JPH04112512A - 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(Mn2/3W1/3)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, 5rT103 is the main component, and Nb2O5 and Ti02-A
Copper oxide (M n
In a grain boundary insulated semiconductor capacitor obtained by diffusing O) and bismuth oxide (Bi203) to form a depletion layer at the grain boundaries, insulating the grain boundaries and forming electrodes, a boost breakdown voltage of 1200 V/order was obtained. , insulation resistance approximately I x 105
Effective permittivity of 20 while maintaining insulation properties of MΩ/cm
,000 to 100.000. 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, B 1203
It is known as a good conductor of oxygen along with ZrO2, etc., and exists at the grain boundaries, and functions to transport oxygen from the outside to the inside of the sintered body by diffusion, and to supply the oxygen necessary for forming 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, grain boundary insulated semiconductor ceramic capacitors obtained by such conventional manufacturing methods require making the crystal grains in the sintered body as large as possible in order to obtain large capacitance. Bi:03. is applied to the periphery of a sintered body obtained by firing a paste-like bismuth oxide containing copper oxide at a high temperature, followed by heat treatment. Does it go through a process of diffusing CuO etc. into the inside of the sintered body?
Since the electrode spacing of laminated ceramics becomes narrower, the grain size of the crystal grains of the sintered body must be suppressed, and elements manufactured by conventional methods do not contain Bi2O2 during the process.
CuO etc. are difficult to diffuse compared to other materials such as CuO, etc. Therefore, the characteristics tend to vary.Furthermore, if the device is thick, it is difficult to diffuse copper oxide etc. sufficiently into the inside, so it is difficult to diffuse copper oxide etc. There were issues such as limitations.

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 adds 0.1 to 5.9 wt% of a sintering promoting additive to a perovskite type oxide mainly composed of 5rTiO2. Agent Nb
20 s to 0.05 to 2.0 wt%, and S r 1
-x-yB axCay (Mn2z3W+/3) 0
3 (However, X≦o, s, y≦0.3, 0≦x+y≦
0.6) grain boundary depletion layer forming agent consisting of 0.1 to 5.0w
After adding t%, mixing, printing, and molding, sintering at high temperature,
After converting into a semiconductor, a grain boundary insulated semiconductor ceramic capacitor is obtained by performing a diffusion treatment of bismuth oxide or the like at 850 to 1200° C. in an oxidizing atmosphere.

Effect: With this configuration, the perovskite-type oxide mainly composed of 5rTiO3 and the grain boundary depletion layer forming agent S r +
−x−yB a xCa y′(M n =3W+,
) 03 and the semiconductor-promoting additive Nb2O are reacted and dissolved in solid solution, and during the cooling process during firing, copper-containing oxides are precipitated at the grain boundaries, and the bismuth oxide diffused at the grain boundaries is diffused. The oxygen that has reached this process further oxidizes grain boundary materials such as copper, forming electron trap centers at the grain boundaries, and forming depletion layers along the grain boundaries within the low-resistance semiconductor crystal formed by reduction. do. 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 TiO2Al2O35 is added to strontium titanate (SrTiO2) obtained by thermally decomposing 2.4H20).
i02C20:35:45it% ratio) from 0.05 to 6.
0 wt%, 0.02 to 3 of the semiconductor accelerator Nb2O5,
9 wt%, grain boundary depletion layer forming agent S r (CLl l/2
0.05 to 6.0 wt% of W+/2) 03 is added,
After mixing well, the mixture was calcined at 900°C. After wet pulverization, it is dried, granulated, molded, sintered at 1400°C in the air, wet pulverized again, made into a paste using a resin and an organic solvent, and printed alternately with platinum paste for electrodes. 130
After hydrogen reduction at 0° 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 T
1o2-A I203-S i 02 (20: 3
5.45wt% ratio) is commercially available T i 02. A 1
203. S i 02 powder 20 + 35:
They were weighed and mixed at a weight ratio of 45, calcined at 1200°C, and pulverized. Furthermore, grain boundary depletion layer forming agent S r (M
n = 3W +, = a ) 03 is commercially available S r
C03, M n C03, and WO3 were mixed, calcined at 900°C, and pulverized.

