JPS6025388B2 - 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 containing Pb.

An object of the present invention is to provide a method for manufacturing barium titanate-based semiconductor porcelain that prevents evaporation of Pb during firing, is homogeneous, has little variation in specific resistance, and has stable characteristics.

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

It is well known that by substituting a portion of Ba with Pb in this semiconductor ceramic composition, it exhibits positive resistance-temperature characteristics in a high temperature range of 120 °C or higher. Semiconductor ceramics having such a composition are widely used as so-called constant temperature heating elements. Recently, it has been put into practical use as a heating element that can be used particularly in a higher temperature range of 250° C. or higher. However, this type of material requires firing at a high temperature of 125,000 °C or higher, and in particular, in materials in which 35 atomic percent or more is substituted with the parent Pb, significant evaporation of Pbo occurs during firing, causing compositional deviation. Electrical characteristics deteriorate,
There was a problem of lack of stability. To improve this, firing in a Pbo or neutral gas atmosphere,
Attempts have been made to sinter the molded body completely covered with powder having the same composition as the molded body to be fired, but in such cases,
It had drawbacks such as poor resistance-temperature characteristics, and lacked practicality. The manufacturing method of the present invention solves the above-mentioned problems, and involves wet mixing barium titanate-based semiconductor porcelain powder containing Pb, drying and calcination, and then wet pulverization. A molded body produced by drying, granulation, and then pressure molding is formed so that a part of the side surface of the molded body is in almost perpendicular contact with the main surface of the adjacent body laid on the flat bottom surface, and In a method for manufacturing barium titanate-based semiconductor porcelain in which a plurality of molded bodies are arranged side by side so that their main surfaces face each other, the group of molded bodies is placed in a concave portion of a first semi-cylindrical sintered body, After arranging the molded bodies side by side so that their main surfaces face each other in the concave direction, a powder having the same composition as that of the molded body is spread around the first semi-cylindrical compact; After surrounding the first semi-cylindrical cryo-feeding body with a second semi-cylindrical cryo-feeding body having relatively large inner and outer diameters, the front and rear spaces of the second semi-cylindrical cryo-feeding body are finally shaped into a flat plate. It is characterized in that it is fired in a sealed compacted body, and furthermore, the molded body, the first and second semi-cylindrical fired striped bodies, and the flat plate-shaped sintered body have the same composition. Moreover, a large number of through holes are provided near the ends of both sides of the second semi-cylindrical sintered body.

Next, the present invention will be explained by giving examples.

First, commercially available industrial raw materials BaC03, Tj02, PO0,
Using Si02, NQQ, Mn(N03)2 as starting materials,
B8C.

30.6 mol Ti.

21 mol, Pb.

0.4 mol, Si.

22.4 mol%, Nb2QO. 11 mol%, Mn (N.

3) A mixture of 2 and Mn with a composition of 0.03 atomic % was wet-mixed in a ball mill and dried.
Calcinate at 0°C for 2 hours. Next, the temporary powder was wet-milled in a ball mill for 2 hours and dried. Add an appropriate amount of organic/vinyl to this, granulate it, mold it at a pressure of 1000k9/ground,
A disk with a diameter of 20 ribs and a thickness of 3.5 ribs is prepared. The disks 1 are arranged in a concave portion of the first semi-cylindrical body in a substantially vertical line so that the principal surfaces of the disks face each other in the direction of the concave surface. Further, powder having the same composition as the compact is spread around the first semi-cylindrical compact. Next, a second semi-cylindrical bran compact is placed over the first semi-cylindrical sintered compact, and finally, the space before and after the second semi-cylindrical bran compact is sealed with a flat plate-shaped bran compact. .

The first and second semi-cylindrical sintered stripes and the flat sintered body used here had the same composition as the molded body. Further, a large number of through holes are provided near both side portions of the side surface of the second semi-cylindrical composite body. An example of the arrangement state at this time is shown in the drawing. In the figure, 1 is a molded body, 2 is a first semi-cylindrical sintered body, and 3 is a second semi-cylindrical sintered body, and a large number of through holes 3' are provided near both end portions of this side surface. It is being

4 is a powder having the same composition as compact 1, 5 is 2 particles of Z,
6 is a pod.

With this configuration, the binder can be completely removed during firing due to the noble holes provided.
In addition, the evaporation of Pb is extremely low since the through hole is sealed, and since it is made of the same composition as the molded object, a uniform atmosphere is created around the molded object. Air and heat can also be supplied, allowing for uniform firing. With this arrangement method, 125
Semiconductor porcelain was produced by firing at 0q0 for 1 hour.

All of the semiconductor porcelain thus obtained were fired homogeneously without any color unevenness.

Ohmic electrodes were provided on both sides of this IN solid semiconductor ceramic, and the specific resistance at 25 qC was measured. the result,
It was 6.5 x 1 x 1 (average value of 10). In addition, as a guide for the variation in resistivity, the sum of squares is S=imine, (Xi
-X)2 (n=10) formula, it was 8.5×1, and had stable characteristics with little variation in resistivity. Comparative Example A semiconductor porcelain was produced in the same manner as in the example except that the molded bodies of the above example were simply arranged side by side on the flat bottom surface of the pod with their main surfaces facing each other, and a normal pod was covered with a lid. .

Some of the obtained semiconductor porcelains were discolored, some had pores on the surface, and lacked homogeneity. Further, the specific resistance of this semiconductor ceramic was measured in the same manner as in the example.
As a result, the specific resistance was as high as 1.5 x 1 pQ skin, and the sum of squares was 9.8 x 1'', which showed large variations and was not suitable for practical use. As is clear from the above results, the conventional method causes significant evaporation of Pbo, leading to non-uniformity of the semiconductor porcelain, and large variations in resistivity, making it impractical, whereas the semiconductor porcelain manufactured by the method of the present invention It is highly homogeneous, has small variations in specific resistance, and has stable characteristics.

[Brief explanation of the drawing]

The drawing is a sectional front view showing the arrangement of molded bodies when carrying out the manufacturing method of the present invention. 1... Molded body, 2... First semi-cylindrical burning body, 3... Second semi-cylindrical burning silk body,
3'...Through hole, 4...Powder, 5...
...Zr02 particles, 6...Goya.

Claims (1)

[Claims] 1 Pb-containing barium titanate semiconductor porcelain raw material powder is wet mixed, dried and calcined, then wet powdered, dried, granulated, and then pressure molded to produce a molded body. A plurality of titanium bodies are arranged and fired so that a part of the side surface of the molded body is in almost perpendicular contact with the main surface of the sintered body laid on the flat bottom surface of the sheath, and the main surfaces of the molded bodies are facing each other. In the method for manufacturing barium acid semiconductor ceramics, the group of molded bodies is placed in a concave portion of a first semi-cylindrical sintered body having the same composition as the molded body, and the main surfaces of the molded bodies face each other in the concave direction. After arranging the first semi-cylindrical sintered body, powder having the same composition as that of the compact is spread around the first semi-cylindrical sintered body, and then the first semi-cylindrical sintered body is placed so that the inner diameter and outer diameter thereof are relative to each other. After enclosing the molded body with a second semi-cylindrical sintered body having the same composition as the molded body and having a large number of through holes near the ends of both sides, finally, the front and rear of the second semi-cylindrical sintered body are A method for manufacturing barium titanate-based semiconductor porcelain, characterized in that the space is sealed with a flat sintered body having the same composition as the molded body and fired.