JPH04112516A - Semiconductor ceramic capacitor of grain-boundary insulation type - Google Patents

Abstract

PURPOSE:To obtain this capacitor by a method wherein a sintering-promoting additive, a semiconductor-promoting additive and a grain-boundary depletion- layer forming agent, in respectively prescribed quantities, are added to a perovskite-type oxide composed mainly of SrTiO3, this mixture is sintered and a diffusion treatment is executed in an oxidizing atmosphere. CONSTITUTION:The following are added to and mixed with a perovskite-type oxide composed mainly of strontium titanate (SrTiO3): 0.1 to 5.0wt.% of a sintering-promoting additive; 0.05 to 2.0wt.% of a semiconductor-promoting additive Nb2O5; and 0.1 to 5.0wt.% of a grain-boundary depletion-layer forming agent composed of Sr1-x-yBaxCay(Co1/3Ta2/3)O3 (where x<=0.3, y<=0.3 and 0<=x+y<=0.6). This mixture is pressurized and molded. Then, the mixture is baked at 1250 to 1500 deg.C in a reducing atmosphere which contains hydrogen. The surface of its baked substance is coated with a grain-boundary diffusing substance which contains bismuth oxide (Bi2O3). A heat treatment is executed at 850 to 1200 deg.C in an oxidizing atmosphere. Electrodes are formed. Thereby, a large element whose characteristic is good can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a grain boundary insulated semiconductor ceramic capacitor, and more particularly to a laminated grain boundary insulated semiconductor ceramic capacitor.

Conventional technology It has been known that by insulating the grain boundaries of this type of ceramic oxide semiconductor, it is possible to obtain a capacitor body with a much larger effective dielectric constant than conventional ceramic dielectrics. It is being For example, SrTiO3 is the main component, and Nb:Or and T 102-A
I: Copper oxide (CuO
) and bismuth oxide (Bi2C1+) are diffused, a depletion layer is formed at the grain boundaries, the grain boundaries are insulated, and electrodes are formed.In the grain boundary insulated semiconductor capacitor, the boost breakdown voltage is 1200 V/shoe, Insulation resistance approximately I x 10'
While maintaining the insulation properties of MΩ/mouth, the effective dielectric constant is 20,
000-100. A large value like OOO is obtained. Note that here, the diffusion substances Cub, Bi2O
Regarding role 3, CuO forms an electron trap center in the grain boundaries of the sintered body, and traps electrons in the crystal grains of the n-type semiconductor crystal near the grain boundaries. , which acts to form a depletion layer without electrons near the grain boundaries. A grain boundary insulated semiconductor ceramic capacitor forms a capacitor by storing charge on both sides of the depletion layer thus formed. On the other hand, Bi2O3 (along with ZrO2, etc.) is known to be a good conductor of this oxygen, existing at grain boundaries and transporting oxygen from the outside to the inside of the sintered body by diffusion, supplying the oxygen necessary for the formation of grain boundary depletion layers. work to do.

However, in contrast to these bulk type capacitors, there is a strong demand for lamination even in grain boundary insulated semiconductor ceramic capacitors.

Problems to be Solved by the Invention However, in order to obtain a large capacitance, grain boundary insulated semiconductor ceramic capacitors obtained by such conventional manufacturing methods are made by making the crystal grains in the sintered body as large as possible and using paste. Bi2O3, CuO, etc. are diffused into the interior of the sintered body by coating the sintered body with oxide containing copper oxide, bismuth, etc., and then applying heat treatment. Although it has gone through the process,
Since the electrode spacing in laminated ceramics becomes narrower, the grain size of the crystal grains in the sintered body must be suppressed.

In addition, in devices manufactured using this conventional method, CuO and the like are less likely to diffuse during the process compared to B1203 and the like.
As a result, the characteristics tend to vary (furthermore, if the device is thick, it is difficult to diffuse copper oxide etc. sufficiently into the inside, so there is a problem such as restrictions on the size of the device.

