JPS5832762B2 - Method for manufacturing barium titanate semiconductor porcelain - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing barium titanate-based semiconductor ceramics having positive resistance-temperature characteristics.

An object of the present invention is to provide a method for manufacturing barium titanate-based semiconductor porcelain that is homogeneous, has a small distribution of resistivity within the element, and has stable characteristics with little variation in resistivity between elements.

Conventionally, La has been added to the basic composition of barium titanate.

It is known that barium titanate-based semiconductor ceramics having positive resistance-temperature characteristics can be obtained by adding one or more of rare earth elements such as Ce and Y, Bi, Sb, Nb, etc.

In addition, by replacing part of Ba with Sr or part of Ti with Sn in this semiconductor ceramic composition, the Curie point (120°C) can be moved to the lower temperature side, or part of Ba can be replaced with P.
It is well known that by substituting with b, the Curie point (120° C.) can be moved to the high temperature side, and it can be used at a high temperature range.

This barium titanate-based semiconductor porcelain is usually produced by wet-mixing the raw material powders that make up the semiconductor porcelain, drying and calcining, then wet-pulverizing the calcined product, and adding an appropriate amount of an organic binder to the dried powder to granulate it. Pressure mold the molded product and stack a plurality of the obtained molded products so that their main surfaces overlap each other, or stabilize Zr0-IF? 1250°: Stabilized ZrO2 particles are sown directly or a molded body is placed on top of it, with a part of the side surface of the molded body touching in the direction of the main surface of the base plate. C-14
It is obtained by firing at 00°C for 0.5 to 3 hours.

Regarding the latter method, such a method is usually adopted in mass production, but in this method, however, the semiconductor porcelain after firing comes into contact with the stabilized ZrO2 plate or the stabilized Zr02 particles. The parts react with them, and as a result, the semiconductor porcelain lacks homogeneity, which leads to variations in resistivity. Furthermore, a distribution of resistivity occurs within one semiconductor porcelain, which causes temperature distribution when it self-heats due to voltage application. This causes significant thermal strain, which can lead to element cracking.

Furthermore, the specific resistance distribution is directly linked to the current density distribution, which causes problems such as a reduction in withstand voltage.

As a way to improve this problem, is it possible to place the molded body on top of a plate with the same or similar composition as the molded body?In this case, especially when the molded body is a disk, it is difficult to fix it, and the work is difficult. It has the disadvantage of being very ineffective.

The manufacturing method of the present invention solves the above-mentioned problems, and involves wet mixing barium titanate-based semiconductor porcelain raw material powder, drying and calcining, and then pulverizing and press-molding to produce a compact. In a manufacturing method in which post-firing is performed, the molded body is erected in the space between the corrugated sintered bodies having a large number of through holes, and a part of the front surface of the molded body is in contact with the space between the bodies in the concave direction. It is characterized by arranging a plurality of sheets side by side so that their main surfaces face each other and then firing them.

According to the manufacturing method of the present invention, there is no need to consider any of the conventional problems.

That is, since the compacts are arranged between the corrugated sintered bodies, it is easy to fix the compacts, and since only part of the side surface of the compact is in contact with the corrugated sintered bodies, a space is created between them, and the corrugated sintered bodies are Since the body is provided with a large number of through-holes, heat can be transmitted through them, allowing for uniform firing, and good air circulation facilitates re-oxidation, thereby stabilizing the properties of the semiconductor porcelain.

Furthermore, since the corrugated sintered body and the molded body used have the same composition, the semiconductor porcelain obtained is homogeneous.

Furthermore, since the contact area between the semiconductor porcelain and the corrugated sintered body after firing is sufficiently small, even when the semiconductor porcelain is to be peeled off from the corrugated sintered body, the workability is good.

Hereinafter, the present invention will be described with reference to examples.

Example First, commercially available industrial raw materials BaCO3, TiO2゜5i0
2, Nb2O5, MnO2 as starting materials and BaCO
31 mol, T i 021 mol 1,5i022° 4 mol %, Nb 2050.11 mol/l/%, Mn 020.
07%/L% composition was mixed in a ball mill to 20%
After time-mixing, the mixture is dried and calcined at 1100°C for 2 hours.

The calcined raw material is wet-pulverized in a 9ic-t←lumil and dried.

After that, add an appropriate amount of organic binder and granulate it to 1000
It is molded into a disc with a diameter of 17 m and a wall thickness of 3.5 m at a pressure of kg/crA.

A plurality of pieces of the molded body obtained in this manner are placed between the corrugated sintered bodies having a large number of through holes made from raw material powder having the same composition as that of the molded body, and each molded body is molded in the concave direction. The proboscis on the side of the body: stand it up so that it touches the concave part,
In addition, the molded bodies are arranged side by side so that their main surfaces face each other.

