JPH0249404A - Composite functional element - Google Patents

Abstract

PURPOSE:To obtain a varistor suitable for low voltage by a method wherein high-speed noise is effectively absorbed by diffusing the glassy oxide such as Bi, Pb, Zn, Cu, Na, B, Si and the like into a crystal grain boundary. CONSTITUTION:A semiconductor porcelain is mainly composed of SrTiO3, and it contains at least a kind of 0.05 to 1wt.% selected from the group consisting of oxides such as a rare-earth element, Nb, W and Ta as a semiconductivity- giving agent. A glassy oxide is diffused into the crystal grain boundary of the semiconductor porcelain. A composite functional element is formed using the semiconductor porcelain. As a result, an excellent non-linear of voltage can be accomplished as in the state wherein the large electrostatic capacitance of an SrTiO3 semiconductor porcelain is being maintained. As a result, high speed noise can be absorbed effectively, and a varistor suitable for low voltage can also be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to a multi-functional device which has a 5rTIOs semiconductor ceramic as its main component and has a high resistance layer formed at its grain boundaries, and has a varistor function and a capacitor function. Regarding improvements.

[Conventional technology]

In recent years, micro combinators have been installed in various electronic devices, and in such cases, malfunction of the devices due to noise has become a major problem. Therefore,
Demand for varistors to absorb voltage noise is increasing.

Semiconductor ceramics with high resistance layers formed at grain boundaries are known as varistor materials, and conventionally, ZnO-based, StC
A 5rTIO type or a 5rTIO type is used.

[Technical problem to be solved by the invention] However,
ZnO-based varistors, which are being put into practical use, have excellent voltage nonlinearity, but have problems such as poor response to high-speed noise (and low effectiveness in absorbing static electricity noise, etc.).

On the other hand, with the SIC type, the voltage nonlinearity was not so good (there were cases where the noise voltage could not be absorbed completely).

Therefore, varistors based on 5rTiO are attracting attention. The most important feature of varistors using 5rTIO type semiconductor ceramics is that they have a large capacitance, which is nearly 10 times that of ZnO type semiconductor ceramics. Therefore,
It has excellent ability to absorb high-speed noise.

However, in terms of varistor characteristics, that is, voltage nonlinearity, 5rTiO semiconductor ceramics have about twice the performance as SIC semiconductor ceramics, but are considerably inferior to ZnO systems, at 1/2 to 115 times the performance. Therefore, the voltage suppressing effect is small, which has been a big problem when considering the use of 5rTIO-based semiconductor ceramics.

Further, the driving voltage of a microcomputer is approximately 3 to 5 cm, and currently there is no varistor that can handle this low voltage.Therefore, there is a demand for a varistor that can handle such a low voltage.

Therefore, an object of the present invention is to provide a high-speed noise absorption system with excellent absorption ability for high-speed noise;
Moreover, the voltage nonlinearity is also improved, and the desired varistor voltage can be easily obtained.
The object of the present invention is to provide an s-based multifunctional device.

(Means for Solving Technical Problems) The multifunctional device of the present invention has S r Ti Os as its main component, and a semiconductor agent selected from the group consisting of rare earth elements, Nb, W, and Ta oxides. The present invention is characterized in that it is constructed using semiconductor porcelain containing 0.05 to 1% by weight of at least one of the following, and in which glass oxide is diffused in the grain boundaries.

Among the above compositions, the one containing 0.05 to 1% by weight of at least one of the oxides of rare earth elements, Nb, W, and Ta forms a high-resistance layer at the grain boundaries of the 5rTiO-based porcelain. This is to make it into a semiconductor, and it has been used conventionally.

As the glass oxide used in the present invention, B tS
Glass oxides such as pb, Zn, Cu, Na, B, and S + can be mentioned.

[Operation and effects of the invention]

Conventionally, when producing semiconductor porcelain mainly composed of SrTiOs, Bl, Pb, Zn, Cu, Na5
By oxidizing and diffusing B, S, etc., 5rT
It has been known that varistors and capacitors in IO systems can be constructed.