(Margins below) Table 1 As is clear from Table 1, the sintering accelerator TiO3-A I =033 i O: 0 is added to S r T i O2.
, 1 to 5.0 wt%, semiconductor accelerator Nb2O5 or 00
5 to 2.0 wt%, grain boundary depletion layer forming agent Sr (Mn23W
1: ]) This material obtained by adding 0.1 to 5.0 wt% of O0 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. In addition, the temperature coefficient of capacitance, 7 insulation resistance, 1 boosted breakdown voltage, and 1 equivalent series resistance were measured and satisfactory values were obtained. It should be noted that if the sintering accelerator content 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 i 02-MgO-9 was added to commercially available industrial strontium titanate (S, r T i 03).
i O2 system (e.g. 30:30:40wt% ratio), T
i O2Mn0-8i02 system (e.g. 10:50:40
wt% ratio), CaO-MgO-A1203-Sin: system (e.g. 30:10:15:45wt% ratio)
, T i 02-A 1203-S i 02 system (e.g. 2035:45wt% ratio), ZnO-Nb205-5
i02 series (e.g. 50:45:5wt% ratio), Zr
O.

0.05 to 5.0 wt% of a sintering accelerator selected from the Mn0-SiO2 system (for example, 10:55:35 wt% ratio);
0.4 wt% of semiconductor accelerator N b 205, grain boundary depletion layer forming agent S r (M n 2/3W +/3)
After adding 2 (1 wt%) of 03 and mixing well, 90
It was calcined at 0°C. After wet pulverization, drying, granulation, and molding are performed in a reducing atmosphere consisting of 95% nitrogen and 5% hydrogen.
After baking at 0℃ and applying bismuth oxide,
Heat treatment was performed at 50° C., electrodes were formed, and electrical properties were measured. The measurement results are shown in Table 2.

Note that the sintering accelerator is, for example, TiO2-MgO-810.
2 system (30: 30 = 40wt% ratio) is commercially available T
i O=, MgO, Si O2 powder 30304
They were weighed and mixed at a weight ratio of 0, calcined at 1200°C, and pulverized. Furthermore, the grain boundary depletion layer forming agent is commercially available S r
Mix C03, M n C03, WO3 and heat to 900℃
It was calcined and crushed.

(Left below) Table 2 It is clear from Table 2 that 5rTiOs has T 10
2-MgO-S i O: 0, 1 sintering accelerator
-5.0wt%, semiconductor accelerator Nb2O5 or 0.4w
This material obtained by adding 2.0 wt % of a 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 particle size of the fine particles of the sintered body was well matched for each composition, 2.0 to 4.0 μm, the dielectric loss was 1.0% or less, and the apparent dielectric constant was 22000 or more. Ta. Other measurements were taken of the temperature coefficient of capacitance, insulation resistance, boosted breakdown voltage 2 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) Ti02-MgO-5i02 was added to commercially available industrial strontium titanate (SrTiO3).
3.0 wt % of the sintering accelerator (for example, 30:30:40 wt % ratio) and 0.0 wt % of the semiconductor accelerator N b 20 s.
5 wt%, grain boundary depletion layer forming agent S ro, 8 B ao,
+Cao, +(M n2.・3W+/3) 03.
S r O4B ao, 2Cao 3(M n
2.3W 1%3) 03 to 0.05~6.0wt
% was added, mixed well, and then calcined at 900°C.

