JPH04112515A - 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(Co1/2Mo1/2)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 od its baked substance is coated with a grain-boundary diffusion 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 Nb2O5 and TiO2Al2O
Copper oxide (CuO) and bismuth oxide (Bi203) are diffused into the grain boundaries of a polycrystalline ceramic semiconductor obtained by adding a 35i02-based mixture, molding, and sintering to form a depletion layer at the grain boundaries. In a grain boundary insulated semiconductor capacitor obtained by insulating the grain boundaries and forming electrodes, the boost breakdown voltage is 12
00 V/IWl, Absolute R resistance approximately 1 x 10'MΩ/cT
Effective dielectric constant of 20.00 while maintaining insulation properties of 11.
Large values such as 0 to 100.000 are obtained.

Here, to describe the role of the diffusion substances Cub and Bi2O3, CuO forms an electron trap center at the grain boundaries of the sintered body, and CuO forms an electron trap center within the crystal grains of the n-type semiconductor crystal. It functions to trap electrons existing near the grain boundaries and 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 is ZrO
It is known as a good conductor of oxygen along with 2nd grade, exists in the grain boundaries and transports oxygen from the outside to the inside of the sintered body by diffusion.
It functions to supply oxygen necessary for grain boundary depletion layer formation.

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. Bi=03. The process involves diffusing CuO, etc. into the interior of the sintered body, but since the electrode spacing of laminated ceramics becomes narrower, the grain size of the sintered body must be suppressed, and the conventional Elements fabricated using this method are less likely to diffuse CuQ etc. than Bi2O3 etc. during the process, so characteristics tend to vary, and if the device is thick, copper oxide etc. must be sufficiently diffused into the interior. Because it is difficult to
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 objective is to obtain large elements with good characteristics simply by performing heat treatment and diffusion in air.

Means for Solving the Problems 1.3 In order to solve the problems, the present invention provides a perovskite type oxide mainly composed of SrT with 0.1 to 5.3 wt% of a sintering accelerating additive to make it a semiconductor. Accelerator additive Nb2
O5 from 0.05 to 2, Ovt%, and S r +−x
-yB axCa y (CO+, 2M O+/2)
03 (However, X≦0.3.y≦0.3,0≦)(+
y≦0.6) in a range of 0.1 to 5.
After adding 0 wt%, mixing, printing and molding, sintering at high temperature to make a semiconductor, 850 to 1200 °C in an oxidizing atmosphere.
A grain boundary insulated semiconductor ceramic capacitor is obtained by performing a diffusion treatment of bismuth oxide or the like.

Effect With this configuration, the perovskite-type oxide mainly composed of SrTiOx and the grain boundary depletion layer forming agent S r −
X-yB aXCay (Co +2Pv1 o +
2) Oj and the semiconductor-promoting additive Nb2O5 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 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,
An excellent grain boundary insulated semiconductor ceramic capacitor can be easily obtained 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 tables and drawings.

(Example 1) Titanyl strontium oxalate (SrTiO(C204)
Strontium titanate (S r Ties ) obtained by thermally decomposing sintering accelerator T i 02-
A 1203-31o2 (20: 35: 45wt
% ratio) from 0.05 to 6.0 wt%, semiconductor accelerator Nb
2O5 from 0.02 to 3. C) wt%, grain boundary depletion layer forming agent S r (COl/2M O+/2) 03 is 0.0
After adding 5 to 6.0 wt% and mixing well, heat at 900°C.
It was calcined at After wet grinding, drying, granulation, and molding,
Sintered at 1400℃ in the atmosphere, wet-pulverized again, made into a paste using resin and organic solvent, printed alternately with platinum paste for electrodes, hydrogen reduced at 1300℃, and coated with bismuth oxide. Heat treated at 950°C in air,
The electrodes were adjusted and their electrical properties were measured. The measurement results are shown in Table 1. In addition, the sintering accelerator TiO2-A1203-8i
02 (20:35:45wt% ratio) is commercially available T10
2. AI 203. 20 powder of S l 02
: Weighed and mixed at a weight ratio of 35 : 45, 120
It was obtained by calcining at 0°C and pulverizing. Furthermore, the grain boundary depletion layer forming agent Sr(co12MO+2)03 is commercially available SrCO3
, COO, and MOO3 were mixed, calcined at 900°C, and pulverized.

(Left below) Table 1 As is clear from Table 1, sintering accelerator T i 02-A I2O38i O= Kao, 1 to 5.0 wt%, promotes semiconducting to S r T l O: + Agent Nb2O5 is 0
．． 05 to 2.0 wt%, grain boundary depletion layer forming agent Sr(Co,
,.

M Ol/2) 03 is 0.1 to 5. This material obtained by firing with Owt% added saponide 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.
~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.

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-3i 02 was added to commercially available industrial strontium titanate (SrTi03).
system (e.g. 30:30:40wt% ratio), TiO2Mn
0-5i02 series (e.g. 10:50:40wt% ratio)
, CaO-Mg0-A I2O3-S iO: system (e.g. 30:10.15.45 wt% ratio), T i 0
2-A +203-3 i 02 series (e.g. 2035:
45wt% ratio), Zn0-Nb:0s-8iO: system (e.g. 50:45:5wt% ratio), Zr02Mn0
- 0.05 to 5.0 wt% of a sintering accelerator selected from the 3in2 system (for example, 10:55:35 wt% ratio), 0.4 wt% of the semiconductor accelerator N b 20 s, grain boundary depletion layer formation Agent S r (COl/2M Ol/2) 03 to 2
．． After adding 0 wt% and mixing well, it was calcined at 900°C. After wet grinding, drying, granulation, molding, and nitrogen 9
It was fired at 1380° C. in a reducing atmosphere consisting of 5% hydrogen and 5% hydrogen, coated with bismuth oxide, and then heat treated at 950° C. in the air to form electrodes and measure electrical properties. The measurement results are shown in Table 2.