The present invention solves these problems, namely:
The grain size of the crystal grains in the sintered body is small and uniform, and there is no need to apply or diffuse a grain boundary depletion layer forming agent such as copper oxide, but simply apply a grain boundary diffusion substance such as bismuth oxide. The objective is to obtain large elements with good characteristics simply by performing heat treatment and diffusion in air.

Means for Solving the Problems In order to solve the above problems, the present invention provides a perovskite-type oxide mainly composed of 5rTiO3, with a sintering accelerating additive of 0.61 to 5.0 wt% and a semiconducting accelerating additive of Nb2O.
5 to 0.05 to 2.0 wt%, and S r 1-x-
yB axCa'y (CO1,23T a2z3)
03 (However, X≦13. y≦0.3.0≦X+Y
Grain boundary depletion layer forming agent consisting of ≦0,6) from 0.1 to 5.0
After adding wt%, mixing, printing and molding, sintering at high temperature to make a semiconductor, and then performing a diffusion treatment of bismuth oxide etc. at 850 to 1200°C in an oxidizing atmosphere to obtain a grain boundary insulated semiconductor ceramic capacitor. It is.

Effect: With this configuration, the perovskite-type oxide mainly composed of SrTiO3 and the grain boundary depletion layer forming agent S r +
-x -y Ba yi Ca y (Co +
3T a 23) 03 and semiconductor-promoting additive Nb2O
5 is reacted and dissolved in solid solution, and during the cooling process during firing, oxides containing copper are precipitated at the grain boundaries, and the oxygen that has diffused through the bismuth oxide that has diffused to the grain boundaries further forms copper, etc. By oxidizing the grain boundary material, an electron trap center is formed at the grain boundary, and a depletion layer is formed along the grain boundary within the low-resistance semiconductor crystal formed by reduction. The depletion layer obtained in this way has good insulating properties, and charges can be stored on both sides of the depletion layer, resulting in a high-quality capacitor. That is, according to the present invention, Cu
Excellent grain boundary insulated semiconductor ceramic capacitors can be easily obtained without the need for coating and diffusing O or the like.

EXAMPLE Hereinafter, a grain boundary insulated semiconductor ceramic capacitor according to an example of the present invention will be described with reference to the tables and drawings.

(Example 1) Titanyl strontium oxalate (SrTiO(C204)
Sintering accelerator Tie2-Al□0 is added to strontium titanate (S rTie3) obtained by thermal decomposition of
3 5i02 (20:35・45wt% ratio) to 0.05
~6.0wt%, semiconductor accelerator Nb:Os 0.02
~3.0wt%, grain boundary depletion layer forming agent S r (Cu l
/2W+/2) 0.05 to 6.0 wt% of 03 was added, and after mixing, it was calcined at 900°C. After wet grinding, it was dried, granulated, molded, and heated to 1400°C in the atmosphere. After sintering and wet grinding again, it is made into a paste using a resin and an organic solvent, and printed alternately with platinum paste for electrodes.
After hydrogen reduction at 300° C. and application of bismuth oxide, heat treatment was performed at 950° C. in the air, electrodes were adjusted, and electrical properties were measured. The measurement results are shown in Table 1. In addition, the sintering accelerator TiO2Al2O35i02 (20:35:45wt
% ratio) is commercially available T i 02. A I2O3,S
The powder of i02 was weighed and mixed at a weight ratio of 20:35:45, calcined at 1200°C, and pulverized.

Furthermore, grain boundary depletion layer forming agent 5r(CO13Ta23)O3
Mix commercially available SrCO3, Coo, Ta205,
It was obtained by calcining at 900°C and pulverizing.

(Left below) Table 1 As is clear from Table 1, the sintering accelerator T i 02-A I203S i O: 0.1 to 5 is added to 5rT103.
．． 0wt%, semiconductor accelerator Nb, O3 or 0.05-2
゜0wt%, grain boundary depletion layer forming agent 5r (C.

