JPH03177363A - Method for burning semiconductor ceramics - Google Patents

Abstract

PURPOSE:To reduce dispersion in resistance value in a burning sheath in burning a large amount thereof by covering a perforated auxiliary sheath on an opening formed in a sheath bottom in burning a ceramic compact sensitive to a reducing atmosphere on placing powder on a setter in the burning sheath. CONSTITUTION:An opening 17 having an area corresponding to about 1% based on the bottom area is provided in the bottom of a burning sheath 11 and covered with an auxiliary sheath 19 perforated in a honeycomb form. Corrugated setters 12 are then placed on the bottom of the sheath 11 and placing powder 13 is laid thereon to arrange ring compacts 14 composed of a semiconductor ceramic material thereon. Further, zirconia side plates 18 are arranged on the inner wall surfaces of the sheath 11 for filling thereof so as to prevent the compacts 14 from directly touching the inner walls of the sheath 11. A lid 16 is placed through a spacer 15 on the top opening of the sheath 11 to carry out burning in the air in a tunnel kiln. Air flows through the opening 17 to reduce the dispersion in resistance value in the sheath 11 according to the aforementioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for firing semiconductor ceramics that are sensitive to a reducing atmosphere during firing, such as barium titanate semiconductor ceramics.

Conventional technology Barium titanate (BaTiO:+)-based semiconductor porcelain, which is a ceramic that is sensitive to the reducing atmosphere during firing, exhibits a positive temperature coefficient of resistance that shows a rapid increase in resistance near the Curie point. Utilizing these characteristics, it is widely applied to constant temperature heating element 9, current control element, temperature control element, etc.

Then, the aTiO:+ semiconductor porcelain becomes B
aCO3, T i 02. Main raw materials such as PbO, SrcO3゜, additives such as Aj' 203+ SiO2, and semiconducting materials such as Y2O3, Nb2O5, rare earths, etc. are weighed and blended, wet-mixed, and then 1050~12
It is calcined in the air at a temperature of 00°C for about 2 hours, then crushed in a ball mill, added with a binder and granulated, then compression molded into a predetermined shape, and then the molded body is molded in an electric furnace. It is obtained by baking it in the air at a temperature of 1300 to 1350°C for about 2 hours.

Conventionally, the firing method for BaTiC)+ based semiconductor porcelain is based on the fourth method.
The configuration was as shown in the figure. In Figure 4,
1 is a firing sheath, 2 is a corrugated setter 3 is a bedding powder made of ZrO2, 4 is a ring-shaped molded body made of BaTi0:+ semiconductor porcelain, 5 is a spacer, 6 is a lid, and 7 is a zirconia side plate.

And BaTi0. The firing process of + series semiconductor porcelain is important because its resistance value characteristics are affected by firing. Additionally, tunnel furnaces are commonly used for mass firing.
The pods are packed horizontally and fired in bulk.

Problems to be Solved by the Invention In the conventional configuration as described above, when the molded body takes a ring shape, the molded body may be partially reduced by the reducing gas generated by the decomposition of the binder of the molded body. Due to non-uniform heat distribution between the inside of the pod and the wall side, reoxidation of the molded body does not occur uniformly. There was a problem in that the variation in resistance value within the range increased.

In view of these problems, it is an object of the present invention to provide a method for firing semiconductor ceramics that can reduce resistance value variations within a pod during mass firing.

Means for Solving the Problems In order to solve this problem, the present invention provides a firing pod which has holes in its bottom and covers the holes with an auxiliary pod having honeycomb-like holes on the sides. A molded body made of a semiconductor ceramic material that is sensitive to the reducing atmosphere during firing is placed on top of the powder spread on the center, and a lid is placed on the upper opening of the firing pod to remove the molded body. It is designed to be fired.

Function The present invention has the above-mentioned configuration, with an opening provided at the bottom of the pod,
By covering the auxiliary pod with honeycomb-like holes on the side over the hole between the holes, an air flow path is established, and reducing gas generated by binder decomposition can be smoothly removed, and inside the pod. The uniformity of the heat distribution and the uniformity of reoxidation are improved, and it is possible to reduce the variation in resistance value within the pod.