Therefore, the inventors of the present application made intensive studies to obtain a multifunctional device with better voltage nonlinearity while taking advantage of the characteristics of the 5rTiO1-based semiconductor ceramic. The present inventors have discovered that a multifunctional device with superior voltage nonlinearity can be obtained by diffusing the oxidized oxide, leading to the present invention.

That is, according to the present invention, Bi, Pb, Z
Since glass oxides such as n, Cu, Na, B, and Sl are diffused, excellent voltage nonlinearity is achieved while maintaining the large capacitance of the 5rTIOs semiconductor ceramic. Therefore, it is possible to obtain a multifunctional device that can effectively absorb high-speed noise and also has an excellent voltage suppression effect. In addition, by adjusting the amount of diffusion of the glass oxide, it is easy to control the varistor voltage, and therefore it is easy to realize a varistor compatible with low voltages.

[Explanation of Examples]

5rCO, and T f O* are blended in a ratio to obtain 5rTIOz, and Y2O, as a semiconducting agent, accounts for 0.0% of the total weight.
A mixture of 0.05% by weight was prepared. The mixture thus prepared was heated to 1000°C to 1200°C.
The mixture was precalcined at a temperature of about 3 hours and then ground.

Polyvinyl alcohol was mixed as an organic binder into the obtained fine powder raw material and granulated.

Next, the granulated powder is molded at a pressure of about sookg/cm to 2 tons/cm, and the granulated powder is molded with a pressure of about 7 mm in diameter x 0 mm in wall thickness. It was made into a disc-shaped molded body of 5 am. This molded body is heated to 1100°C to 1200°C.
Calcinate in air at a temperature in the range of Nt:H
, -95 mol%: 1 in a reducing atmosphere of 5 mol%
It was baked at a temperature of 400°C to 1500'C for 3 hours.

The surface of the obtained sintered body was coated with 0.1% by weight of a glass oxide obtained by vitrifying an oxidizing agent having the composition shown in Table 1 below, and heated at a temperature of 900°C to 1200°C for 2 hours. Heat treated. Finally, indium-gallium alloy is applied to the surface of this unit as an electric bridge, and the varistor voltage (vl, A
), voltage nonlinear coefficient (α), capacitance C, dielectric loss (t
anδ) was set. The results are shown in Table 2.

For comparison, a unit was constructed in the same manner and the characteristics were measured for a unit in which Na oxide (not vitrified) was diffused (samples indicated by symbol M in Tables 1 and 2). shows this comparative example).

As is clear from Table 2, the elements of the examples of the present invention exhibit much larger capacitance than those of the comparative examples, and also have a high voltage nonlinear coefficient α.

Table 1 [Unit: Mol%] Table *: V1*^ is the varistor voltage, C is the capacitance (pF), and α is the voltage nonlinear coefficient.

Next, Figures 1 and 2 show the changes in the amount of glass additives added, the varistor voltage, and the voltage nonlinear coefficient. This shows that.

As is clear from FIG. 1, as the coating amount of the glass additive increases, the varistor voltage VIIIA increases. Therefore, it can be seen that by controlling the coating amount of this glass additive, multifunctional devices with various varistor voltages can be realized.

Moreover, as is clear from FIG. 2, it can be seen that the voltage nonlinear coefficient changes considerably depending on the amount of the glass additive applied. That is, the coating amount of glass oxide is 0.05% by weight.
It can be seen that when the amount is less, the voltage non-linearity coefficient decreases rapidly, and on the other hand, when it exceeds 1% by weight, the voltage non-linearity coefficient decreases rapidly and the varistor characteristics almost disappear. In actual measurements, it was found that when the content exceeds 1% by weight, the varistor properties almost disappear and thermal destruction occurs during measurements.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the varistor voltage and the amount of glass oxide added in an example of the present invention, and Figure 2 is a diagram showing the relationship between the voltage nonlinear coefficient and the amount of glass oxide added in an example of the invention. FIG. Figure 1 Figure 2

Claims (1)

[Claims] The main component is SrTiO_3, contains 0.05 to 1% by weight of at least one selected from the group consisting of rare earth elements, Nb, W, and Ta oxides as a semiconductor agent, and glass oxide is diffused into the grain boundaries. A multifunctional device characterized in that it is constructed using semiconductor porcelain.