Ta23) This material obtained by adding 0.1 to 5.0 wt% of O3 and firing it exhibits extremely excellent dielectric properties and can be used as a capacitor. That is, as a result of microscopic observation,
The fine particles of the sintered body have a uniform particle size of 2.0 to 4.
At 0 μm, dielectric loss is less than 10% and apparent dielectric constant is 2.
．． It was over 000. Other measurements were taken of the temperature coefficient of capacitance, insulation resistance, boosted breakdown voltage 9 equivalent series resistance, etc., and satisfactory values were obtained. Note that if the sintering accelerator exceeds 5%, the sintered bodies will deform and adhere to each other, making it impractical.

FIG. 1 shows a grain boundary insulated semiconductor ceramic capacitor according to a first embodiment of the present invention. In FIG. 1, 11 is a grain boundary insulated semiconductor ceramic, 12 is an electrode, and 13 is a lead wire.

(Example 2) T 102-Mg0-8 I02 system (for example, 30:30:40 wt% ratio), Tie:Mn0 was added to commercially available industrial strontium titanate (SrTiO3).
-5i02 series (e.g. 10:50:40wt% ratio),
CaO-Mg0-A I2O3-3i O2 system (e.g. 30:10:15:45wt% ratio), Ti
02-A 1203-S i 02 series (e.g. 20
35:45wt% ratio), Zn0-Nb::05-8i
02 series (e.g. 50:45:5wt% ratio), 2102
M n OS i 02 series (e.g. 10:55:35w
0.05~6.0w of sintering accelerator selected from
t%, 0.4 wt% of semiconductor accelerator Nb2O5, grain boundary depletion layer forming agent S r (Co +, 3T a 2.,'
3) After adding 2.0 wt% of 03 and mixing well,
It was calcined at 900°C. After wet pulverization, drying, granulation, and molding are carried out in a reducing atmosphere consisting of 95% nitrogen and 5% hydrogen.
It was fired at 380°C, coated with bismuth oxide, and then heat-treated at 950°C in the atmosphere to form electrodes and measure electrical properties. The measurement results are shown in Table 2.

Note that the sintering accelerator is, for example, TiO2-MgO-8iO
2 system (30: 30: 40 wt% ratio) is commercially available T
i O2, MgO, S i 02 powder 3030:
Weighed and mixed at a weight ratio of 40, calcined at 1200°C,
Obtained by crushing. Furthermore, the grain boundary depletion layer forming agent is commercially available S
It was obtained by mixing rcO3, Coo, and Ta2O5, calcining at 900°C, and pulverizing.

(Left below) As is clear from Table 2, SrTiO3 has Tio:
-MgO-5io: sintering accelerator or 0.1 to 5.
0wt%, semiconductor accelerator Nb:! 05 or 0.4
This material obtained by adding 2.0 wt % of the grain boundary depletion layer forming agent and firing the material exhibits extremely excellent dielectric properties and can be used as a capacitor. That is, as a result of microscopic observation, the fine particles of the sintered body have a uniform particle size of 2.0 to 4.0 μm for each composition, and the dielectric loss is 1.0% or less.
The apparent dielectric constant was 2,000 or more. Other measurements were taken of the temperature coefficient of capacitance, insulation resistance, boosted breakdown voltage 1 equivalent series resistance, etc., and satisfactory values were obtained. Incidentally, if the sintering accelerator exceeds 5%, the sintered bodies deform and adhere to each other, making it impractical.

(Example 3) TiO2-MgO-3iO2 was added to commercially available industrial strontium titanate (SrTiO3).
3.0 wt % of the sintering accelerator (for example, 30:30:40 wt % ratio) and 0.5 wt % of the semiconductor accelerator Nb2O5.
%, grain boundary depletion layer forming agent S ro8B ao, + Ca
.

(C013T a2.3) 03. S ro, 4
B ao, 3Cao, 3(CO+:]Ta23)O3
After adding 0.05 to 6.0 wt% of and mixing well,
It was calcined at 900°C. After wet pulverization, drying, granulation, and molding are carried out in a reducing atmosphere consisting of 95% nitrogen and 5% hydrogen.
It was fired at 380°C, coated with bismuth oxide, and then heat-treated at 950°C in the atmosphere to form electrodes and measure electrical properties. The measurement results are shown in Table 3. The sintering accelerator is, for example, TiO2-MgO-SiO2 (30:30
:4C1wt% ratio) is commercially available TiQ2M・go,
5io2 powders were weighed and mixed at a weight ratio of 30:30:40, calcined at 1200°C, and pulverized.