Note that the sintering accelerator is, for example, Tie: -MgO3i
02 series (30/30/40wt% ratio) is commercially available Ti
O=, MgO, Si O2 powder 30 + 30
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 MOO:i, calcining at 900°C, and pulverizing.

(Left below) As is clear from Table 2, Tio=
-MgO-3io: sintering accelerator of 0, 1 to 5.
0wt%, semiconductor accelerator Nb=05 or 0.4wt%5
The 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. 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. In addition, the temperature coefficient of capacitance, insulation resistance, boosted breakdown voltage, 7 equivalent series 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.

(Example 3) Tio2-MgO-3io2 system (
For example, add a sintering accelerator (30:30:40wt% ratio) to 3.
0wt%, semiconductor accelerator Nb: Os is Q, 5w
t%, grain boundary depletion layer forming agent S ro, s B ao, +
Cao, +(C01.MO+ 2)O: ], S
ro, +B ao, 3Cao, 3(Co + :M
o +2) 0.05 to 5.0 wt% of 03 was added, mixed well, and then calcined at 900°C. After wet pulverization, it is dried, granulated, 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 an electrode. was formed and the electrical properties were measured. The measurement results are shown in Table 3.

Incidentally, the sintering accelerator is, for example, t! fT i 02-M g
O-S i 02 system (30:30/40wt% ratio) is a mixture of commercially available TiO2MgO, SiO2 powder at 30/30%
: They were weighed and mixed at a weight ratio of 40, calcined at 1200°C, and pulverized. Further, grain boundary depletion layer forming agents include commercially available SrCO:i, BaCO3, CaC0:+, Co
o.

It was obtained by mixing MoO3, calcining at 900°C, and pulverizing.

(Margin below) As is clear from Table 3, SrTiO: +l
Sintering accelerator power such as o2-MgO-3i02\3,0w
t%, a semiconductor accelerator Nb: 0.5wt%, and a grain boundary depletion layer forming agent 0.1-5.0wt% were added and fired. This material exhibits excellent dielectric properties and is suitable for use in capacitors. Can be used as That is, as a result of microscopic observation, the fine particles of the sintered body have a particle size force (well aligned and 2 to 3
In μm, the dielectric loss was 1.0% or less, and the apparent dielectric constant was 2.000 or more. Other capacitance temperature coefficients,
Insulation resistance boost breakdown voltage 1 equivalent series 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 Nb2O5,
and Srl-x-y B a x Ca y (Co
l:M O+ :) 03 (However, X≦03.y≦
After adding 0.1 to 5.3 wt% of a grain boundary depletion layer forming agent consisting of 0.3.0≦X+y≦0.6), mixing and pressure molding, the mixture was heated at 1250 to 1500°C in a reducing atmosphere containing hydrogen. Bismuth oxide (Bi20
3) is coated with a grain boundary diffusion substance containing 850%
By performing a heat treatment at ~1200°C to form an electrode, or, although no examples are shown, SrTiO:
The perovskite type oxide whose main component is + is pre-filled with Sr.
l-1-A B axCa, (Col/:'Mo12:)
03 (However, X≦0.3.y≦0.3.0≦X+
y≦0.6) in a range of 0.1 to 5.
Owt% reaction/solid solution, then 0.1 to 5.0wt% of the sintering accelerating additive, Nb, the semiconductor accelerating additive.
After adding 0.05 to 2.0 wt% of 2O5, mixing and pressure molding, 1250 to 150% of 2O5 was added in a reducing atmosphere containing hydrogen.
It is fired at 0°C, a grain boundary diffusion substance containing Bi2O3 is applied to the surface of the fired product, and the
By performing heat treatment at ℃ to form an electrode, or by adding 0.1 to 5.0 wt% of a sintering accelerating additive to a perovskite type oxide whose main component is SrTiO:+.
, 0.05 to 2.0% of the semiconductor conversion promoting additive. Out%, and Sr+−x−yB a xCay(Co, 2M
o,・2)03 (However, X≦0.3゜y≦0.3.0
≦)(+y≦0.6).
After adding 1 to 5.0 wt%, mixing and pressure molding, the sintered body was pre-fired at 1250 to 1500°C in the air, and then reduced at 850 to 1400°C in a reducing atmosphere containing hydrogen. A grain boundary insulated semiconductor ceramic capacitor with good characteristics can be obtained by applying a grain boundary diffusion substance containing Bi:O:+ to the surface and performing heat treatment at 850 to 1200°C in an oxidizing atmosphere to form an electrode. You can get the effect that you can.

[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. Figure 1

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_/_2Mo
_1_/_2)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_/_2Mo_1_/_2)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_
Adding 0.1 to 5.0 wt% of grain boundary depletion layer forming agent consisting of y(Co_1_/_2Mo_1_/_2)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_
Adding 0.1 to 5.0 wt% of grain boundary depletion layer forming agent consisting of y(Co_1_/_2Mo_1_/_2)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 ℃.