JPS6045149B2 - 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 suppresses evaporation of H° during the firing process and has homogeneous and stable characteristics.

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

Furthermore, it is well known that by substituting a part of No. of this semiconductor ceramic composition with Pb, barium titanate-based semiconductor ceramics having positive resistance temperature characteristics in the high temperature range of 120° C. or higher can be obtained. . Semiconductor ceramics having a composition containing Pb are widely used as so-called constant-temperature heating elements, and recently, efforts have been made to put into practical use heating elements that can be used in high-temperature regions of 250° C. or higher. However, the biggest drawback of this type of composition system is that, especially in materials in which a part of Ba is replaced with Pb at 35 atomic percent or more, when fired at a high temperature of 1250°C or higher, the evaporation of Ho becomes significant, resulting in a composition of As a result, the resulting semiconductor porcelain lacked homogeneity and stability of properties. In even worse cases, many holes were formed on the surface of the porcelain. Conventionally, in order to eliminate these drawbacks, attempts have been made to sinter the molded product in a PbO or neutral gas atmosphere, or to sinter the molded product in a state where the molded product is completely covered with powder having the same composition as the molded product to be fired. However, in both cases a problem arose in that the resistance-temperature characteristics of the resulting semiconductor ceramics deteriorated.

The manufacturing method of the present invention eliminates such conventional drawbacks, and involves wet mixing barium titanate semiconductor ceramic raw material powder containing Pb, drying and calcining, and then
In a method for manufacturing barium titanate semiconductor porcelain, in which a molded body produced by pulverization and pressure molding is stacked with the main surfaces of the molded bodies together and fired, a powder having the same composition as the molded body is placed around the molded body. After that, the molded body is surrounded by five cylindrical sintered bodies having the same composition as the molded body and having a large number of through holes on the side surface, and then a lid is covered with a disc-shaped sintered body having the same composition as the molded body. It is characterized by being heated and fired. According to the present invention, a powder having the same composition as the molded body is spread around the molded body, and a cylindrical sintered body surrounding the molded body and a disc-shaped sintered body used as a lid. Since both have the same composition as the molded body, a uniform lead atmosphere is maintained.

Furthermore, since the side surface of the cylindrical sintered body is provided with a large number of through holes, the binder can be completely removed during the firing process, and air and heat are simultaneously supplied through the through holes. Barium acid semiconductor ceramics are homogeneous and maintain their characteristics as semiconductor ceramics without losing their characteristics, and furthermore, stable characteristics can be obtained by uniform firing. The present invention will be described below with reference to Examples.
First, commercially available industrial raw materials BaCO3, TiO2, PbO
, SjO2, NY)205, Mn(NO3)2 as a starting material, BaCO3O. 6 mol, TiO2l mol, P
bOO. 4 mol, SlO22.4 mol%, Nb2O. O
．． 11 mol % and Mn in a composition of 0.03 atomic % were wet mixed in a ball mill for a period of time, dried, and calcined at 1000° C. for 2 hours.

The calcined raw material is further wet-pulverized in a ball mill and dried. After that, add an appropriate amount of organic binder and granulate it to 10
00k9/CTl pressure, diameter 20TfrIn, thickness 3
．． Form into a 5w1 disc. The seven molded bodies thus obtained were stacked so that their main surfaces overlapped each other. At this time, granulated powder having the same composition as the molded body is sprinkled on the overlapping main surfaces so that each semiconductor porcelain can be easily peeled off after firing. Powder having the same composition as the compacts is spread around the stacked compacts. A large number of through holes are provided on the rear side surface.Inner diameter: 57wt1Outer diameter: 60TnJn1Wall thickness: 1.
5? , height 50? A cylindrical sintered body surrounds the molded body,
Finally, cover the disc-shaped sintered body with a lid. The cylindrical sintered body and disc-shaped sintered body used here all have the same composition as the molded body.

