JP3252649B2 - Method for firing ceramic molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for firing a ceramic compact.

[0002]

2. Description of the Related Art Positive temperature coefficient thermistor elements, which are barium titanate-based semiconductor porcelains, have an overcurrent control function and a self-temperature control function because they are semiconductor ceramics whose resistance value rapidly increases at a certain temperature. It is well known and widely used as a temperature sensor, an overcurrent control element, and a convenient heating element with little change in surface temperature.

[0003] A method of firing a barium titanate-based semiconductor porcelain, which is a kind of conventional ceramic porcelain, will be described below.

FIG. 3 is a diagram in which a conventional barium titanate-based compact is housed in a firing sheath when firing a conventional barium titanate-based semiconductor porcelain. In FIG. 3, reference numeral 1 denotes a firing sheath, 2 denotes a barium titanate-based compact, and 3 denotes a zirconia powder. Generally, an alumina-based firing sheath 1 is laid with zirconia powder 3, and a barium titanate-based powder is placed thereon. Were fired at a high temperature of 1200 ° C. to 1400 ° C. in a single furnace or a tunnel furnace capable of setting the temperature.

[0005]

However, in the conventional structure described above, the barium titanate-based compacts 2 housed in the firing sheath 1 react during firing because the compacts 2 are in contact with each other. Since the sintered body of the barium titanate-based semiconductor porcelain obtained by firing at a high temperature has an extremely large amount of dust, it takes a lot of time to remove the dust. In addition, during the operation of peeling off the cracks, the appearance of the sintered body is broken due to cracking, and there is a problem that the working efficiency is extremely poor in manufacturing.

Accordingly, the present invention is to solve the above-mentioned conventional problems, and it is possible to improve the work efficiency in manufacturing by suppressing the reaction between ceramic molded bodies and obtaining a sintered body with less dustiness. It is an object of the present invention to provide a method for firing a ceramic molded body.

[0007]

In order to achieve this object, a method for firing a ceramic molded body according to the present invention is characterized in that, at the time of firing, a portion of the outer peripheral surface of the ceramic molded body in contact with another ceramic molded body is contacted with zirconia powder at room temperature. And spraying and adhering and fixing a powder mixed with a solid organic solvent, and then firing the ceramic molded body.

[0008]

According to this structure, the contact between the ceramic molded bodies is reduced, the reaction between the ceramic molded bodies is suppressed, the work for peeling off the dust after firing is reduced, the work efficiency is improved, and the appearance defect can be prevented.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, taking a barium titanate-based compact as a kind of ceramic compact as an example. 1 and 2 show a method for firing a barium titanate-based molded body according to an embodiment of the present invention. FIG. 1 is a sectional view of a barium titanate-based molded body before being housed in a firing sheath. FIG. 2 shows a state in which a plurality of barium titanate-based compacts are housed in a firing sheath. In FIG. 1, 4 is a barium titanate-based compact, 5 is a powder obtained by mixing polyethylene glycol and zirconia powder, 6 is zirconia powder,
Reference numeral 7 denotes a baking sheath, for example, an alumina baking sheath. Here, a powder 5 obtained by mixing polyethylene glycol and zirconia powder is adhered and fixed to the upper surface of the barium titanate-based compact 4.

A specific example of the method of firing the barium titanate-based compact 4 having the above-described structure will be described with reference to FIGS. First, 1% by weight of powdered polyethylene glycol was added to zirconia powder.
Is heated and dissolved in water, and then mixed with zirconia powder and cooled to prepare a powder 5 in which polyethylene glycol and zirconia are mixed.
Then, the powder 5 is sprayed on the surface of the barium titanate-based compact 4 and heated in a drier at a temperature of 100 ° C. for 10 minutes, taken out of the drier, and left at room temperature.
Polyethylene glycol having a molecular weight of 1000 or more is a solid at room temperature, but becomes liquid by applying heat at a temperature of 80 ° C. or higher. Is fixed to the molded body 4. Then, as shown in FIG. 2, 500 pieces of barium titanate-based compacts 4 to which powder 5 was adhered and fixed were housed in an alumina-based firing sheath 7 with a zirconia powder 6 spread on the bottom surface. The firing was performed.