After wet pulverization, it is dried, granulated, molded, and fired at 1380°C in a reducing atmosphere consisting of 95% nitrogen and 5% hydrogen. After coating with bismuth oxide, it is heat-treated at 950°C in the air to form an electrode. The electrical properties were measured. The measurement results are shown in the third
Shown in the table. Note that the sintering accelerator is, for example, T i 02
M g OS i 02 series (30: 30: 40
wt% ratio) is commercially available T i O2M g O, S i
The powders of No. 02 were weighed and mixed at a weight ratio of 30:30:40, calcined at 1200°C, and pulverized. Furthermore, the grain boundary depletion layer forming agent is commercially available SrCO3, BaCO
3. Mix CaCO3, MnCO3WO3 and heat to 900℃
It was calcined and crushed.

Table 3 (margin below) As is clear from Table 3, 5rTiO2 has TiO3-
This material was obtained by adding 3.0 wt% of a sintering accelerator such as MgO-3io2, 0.5 wt% of a semiconductor accelerator Nb2O5, and 0.1 to 5.0 wt% of a grain boundary depletion layer forming agent and firing. exhibits 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 uniform for each composition and was 2 to 3 μm, the dielectric loss was 1.0% or less, and the apparent dielectric constant was 2.000 or more. Other measurements such as temperature coefficient of capacitance and insulation resistance boosted breakdown voltage 1 equivalent series resistance were obtained, and satisfactory values were obtained. Incidentally, if the sintering accelerator exceeds 5%, the sintered bodies deform and adhere to each other, making it impractical.

Effects of the Invention As described above, according to the present invention, a sintering accelerator additive is added to a perovskite-type oxide whose main component is strontium titanate (SrTiO3). Ovt% Semiconductorization promoting additive Nb: 05 to 02O5 to 2.0 wt%, and S r + -x-y B a x Ca y (N1
n 23W+ 3 )03 (Tap, X≦03.y
0.1 to 5.0 wt% of a grain boundary depletion layer forming agent consisting of 0.3, 0.03,0.0 The surface of the fired product is coated with bismuth oxide (Bi.0
3) is coated with a grain boundary diffusion substance containing 850%
By performing heat treatment at ~1200°C to form an electrode, or, although no examples are shown, 5rTiO2
The perovskite type oxide whose main component is Sr,
~, -7B axCay (Mn2:I
wi 3) 03 (pukotashi, X≦0.3.y≦0.3.0≦x+y≦0,6
0.1 to 5.0 wt % of a grain boundary depletion layer forming agent consisting of ) is reacted and dissolved in solid solution, and then 0.1 to 5.0 wt % of a sintering accelerating additive is added.
1 to 5.0 wt%, semiconducting accelerating additive Nb:05
．． After adding 05 to 2.0 wt%, mixing and pressure molding, it is fired at 1250 to 1500 °C in a reducing atmosphere containing hydrogen, and a grain boundary diffusion substance containing Bi2O3 is applied to the surface of the fired product, and oxidized. By performing heat treatment at 850 to 1200°C in an atmosphere to form an electrode, or by adding 0.1 to 5.0 wt% of a sintering accelerator additive to a perovskite type oxide whose main component is 5rTiO,+. 02O5 to 2.0 wt% of the semiconducting accelerating additive, and S r
+ -x-y B a x Cay(Mn2.z2 W
l/3) 03 (However, X≦0.3.y≦0.3
．． 0≦x+y≦0.6)
．． 1-5. After adding Oyt%, mixing and pressure molding,
After firing in advance at 1250 to 1500°C in the air and then reducing at 850 to 1400°C in a reducing atmosphere containing hydrogen, a grain boundary diffusion substance containing Bi2O3 is applied to the surface of the sintered body, and then fired in an oxidizing atmosphere. By performing heat treatment at 850 to 1200° C. to form electrodes, it is possible to obtain a grain boundary insulated semiconductor ceramic capacitor with layer characteristics.

[Brief explanation of the drawing]

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.

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(Mn_2_/_3W_
1_/_3)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 series, 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 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(Mn_2_/_3W_1_/_3)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(Mn_2_/_3W_1_/_3)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.