JPH04112517A - 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 baked 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(Co1/2W1/2)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 grain boundary insulated semiconductor ceramic capacitors, and more particularly to laminated grain boundary insulated semiconductor ceramic capacitors.

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 N b 205 and TiO2-A
Copper oxide (CuO) and bismuth oxide (Bi203) are diffused into the grain boundaries of a polycrystalline ceramic semiconductor formed by adding an l2O3SiO2-based mixture, molding and sintering, and forming a depletion layer at the front grain boundary. However, in the grain boundary insulated semiconductor capacitor obtained by insulating the grain boundaries and forming electrodes, the boost breakdown voltage is 1200 V/image, and the insulation resistance is approximately I x 10'MΩ/
effective dielectric constant of 20.00 while maintaining the insulation properties of am
Large values such as 0 to 100.000 are obtained.

Here, to describe the role of the diffusion substances Cub and BizO:+, CuO forms an electron trap center in the grain boundaries of the sintered body, and forms an electron trap center in the crystal grains of the n-type semiconductor crystal. , traps the electrons present near the grain boundaries and functions to form a depletion layer where no electrons exist 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 is Z
It is known as a good conductor of oxygen along with r02 etc.
It exists in the grain boundaries and transports oxygen from the outside to the inside of the sintered body by diffusion, and functions to supply the oxygen necessary for the formation of grain boundary depletion layers.

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 bismuth oxide containing copper oxide in the form of bismuth oxide and applying it around the sintered body obtained by firing at high temperature, followed by heat treatment. However, because the spacing between the electrodes of laminated ceramics becomes narrower, the grain size of the sintered body must be suppressed, and elements manufactured using conventional methods Compared to Bi2O3, etc., CuO does not easily diffuse <<, which causes variations in properties (furthermore, if the material is thick, it is difficult to diffuse copper oxide etc. into the interior),
There were problems such as restrictions on the size of the element.

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 purpose is to obtain large devices with good characteristics simply by heat-treating and diffusing them 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 5rTiO:r, and a sintering promoting additive of 0.1 to 5.3 wt% to promote semiconductor formation. Additive Nb2
0.05 to 2.0 wt% O5, and S r +−x
-yB a XCa y (Co +, zW+.) 0
3 (However, X≦0.3.y≦0.3.0≦x+y≦0
．． 6) 0.1 to 5.0 wt of grain boundary depletion layer forming agent consisting of
%, mixed, printed, molded, fired at high temperature to become a semiconductor, and then subjected to 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. .

Effect With this configuration, the perovskite type oxide mainly composed of SrTiO3 and the grain boundary depletion layer forming agent S r 1
-1-y B a x Ca y (Co1/ 2W+
2) 03 and the semiconductor-promoting additive N b 205 are reacted and dissolved in solid solution, and during the cooling process during firing, oxides containing copper are precipitated at the grain boundaries, and the bismuth oxide diffused at the grain boundaries is The oxygen that diffuses and reaches grain boundary materials such as copper are further oxidized, forming electron trap centers at the grain boundaries, and a depletion layer is created along the grain boundaries within the low-resistance semiconductor crystal formed by reduction. form. The depletion layer obtained in this way has good insulating properties, and charges are stored on both sides of the depletion layer, resulting in a high-quality capacitor. That is, according to the present invention, it is possible to easily obtain an excellent grain boundary insulated semiconductor ceramic capacitor without requiring the conventional process of applying and diffusing CuO or the like after semiconductor formation.

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 TiO2-Al2O2 is added to strontium titanate (SrTiO3) obtained by thermal decomposition of
-3in2 (20:35:45wt% ratio) from 0.05 to
6.0 wt%, semiconductor accelerator N b 205 0.0
2-3. Oat%, grain boundary depletion layer forming agent S r (Cu
l-2Wl-2) 03 was added in an amount of 0.05 to 6.0 wt%, mixed well, and then calcined at 900°C. After wet pulverization, drying, granulation 7 molding, sintering at 1400 ° C. in the atmosphere, wet pulverization again, paste using resin and organic solvent, printing alternately with platinum paste for electrodes,
After hydrogen reduction at 1300° 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 TiO2-A1203--SiO2 (20:35:
45 wt% ratio) is commercially available TiO□, Al 203
．． The powder of S i 02 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 Sr (CO+.Wl.)
03 was obtained by mixing commercially available SrCO3, Coo, and WO2, calcining the mixture at 1000°C, and pulverizing it.