Furthermore, grain boundary depletion layer forming agents are commercially available SrCO3, BaC
O2, CaCO5, Coo.

Ta205 was mixed, calcined at 900°C, and pulverized.

Table 3 (margin below) As is clear from Table 3, T in S r Ti O3
io2-MgO-8io: sintering accelerator 3.0
This material, which is obtained by adding 0.5 wt% of the semiconductor accelerator Nb2O5 and 0.1 to 5.0 wt% of the grain boundary depletion layer forming agent and firing, exhibits excellent dielectric properties and is used as a capacitor. can. That is, as a result of microscopic observation, the fine particles of the sintered body have a uniform particle size of 2 to 3 depending on the composition.
μm, dielectric loss is 1.0% or less, apparent permittivity is 2
．． It was over 000. Other temperature coefficient of capacitance, insulation resistance.

The boosted breakdown voltage, 2 equivalent wave train resistance, etc. were measured and satisfactory values were obtained. Note that if the sintering accelerator exceeds 5%, the sintered bodies will deform and adhere to each other, making it impractical.

Effects of the Invention As described above, according to the present invention, 0.1 to 5.0 wt% of a sintering accelerating additive is added to a perovskite-type oxide whose main component is strontium titanate (SrTiO3). 0.05 to 2.0 wt% of agent Nb2O,
and S r + −x−y B a x Ca y (
COl 3T a23) 03 (However, X≦0.3
．． After adding 0.1 to 5.0 wt% of a grain boundary depletion layer forming agent consisting of y≦0.3.0≦) (+y≦0.6), mixing and pressure molding, in a reducing atmosphere containing hydrogen. 1250-15
Bismuth oxide (
By applying a grain boundary diffusion substance containing Bi:03) and performing heat treatment at 850 to 1200°C in an oxidizing atmosphere to form an electrode,
Sr+-1-vB axCay (C01/3T a
Near 3) 03 (However, X≦0.3.y≦0.3
．． 0≦x+y≦0.6)
．． 1 to 5.0 wt% reaction/solid solution, then 0.1 to 5.0 wt% of the sintering accelerating additive and 0.05 to 2.0 wt% of the semiconducting accelerating additive Nb20s. After mixing and pressure molding, it is fired at 1250 to 1500°C in a reducing atmosphere containing hydrogen, a grain boundary diffusion substance containing Bi2O3 is applied to the surface of the fired product, and it is heated to 850 to 1200°C in an oxidizing atmosphere. By applying heat treatment to form an electrode, or by adding 0.1% of a sintering accelerating additive to a perovskite-type oxide whose main component is 5rTiO3.
~5.0 wt%, and 0.0 wt% of Nb2O5, an additive for promoting semiconductor formation.
05-2.0 wt%, and 5rt-1-yB axC
ay (C01,/3Ta:3)O3 (However, x
≦0.3. y≦0.3.0≦x+y≦0.6) Adding 0.1 to 5.0 wt% of a grain boundary depletion layer forming agent,
After mixing and pressure molding, 1250 to 150
Calcined at 0°C, then heated to 850°C in a reducing atmosphere containing hydrogen.
After reduction at 1400℃, Bi2O3 is deposited on the surface of the sintered body.
850-1 in an oxidizing atmosphere.
By applying heat treatment at 200°C to form electrodes,
The effect is that a grain boundary insulated semiconductor ceramic capacitor with good characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a grain boundary insulated semiconductor ceramic capacitor according to an embodiment of the present invention. 11... Grain boundary insulation type semiconductor ceramics, 12
... Electrode, 13 ... Lead wire. Ceramics 12...Kole 13 Sword edge

Claims (5)

