mixture is molded and fired in an oxidizing atmosphere, and then heat treated in an oxidizing atmosphere to make semiconductor porcelain. A semiconductor capacitor is constructed by forming a dielectric layer and further arranging electrodes on the surface.

Real J1! ! Benefit 1- The sample was prepared as follows. BaTiO3, CO2
Weigh O3 (X weight %) and Nb2O, (Y weight %) so that they have the composition shown in Attached Table 1, and put each weighed raw material into a polybot and mix it with an organic binder such as hinyl acetate.
Mixed for 6 hours.

After mixing, the mixture was dehydrated and dried, and passed through a 50-mesh sieve for sieving. Next, it was molded into a disk with a diameter of 10 mm and a thickness of 0.5 mm with one side weighing 2,500 kg/cm2.

The molded disk was fired at 1300 to 1400°C for 2 hours to obtain dielectric porcelain. The dielectric porcelain thus obtained was heat treated in a reducing atmosphere at 800 to 900° C. for 1 hour to obtain semiconductor porcelain. A silver paste for electrodes is applied to the surface of this semiconductor porcelain and baked in an oxidizing atmosphere at 650 to 800°C for 30 minutes to form a dielectric layer and an electrode on the surface of the porcelain. An oxidized semiconductor capacitor was obtained.

Regarding the capacitors created in this way, the dielectric constant (εa t 2O°C) and dielectric loss (DF) at product temperature
, insulation resistance (TR), Curie point (CI)) and temperature characteristics (TC) were measured under the following measurement conditions, and Table 1 was obtained.

However, in order to simplify the comparison with other characteristics, the electrode burning conditions for each sample were adjusted so that the areal capacitance was 350 μF/cm 2 .

Note that the capacitance and dielectric loss are 0. IVr, m, s, I K
This is a value measured at tlz. Regarding capacity, reduction temperature,
Since it changes depending on the reoxidation temperature, the reduction temperature was set so that the porcelain specific resistance after reduction was constant, and the reoxidation temperature was also set to give an areal capacitance of 350 μF/cm 2 . Insulation resistance was measured by applying 12 VD, C for 1 minute. A C boost breakdown method was used. The dielectric constant is 1
．． It was measured at OVr, m, s, I KHz, and the measurement temperature was based on 2O°C.

In addition, those marked with * in Attached Table 1 are outside the scope of this invention, and the others are within the scope of this invention.

Disaster Example 1 As shown in Attached Table 2, BaTiO3, Co2O3 (X weight %), Nb2O5 (Yfi amount %) and 1. , a2O3 or Y2O3 (7% by weight) were weighed, and samples were prepared in the same manner as in Example 1.

Each characteristic of the prepared sample was measured in the same manner as in Example 1 to obtain Attached Table 2.

Example-1 As shown in Attached Table 3, BaTiO3, Co2O3 (X weight%
), Nb2O5 (Y wt%), La2O3 (7 wt%)
Each raw material was weighed in the same manner as in Example 1, so that M n C03 was converted to MnO2 and became α weight %.
A sample was prepared.

Each characteristic of the prepared sample was measured in the same manner as in Example 1 to obtain Attached Table 3.

As is clear from Appended Tables 1 to 3, the reasons for the compositional limitations in the reduced and reoxidized semiconductor ceramic composition of the present invention are as follows.

(1) If CO2O3 is less than 0.05% by weight, the Curie point will be low and the dielectric constant at room temperature will be low. Therefore, when the areal capacitance is set to 350 μF/cm 2 , the reoxidized layer on the surface becomes very thin, and the breakdown voltage and insulation resistance become small.

At the same time, the temperature characteristics also deteriorate. On the other hand, Co2
When Q3 exceeds 0.9% by weight, the Curie point becomes high and the dielectric constant at room temperature becomes low. Therefore, when the areal capacitance is set to 350 μF/cm 2 , the reoxidized layer on the surface becomes very thin, and the breakdown voltage and insulation resistance become small.

(2) If Nb2O5 is less than 0.2% by weight, the Curie point becomes high and the dielectric constant at room temperature becomes low.

Therefore, when the areal capacitance is 350μF/cm2,
The reoxidation layer on the surface becomes thinner, reducing breakdown voltage and insulation resistance. On the other hand, when Nb2o5 exceeds 4.0% by weight,
The cue point becomes higher and the dielectric constant at room temperature becomes smaller.
In addition, angular crystals increase on the surface. Therefore, the areal capacity is 350! When I F is set to 7 cm2, the reoxidation layer on the surface becomes very thin, the breakdown voltage and insulation resistance become small, and the temperature characteristics also deteriorate.

(3) La2O3. The addition of rare earth oxides such as Y2O3 has the effect of increasing the rate of reduction and reoxidation and providing a uniform porcelain composition, thereby improving the breakdown voltage. However, the total weight percent of these rare earth oxides relative to BaTiO3
When it exceeds 3.0, the dielectric constant at room temperature becomes too large, resulting in deterioration of temperature characteristics. Note that this is Ce, Nd
The same results were obtained even when other rare earth oxides were added.

(4) MnCO3 has the effect of improving insulation resistance. However, when M n CO3 exceeds 0.5% by weight in terms of M n 02, the dielectric constant at room temperature becomes small, and when the areal capacitance is set to 350 μF/cm2, the reoxidation layer on the surface becomes very large. It becomes thinner, resulting in lower breakdown voltage and insulation resistance. In addition, due to the addition of Mn, M n C03
However, similar results were obtained even if other manganese compounds were added, and it is sufficient that the amount of any of them does not exceed 0.5% by weight in terms of MnO2.

As described above, according to the above embodiment, as shown in Appendix 4, it is possible to obtain a reduction and reoxidation type semiconductor capacitor with improved electrical characteristics compared to the conventional one.

Claims (1)

[Claims] 1 Barium titanate (BaTiO_3) as a base, 0.05 to 0.7% by weight of cobalt oxide (Co_2O_3) and 0.2 to 4.0% by weight of niobium oxide (Nb_2O_5).
A reduced and reoxidized semiconductor capacitor ceramic composition. 2 Furthermore, at least one kind of rare earth oxide is added to
The reduced and reoxidized semiconductor capacitor ceramic composition according to claim 1, wherein 3.0% by weight is added. 3 Furthermore, manganese (Mn) is converted into manganese oxide (MnO
_2) The reduced and reoxidized semiconductor capacitor ceramic composition according to claim 2, wherein 0 to 0.5% by weight is added in terms of _2).