Embodiment FIG. 1 is a sectional view for explaining a method of firing barium titanate-based semiconductor porcelain according to an embodiment of the present invention. In Fig. 1, 1■ is a sheath for firing, 12 is a waveform setter, 13 is a bedding powder made of ZrO2, 14 is a ring-shaped molded body made of BaTiO3 semiconductor porcelain, 15 is a spacer, 16 is a lid, and 17 is for baking. An opening provided at the bottom of the sheath 11, 18 is a zirconia side plate, and 19 is an auxiliary sheath with honeycomb-shaped holes on the side as shown in FIG.
It is placed over the opening 17. Then, as shown in Figure 1, for example, 270 mm long x 270 mm wide x
An opening 17 corresponding to 1% of the bottom area is provided at the bottom of the firing pod 11 with a height of 90 mm, and an auxiliary pod 19 ( The hole area is covered by 1% to 5% of the side surface area. Further, a wave setter 12 made of alumina is placed on the bottom of the firing sheath 11, a bedding powder 13 made of ZrO2 is placed thereon, and ring-shaped molded bodies 14 are arranged on the bedding powder 13. moreover,
A zirconia side plate 18 is placed on the inner wall surface of the firing sheath 11,
The ring-shaped molded body 14 is packed in the pod so that it does not directly contact the inner wall of the firing pod 11. Further, the lid 16 was placed on the upper opening of the firing pod 11 via the spacer 15, and fired in the atmosphere in a tunnel furnace at a temperature of 1300°C to 1350°C.

Here, if the size of the opening 17 is too wide, the firing pod 11
strength is reduced, and the number of ring-shaped molded bodies 14 packed into the pod 11 is reduced, resulting in a drop in productivity. On the other hand, if it is too narrow, air circulation will be poor and the effect of reducing resistance value variations within the sheath 11 will be lost. In addition, the side hole area of the auxiliary pod 19 with honeycomb-shaped holes on the side is 1 to 5% of the side surface area.
Good. That is, if it is less than 1%, there is no effect of reducing resistance value variation. On the other hand, if the width exceeds 5%, the strength decreases, so a range of about 1 to 5% is preferable. Next, when comparing the resistance value variation within the pod of the BaTi0:+ semiconductor porcelain fired as described above between the conventional old pottery and the method of the present invention, as shown in FIG. It can be seen that the variation in resistance within the pod is extremely small. Here, the variation display is (sigma/average value)
xloo (%) was used.

Note that the present invention is not limited to the BaTi0:+ semiconductor ceramics of the above embodiments, but can also be applied to other semiconductor ceramics that are sensitive to the reducing atmosphere during firing.

Effects of the Invention As described above, according to the present invention, it is possible to reduce the variation in the resistance value within the pod of semiconductor ceramics, such as barium titanate-based semiconductor ceramics, which are sensitive to the reducing atmosphere during firing, and to ensure stable firing. It is possible, and the effect of contributing to productivity improvement can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view for explaining a method of firing barium titanate-based semiconductor porcelain according to an embodiment of the present invention, FIG. 2 is a perspective view of an auxiliary sheath used in the method of the present invention, and FIG. 3 is a diagram of the present invention. FIG. 4 is a cross-sectional view for explaining the firing method of the conventional method. 11... Saya for firing, 12... Corrugated setter 13... Powder, 14... Ring shaped molded body, 15... Spacer , 16...
... Lid, 17... Openings, 18... Zirconia side plate, 19... Lid with honeycomb-shaped holes on the side.

Claims (1)

[Claims] A setter is placed inside a firing pod with a hole in the bottom and an auxiliary pod with honeycomb-shaped holes on the side is placed over the opening, and the setter is placed on top of the bedding powder during firing. A method for firing semiconductor ceramics, comprising arranging molded bodies made of a semiconductor ceramic material sensitive to a reducing atmosphere, and firing the molded bodies by placing a lid on the upper opening of the firing pod.