Further, the firing method of the barium titanate-based compact 4 according to the present embodiment and the conventional method of firing the barium titanate-based compact are shown in Table 1 below.

[0012]

[Table 1] From this (Table 1), it can be seen that when coarse particles having a particle size of less than 100 mesh are used for the zirconia powder mixed with polyethylene glycol, the adhesion and fixing force of the powder 5 obtained by mixing polyethylene glycol and zirconia to the barium titanate-based molded product Is reduced, and the barium titanate-based sintered body obtained after the firing is more frequently cut. Further, the obtained sintered body of the barium titanate-based semiconductor porcelain is provided with irregularities, so that it is impossible to prevent the appearance defect. In addition, polyethylene glycol having a molecular weight of less than 1000 is a liquid at room temperature and is therefore powdery.
Not only is difficult to spray on the molded body 4 but also is not fixed to the barium titanate-based molded body 4, resulting in increased stickiness, poor work efficiency and inability to prevent poor appearance.

As is clear from Table 1, the method of firing the barium titanate-based molded body 4 according to the present embodiment is as follows.
An excellent effect is obtained in that appearance defects can be prevented and work efficiency in manufacturing can be improved.

In this embodiment, polyethylene glycol having a molecular weight of 1000 or more is used as an organic solvent which is solid at ordinary temperature. However, when the solid is used at the working temperature and the workability is taken into consideration, the melting point is about 50 ° C. or more. Any organic solvent may be used as long as the temperature is not so high (around 100 ° C.).

The mixing ratio of the polyethylene glycol and the zirconia powder may be any as long as the zirconia powder is present on the molded body 4 when sprayed on the surface of the molded body 4.

Further, the powder 5 may be sprayed on the surface of the compact 4 so that it exists between the compacts 4 when the compact 4 is stored in the sheath 7 for firing. Absent. In addition, it is not necessary to apply the zirconia powder evenly on the surface of the molded body 4 as far as the zirconia powder is present.

The shape of the compact 4 and the arrangement of the compact 4 in the firing sheath 7 are not limited to the present embodiment.

As described above, according to the present embodiment, the powder 5 obtained by mixing polyethylene glycol and zirconia powder is sprayed on the surface of the barium titanate-based compact 4 and adhered and fixed to form the barium titanate-based compact. By firing the body 4, appearance defects can be prevented, and work efficiency can be improved in manufacturing.

[0019]

As described above, the present invention provides a method in which a powder obtained by mixing a solid organic solvent and zirconia powder at room temperature is sprayed on the surface of a ceramic molded body, adhered and fixed, and then fired by firing the molded body. In addition, by suppressing the reaction between the compacts and obtaining a sintered compact with less cracking, it is possible to improve work efficiency in manufacturing. Further, by firing in this way, appearance defects can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a barium titanate-based compact according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a firing sheath accommodating a barium titanate-based compact according to one embodiment of the present invention.

FIG. 3 is a cross-sectional view of a firing sheath containing a conventional barium titanate-based compact.

[Explanation of symbols]

 4 compact 5 powder

Claims (4)

(57) [Claims] At the time of firing, a powder obtained by mixing zirconia powder and a solid organic solvent at room temperature is dispersed and adhered to a portion of the outer peripheral surface of the ceramic molded body which is in contact with another ceramic molded body. And a method for firing the ceramic molded body. 2. The method according to claim 1, wherein polyethylene glycol is used as an organic solvent which is solid at room temperature. 3. The method according to claim 2, wherein polyethylene glycol having a molecular weight of 1,000 or more is used. 4. The method according to claim 1, wherein zirconia powder having a particle size of 100 mesh or more is used.