(Margins below) Table 1 As is clear from Table 1, the sintering accelerator Ti02-A I20:+-SiO2 was added to 5rTiO:+ by 0.1.
~5.0 wt%, semiconductor accelerator Nb2O5 is 0.05
~2.0wt%, grain boundary depletion layer forming agent Sr (Cot 2
This material obtained by adding 0.1 to 5.0 wt% of W1°)03 and firing it exhibits extremely excellent dielectric properties and can be used as a capacitor. That is, as a result of microscopic observation, the particle size of the fine particles of the sintered body was well aligned, ranging from 2.0 to 4.0μ.
m, dielectric loss is 1.0% or less, and apparent permittivity 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, 1) indicates a grain boundary insulated semiconductor ceramic, 12 an electrode, and 13 a lead wire.

(Example 2) T i O□M g OS i 0 was added to commercially available industrial strontium titanate (SrTiO3).
2 system (e.g. 30:30:40wt% ratio), TiO2M
n0-8i02 series (e.g. 10:50:40wt% ratio)
, Cao MgOA 1203 S i O2 system (e.g. 30:10:15:45wt% ratio)
, T i 02 A l 203 S i O2 system (e.g. 2035:45wt% ratio), ZnONb:Os
S i O2 system (for example, 50:5 wt% ratio), Z r O2Mn0-8iOz system (for example, 10:5 wt% ratio),
0.0 sintering accelerator selected from 55:35wt% ratio)
5 to 5.0 wt%, and 0.4 of Nb2O5 as a semiconductor accelerator
wt%, grain boundary depletion layer forming agent S r (CO+/2W+z
2) 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-MgOSiO2
The system (80:30/40wt% ratio) was commercially available T i 0
2. MgO, Si02 powder at 30:30:40
They were weighed and mixed at a weight ratio of , calcined at 1200°C, and pulverized. Furthermore, the grain boundary depletion layer forming agent is commercially available S r
It was obtained by mixing CO3, CoO, and WO3, calcining at 1000°C, and pulverizing.

(Left below) Table 2 As is clear from Table 2, SrTiO3 has TiO3-
Sintering accelerator such as MgO-SiO2 is 0, 1~5.0w
t%, semiconductor accelerator N b 205 or 0.4wt%1
This material obtained by adding 2.0 wt % of grain boundary depletion layer forming agent and firing exhibits extremely excellent dielectric properties and can be used as a capacitor. In other words, as a result of microscopic observation, the particle size of the fine particles of the sintered body was well matched depending on the composition.
~4.0 μm, the dielectric loss was 1.0% or less, and 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. Note that if the sintering accelerator exceeds 5%, the sintered bodies will deform and adhere to each other, making it impractical.

(Example 3) T i 02-Mg0-S i 0 was added to commercially available industrial strontium titanate (SrTiO3).
3.0 wt% of the sintering accelerator of 2 systems (for example, 30:30:40 wt% ratio), and Q of the semiconductor accelerator N b 20 s.
, 5wt%, grain boundary depletion layer forming agent S ro, 8 B ao
, l Ca.

(CO+ 2W+ 2) 03. S r
o, <B ao, 3c ao, 3(C012W1.'2
)03 to 0.05 to 6. After adding Qwt% and mixing well, it was calcined at 900°C. After wet grinding, drying
Granulated and molded, fired at 1380°C in a reducing atmosphere consisting of 95% nitrogen and 5% hydrogen, coated with bismuth oxide, and then heat treated at 950°C in the air to form electrodes and measure electrical properties. did. The measurement results are shown in Table 3. Note that the sintering accelerator is, for example, T 102-Mg0-3 i02 series (
30:30:40wt% ratio) is commercially available TiO2
The powders of MgO and SiO2 were weighed and mixed at a weight ratio of 30.times.3040, calcined at 1200.degree. C., and pulverized. Furthermore, the grain boundary depletion layer forming agent is commercially available SrCO3, BaCO
3, CaC0:+, Cod.

W O3 was mixed, calcined at 900°C, and pulverized.