Figures 1a and 1b show the arrangement at this time.

In FIGS. 1a and 1b, 1 is a molded body and 2 is a corrugated sintered body, which is provided with a large number of through holes.

A part of the side surface of the planar body 1 is placed upright so as to be in contact with the part between the corrugated sintered bodies 2.

Further, due to this arrangement, there is a sufficient space between the molded body 1 and the corrugated sintered body 2 for uniform firing.

Further, 3 is a stabilized ZrO2 plate. After arranging 10 molded bodies in this manner, they were fired in a batch type firing furnace at 1350°C for 1 hour to produce semiconductor porcelain.

The obtained semiconductor porcelain could be easily peeled off from the corrugated sintered body using a razor or the like, and the peeled semiconductor porcelain was uniformly fired.

Ohmic electrodes were provided on both sides of the semiconductor ceramic thus obtained, and the specific resistance at 25°C was measured.

As a result, the specific resistance was 1101-cm (n=average value of IO), which was 140 as a measure of the variation in specific resistance.

Here, X is the average value of the specific resistances of n=10, and xi is each specific resistance.

Further, one of the semiconductor ceramics was taken out and cut into the same area as shown in FIG. 2, and the specific resistance of each piece at 25°C was measured. As a result, A: I 071-cm.

B;105/1. - Steel, C; 1017 - Becomes mercenary,
There was almost no variation in each specific resistance value.

In addition, in FIG. 2, 4 is one of the two contact portions with the corrugated sintered body.

Comparative Example Among the above examples, ZrO2 particles were sown on a ZrO2 plate without using a corrugated sintered body when arranging the molded bodies, and 10 molded bodies were placed thereon in the same manner as in the above example. Semiconductor ceramics were produced in the same manner as in the above examples.

The parts of the obtained semiconductor porcelain that came into contact with the stabilized ZrO2 plate or the stabilized ZrO2 particles and their surroundings reacted and changed color, and lacked the homogeneity of the semiconductor porcelain.

The specific resistance of these semiconductor ceramics was measured by the same method as in the above example 6 As a result, the specific resistance was l 46 ・CIrL(
n=l O average value), and the sum of squares at this time is 618
Met.

Further, one of the semiconductor ceramics was taken out and cut as shown in FIG. 3 in the same manner as in the above example, and the specific resistance was measured.

As a result, D; ILOt-am, E; 10
61-I, F; I 721-It was a hunch, and the specific resistance value varied within the semiconductor porcelain, resulting in a specific resistance distribution.

In addition, in FIG. 3, 5 is a part that comes into contact with the stabilized ZrO2 particles or the stabilized Zr02 plate.

As is clear from the above description, in the case of the method shown in the comparative example, the semiconductor porcelain obtained lacks homogeneity and
A specific resistance distribution occurs within the two semiconductor ceramics.

Furthermore, in order to improve this problem, if a bottom plate having the same composition or similar to that of the molded body is used, it is difficult to fix the molded body and the work efficiency is also poor.

On the other hand, all the semiconductor porcelains obtained by the manufacturing method of the present invention shown in the examples are homogeneous, and the variation in resistivity at 25°C is small, and the resistivity within one semiconductor porcelain is small. It has stable characteristics with little distribution.

Further, the corrugated sintered body used in the manufacturing method of the present invention has the advantage that it can be used for multiple firings.

As described above, the present invention provides a method for manufacturing barium titanate-based semiconductor porcelain that is homogeneous and has stable characteristics with less variation in resistivity and less distribution of resistivity within one semiconductor porcelain. It is something that can be done.

[Brief explanation of drawings]

FIG. 1a is a front view showing the arrangement of a molded body and a corrugated sintered body in the manufacturing method of the present invention, FIG. 1 is a perspective view of the same, and FIGS. FIG. 6 is an explanatory diagram showing cutting locations for measuring the partial resistivity within the semiconductor ceramic in a comparative example. 1... Molded body, 2... Corrugated sintered body.

Claims (1)

[Scope of Claims] 1. A manufacturing method in which barium titanate-based semiconductor porcelain raw material powder is wet mixed, dried and calcined, and then pulverized and pressure-molded to produce a compact, which is then fired. The molded body is placed between the corrugated sintered body having a large number of through holes, and is erected in a concave direction so that a part of the side surface of the molded body is in contact with the space between the bodies, so that the main surfaces of the molded body face each other. A method for producing barium titanate-based semiconductor porcelain, which comprises arranging a plurality of barium titanate semiconductor porcelains in a row and then firing them. 2. The barium titanate-based semiconductor according to claim 1, wherein the molded body and the corrugated sintered body having a large number of through holes are produced from barium titanate-based semiconductor ceramic raw material powder having the same composition. How to make porcelain.