JPS60142502A - Method of baking barium titanate semiconductor porcelain - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application and Purpose of the Invention The present invention is a method for firing barium titanate-based semiconductor porcelain, which is a material for PTC elements, and its purpose is to heat the pad material used during firing. It is an object of the present invention to provide a method for greatly reducing characteristic blurring and blurring caused by firing by improving the method.

BACKGROUND OF THE INVENTION Barium titanate-based semiconductor porcelain is widely used as a heater for constant temperature heating.

Barium titanate-based semiconductor ceramics are generally manufactured by a manufacturing process as shown in FIG.

The firing step during the process greatly influences the characteristics of the porcelain.

In the firing process, a cladding material is sandwiched between the barium titanate-based semiconductor molded body and a firing container, and zirconia powder is used for this padding. This zirconia powder has less reactivity with barium titanate semiconductor ceramics than other pad materials.

However, in recent years, due to the increasing precision required for the characteristics of PTC elements, the reaction between barium titanate semiconductor ceramics and zirconia powder during the firing process cannot be ignored, and there is therefore a demand for the development of new pad materials.

Constituent of the present invention When firing barium titanate-based semiconductor porcelain, zirconia powder is mixed with 20~go, Lfit% of calcined powder of barium titanate-based semiconductor porcelain.
This is a method for firing barium titanate-based semiconductor porcelain, in which the powder is fired at ~1000°C for 1 to 2 hours and then fired as a pad.

Effects: Zirconia powder (100 to 200 meshes) is mixed with 20 calcined powders, which are intermediate pieces of barium titanate semiconductor porcelain.
~80% by weight is blended. This calcined powder is used in the calcining process (1000 to 1250
℃), and in order to uniformly mix it with the zirconia powder, it is ground to the same particle size as the zirconia powder and dry mixed for over 1 hour.

Next, the mixture is fired at 900 to 1000°C for 1 to 2 hours and pulverized to form pad paulownia.

The pad system is placed in a firing container, and a molded body of barium titanate is placed on the pad material or the molded body is embedded in the pad material and fired.

In this case, firing may be performed by a conventionally known method.

The barium titanate-based semiconductor porcelain fired using the pad material as described above has small variations in characteristics as a PTC element, particularly in rush current value, as shown in Examples below, and is therefore stable.

In fact, the calcined powder mixed with the bat powder in the present invention is an intermediate for barium titanate-based semiconductor porcelain, so it is necessary to use a separate raw material, and the firing process is similar to the conventional one. Therefore, stable products with small variations in the characteristics of PTC elements can be obtained simply and at low cost.

Commercially available high-purity products BaCO3+La2 as starting materials
O3, TiO2, Mll(NO3)2, 0,998
, :o, o+s:+, oo:o, o2 (molar ratio), and put into a rubber-lined bot mill together with agate cobbles, crushed, mixed, dried, and calcined at 1100°C for 1 hour. .

A part of the above-mentioned calcined powder was blended with zirconia powder of 100 to 200 mcg in a weight range of O to 90, mixed dry for more than 1 hour, and then heated at 900 to 1000°C for 1 to 90 g.
It was baked for 2 hours and crushed to obtain a pad material.

On the other hand, the calcined powder was again put into the mill together with agate boulders, pulverized and dried. Approximately 5 parts by weight of PVA (polyvinyl alcohol) was added as a binder to the dry raw material, and after granulation, it was pulverized using a hydraulic press. A disc shaped body with an iG diameter of 13 mm and a thickness of 2 mm was obtained at a pressure of .cm/cm2.

This compact was placed on the band plate obtained as described above, heated in an electric furnace at a heating rate of 200°C/1 hour in an alumina container, and fired at 1300°C for 1 hour.
After cooling at a temperature decreasing rate of 0°C/1 hour, nickel electrodes 2 are placed on both sides of the molded body 1 as shown in Fig. 2 to convert the PTC element into a P]'C element with a desired shape of ζ2°. ) Apply a voltage of C12V and observe the change in current value over time. FIG. 3 schematically shows this, and the maximum current value (P) at this time is called the rush current value, and is an important characteristic of the element.

Figure 4 shows the calcined powder of nocurium titanate in the pad material.
It shows the distribution of inrush current values when 0 time factor is mixed. For comparison, FIG. 5 shows a PTC test using conventional pad powder (zirconia powder) in the same manner as in the previous example.
The figure shows the distribution of inrush current values when a voltage of 1) CI 2 V is applied to the element.

As is clear from the comparison of Figures 4 and 5, 1) The variation in the inrush current value of the TC element obtained by the method of the present invention is 6n-1 (standard deviation) smaller than that of the conventional product. It is recognized that

Well, Figure 6 shows the inrush current value as a function of the blending ratio of barium titanate calcined powder during padding.
When the composition of the calcined powder is between 20 and 80% by weight, the variation in rush current value is small, but when the composition is below 20% by weight and above 80% by weight, the variation is large, especially above 80% by weight.
In the second method, the pad material itself was significantly sintered and was not practical.

[Brief explanation of the drawing]

Fig. 1 is a flow sheet of the manufacturing process of the PTC element, Fig. 2 is a cross-sectional view of the PTC element, Fig. 3 is a graph of the change in current value of the PTC element over time, and Fig. 4 is a graph of the product obtained by the present invention. FIG. 5 is a distribution diagram of the inrush current value. FIG. 5 is a similar distribution diagram of a product made by the conventional method. FIG. 6 is a graph of the inrush current value with respect to the mixing ratio of calcined powder. 1. Molding, 2. Electrode. Patent Applicant Toyota Motor Corporation Agent Osamu Ichikawa Yoshido Ton Rlt Tatsuya Figure 1 Price Button ↓ Sunny January

Claims (1)

[Claims] For firing barium titanate-based semiconductor porcelain. Calcined barium titanate powder, which is an intermediate for barium titanate-based semiconductor porcelain, is mixed with zirconia powder in an amount of 20 to 80%, and fired at 900-10'00°C for 1 to 2 hours.The powder is then fired as a pad material. A method for firing barium titanate-based semiconductor porcelain.