The arrangement state at this time is shown in FIG. In the figure, 1 is a molded body, 2 is a cylindrical sintered body with a large number of through holes 3, 4 is a powder made of 4 having the same composition as the molded body, 5 is a disk-shaped sintered body, and 6
is a ZrO2 particle, and 7 is a ZrO2 plate. The thus arranged molded bodies were fired in a batch type firing furnace at 1250°C for 1 hour to produce semiconductor porcelain. The obtained semiconductor porcelain was homogeneously sintered without color unevenness. This semiconductor
The bottom row of porcelains was excluded, and ohmic electrodes were applied to both sides of the semiconductor porcelains for the remaining 6 pieces.
The specific resistance at 5°C was measured. As a result, the specific resistance is 6.
5×1σΩ. Cm (average value of 6 pieces), and as a measure of the variation in specific resistance, the sum of squares is S=, Ei, (Xi-X)2
(where n=6) The result was 4.5×103. Comparative Example 1 Semiconductor porcelain was produced in the same manner as in the above Examples except that seven molded bodies were simply stacked.

A large number of holes are formed in some of the obtained semiconductor porcelains,
The side surfaces were discolored and were non-uniform. This semiconductor ceramic was measured in the same manner as in the example. As a result, the specific resistance was 1.8×103Ω. C77! (average value of 6), and the sum of squares at this time was 7.3×1CP. Comparative Example 2 Seven molded bodies from the above example were stacked, and then a powder having the same composition as the molded bodies was simply placed on top of the molded bodies so that all of the molded bodies were covered. Semiconductor porcelain was produced using

The obtained semiconductor porcelain was measured in the same manner as in the example. As a result, the specific resistance was 5.8×1σΩ. Cm, and the sum of squares at this time was 5.2×10 3 . Furthermore, the resistance-temperature characteristics of the semiconductor ceramics obtained in Examples and Comparative Examples 1 and 2 were investigated using a small electric furnace.

The results are shown in FIG. In FIG. 2, A shows the characteristics of the semiconductor porcelain obtained in the example of the present invention, and B and C show the characteristics of the semiconductor porcelain produced in Comparative Examples 1 and 2, respectively. be.

As is clear from the above results, the semiconductor ceramic of Comparative Example 1 is non-uniform and has an abnormally high specific resistance, and the variation in specific resistance is also extremely large, making it impractical.

In addition, the semiconductor porcelain of Comparative Example 2 has high homogeneity with little variation in resistivity, but the resistance temperature characteristics deteriorate,
Bad condition. In contrast, the semiconductor porcelain obtained by the manufacturing method of the present invention is homogeneous, has a low specific resistance, has very little variation, is highly stable, and has good resistance-temperature characteristics, making it a practical semiconductor porcelain. It can be said. As described above, according to the manufacturing method of the present invention, barium titanate-based semiconductor porcelain containing Pb, which has homogeneous and stable characteristics and has extremely high practical value, can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional front view showing the arrangement of molded bodies when carrying out the manufacturing method of the present invention, and FIG. 2 is a resistance characteristic diagram of semiconductor ceramics obtained in an example of the present invention and in comparison. 1... Molded body, 2... Cylindrical sintered body,
3...shell hole, 4...powder, 5...
...Disc-shaped sintered body.

Claims (1)

[Claims] 1 Pb-containing barium titanate-based semiconductor porcelain raw material powder is wet mixed, dried and calcined, then pulverized and pressure molded to produce a molded body, which is then stacked with its main surfaces on top of each other. In the method for manufacturing barium titanate-based semiconductor porcelain, which is fired by heating, a powder having the same composition as the compact is spread around the compact, and the compact has a large number of through holes in the side surface. A method for producing barium titanate-based semiconductor porcelain, which comprises surrounding the cylindrical sintered body with a cylindrical sintered body, then capping the body with a disk-shaped sintered body having the same composition as the molded body, and firing the cylindrical sintered body.