[Claims] (1) A perovskite type oxide whose main component is strontium titanate (SrTiO_3), 0.1 to 5.0 wt% of a sintering accelerating additive, and a semiconductor accelerating additive Nb_2
0.05 to 2.0 wt% O_5 and Sr_1_-
____−_yBa_xCa_y(Co_1_/_3Ta
_2_/_3)O_3 (However, x≦0.3, y≦0.
3. Add 0.1 to 5.0 wt% of a grain boundary depletion layer forming agent consisting of 0≦x+y≦0.6), mix and pressure mold, and then at 1250 to 1500°C in a reducing atmosphere containing hydrogen. Bismuth oxide (Bi_2O_
3) is coated with a grain boundary diffusion substance containing 850%
A grain boundary insulated semiconductor ceramic capacitor whose electrodes are formed by heat treatment at ~1200°C. (2) The sintering accelerator additive is TiO_2-MgO-SiO_
2 system, TiO_2-MnO-SiO_2 system, CaO-M
gO-Al_2O_3-SiO_2 system, TiO_2-A
l_2O_3-SiO_2 system, ZnO-Nb_2O_5
The grain boundary insulated semiconductor ceramic capacitor according to claim 1, comprising a mixture selected from -SiO_2 series and ZrO_2-MnO-SiO_2 series. (3) Sr_1_-_x_-_yBa_xCa is added to the perovskite-type oxide mainly composed of SrTiO_3.
_y(Co_1_/_3Ta_2_/_3)O_3 (however, x≦0.3, y≦0.3, 0≦x+y≦0.6)
0.1 to 5.0 wt% of the grain boundary depletion layer forming agent is reacted and dissolved in solid solution, and then 0.1 wt% of the sintering accelerating additive is added.
~5.0 wt% and 0.05 to 2.0 wt% of the semiconducting accelerator Nb_2O_5 are added, mixed and pressure molded, and then fired at 1250 to 1500°C in a reducing atmosphere containing hydrogen to obtain the fired product. A grain boundary insulated semiconductor ceramic capacitor is formed by applying a grain boundary diffusion substance containing Bi_2O_3 to the surface of the capacitor and heat-treating the surface at 850 to 1200°C in an oxidizing atmosphere to form electrodes. (4) Add 0.1 to 5.0 wt% of the sintering accelerator additive and 0.05 to 2.0 w of the semiconducting accelerator Nb_2O_5 to the perovskite oxide whose main component is SrTiO_3.
t%, and Sr_1_−_x_−_yBa_xCa_
0.1 to 5.0 wt% addition of grain boundary depletion layer forming agent consisting of y(Co_1_/_3Ta_2_/_3)O_3 (x≦0.3, y≦0.3, 0≦x+y≦0.6) After mixing and pressure molding, it is heated to 1250 to 15
Calcined at 00°C and then heated at 850°C in a reducing atmosphere containing hydrogen.
After reduction at ~1400℃, Bi_2 is added to the surface of the sintered body.
A grain boundary diffusion substance containing O_3 is applied and 85% is applied in an oxidizing atmosphere.
A grain boundary insulated semiconductor ceramic capacitor whose electrodes are formed by heat treatment at 0 to 1200°C. (5) Add 0.1 to 5.0 wt % of a sintering accelerator additive and 0.05 to 2.0 w of a semiconductor accelerator additive Nb_2O_5 to a perovskite oxide whose main component is SrTiO_3.
t%, and Sr_1_−_x_−_yBa_xCa_
0.1 to 5.0 wt% addition of grain boundary depletion layer forming agent consisting of y(Co_1_/_3Ta_2_/_3)O_3 (x≦0.3, y≦0.3, 0≦x+y≦0.6) mixed and made into a paste, and printed/printed alternately with the electrode paste.
After molding, it is fired in advance at 1250 to 1500°C in the air, and then at 850 to 1400°C in a reducing atmosphere containing hydrogen.
After reducing the sintered body in
A grain boundary insulated semiconductor ceramic capacitor heat-treated at ℃.