Table 3 (margin below) As is clear from Table 3, T 102 in 5rTjO3
-3.0wt of sintering accelerator with Mg0-3 i O2
%, a semiconductor accelerator Nb2O5 or 0.5 wt% grain boundary depletion layer forming agent is added in an amount of 0.1 to 5.0 wt%, and the material obtained by firing exhibits excellent dielectric properties and can be used as a capacitor. In other words, as a result of microscopic observation, the fine particles of the sintered body have a particle size of 2 to 3 μm depending on the composition, the dielectric loss is less than 1.0%, and the apparent dielectric constant is 2.00.
It was 0 or more. Other measurements such as temperature coefficient of capacitance, insulation resistance, boosted breakdown voltage, and equivalent series resistance were obtained, 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). The agent Nb2O5 was 0.05~2. Ovt%
, and S r +−x−y B a x Ca y (
Cot: W+ = ) Owl (Tatashi, 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≦z+y≦0.6), mixing and pressure molding, 1250 to 1000 g in a reducing atmosphere containing hydrogen. 1
By firing at 500°C, applying a grain boundary diffusion substance containing bismuth oxide (Bi::03) on the surface of the fired product, and performing heat treatment at 850 to 1200°C in an oxidizing atmosphere to form an electrode, Alternatively, although no examples were shown,
3 rH-x-yB aXc ay (Co,
2W+ -)03 (Tap, X≦0.3.y≦0.
3.0≦x+y≦0.6), the grain boundary depletion layer forming agent is 0.1 to 5. Qwt% reaction/solid solution, then 0.1 to 5.0 wt% of the sintering accelerator additive and 0.05 to 2.0 wt% of the semiconductor formation accelerating additive Nb2O5. Qwt% added,
After mixing and pressure molding, 12% in a reducing atmosphere containing hydrogen.
It is fired at 50 to 1500°C, and Bi is added to the surface of the fired product.
A grain boundary diffusion substance containing 2O3 is applied and 85% is applied in an oxidizing atmosphere.
By heat-treating at 0 to 1200°C to form an electrode, or by adding 0.1 to 0.1 to 0.1 to 0.1 to 0.1 sintering accelerating additive to a perovskite type oxide whose main component is 5rTiO,+.
5.0wt%, semiconducting accelerating additive 0.05~2.0
wt%, and S r I-x-yB a,,ca
A grain boundary depletion layer forming agent consisting of y(Co 1.z'2 W+/2) 03 (where X≦0.3゜y≦0.3.O≦z+y≦0.6) is used in an amount of 0.1 to 5 After adding .0wt%, mixing and pressure molding,
Calcined at 00°C and then heated at 850°C in a reducing atmosphere containing hydrogen.
After reduction at ~1400℃, Bi2O is deposited on the surface of the sintered body.
850~ in an oxidizing atmosphere.
By performing a heat treatment at 1200° C. to form an electrode, it is possible to obtain a grain boundary insulated semiconductor ceramic capacitor with layer characteristics.

[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. 1) Grain boundary insulation type semiconductor ceramics, 12
... Electrode, 13 ... Lead wire. ℃33x12...Electrode 13/Lead wire

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_-
_x_−_yBa_xCa_y(Co_1_/_2W_
1_/_2)O_3 (however, x≦0.3, y≦0.3
, 0≦x+y≦0.6).
．． After adding 1 to 5.0 wt%, mixing and pressure molding,
It is fired at 1250-1500°C in a reducing atmosphere containing hydrogen, and bismuth oxide (Bi_2O_3) is deposited on the surface of the fired product.
) in an oxidizing atmosphere.
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(Cu_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 a sintering accelerator additive and 0.05 to 2.0 w of a semiconductor accelerator 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_/_2W_1_/_2)O_3 (x≦0.3, y≦0.3, 0≦x+y≦0.6) death,
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℃, Bi_2O is deposited on the surface of the sintered body.
A grain boundary diffusion substance containing _3 is applied, and 850
A grain boundary insulated semiconductor ceramic capacitor whose electrodes are formed by heat treatment at ~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_/_2W_1_/_2)O_3 (x≦0.3, y≦0.3, 0≦x+y≦0.6) death,
After mixing and forming a paste, printing and molding it alternately with the electrode paste, it is fired in advance at 1250 to 1500°C in the air, then reduced at 850 to 1400°C in a reducing atmosphere containing hydrogen, and then the sintered body is A grain boundary diffusion substance containing Bi_2O_3 is applied to the surface and heated at 850 to 1200°C in an oxidizing atmosphere.
A grain boundary insulated semiconductor ceramic capacitor that is heat treated.