JPS6112877B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a ceramic firing sheath and a firing method thereof, which make it possible to fire a ceramic composition containing components that tend to be thermally volatile during firing so that the composition does not change due to firing. Conventionally, when firing ceramic compositions containing thermally volatile components such as Pb and Bi, A ₂ O ₃ ,
There is a method in which the object to be fired (ceramic composition) and a powder or molded object of the same material or thermally volatile components are placed side by side as a dummy in a pod made of MgO or Al ₂ O ₃ -MgO compound and then fired. It is being done. In other words, during firing, thermally volatile components from the dummy fill the pod, and the effect of the vapor pressure suppresses the volatilization of thermally volatile components from the object to be fired, resulting in a change in composition due to firing. This method is widely used because it eliminates fluctuations. Here, as an example of the effect of dummy juxtaposition during firing, ZnO−Bi ₂ O ₃ −C ₀ O−MnO−Sb ₂ O ₃
Table 1 shows the results of the firing experiment for the ZnO varistor. This experiment was conducted by gradually increasing the dummy amount from zero, and the results were as follows: 1. Bi in the fired body
2. Electrical properties (0.1mA ≓ 1mA...index of voltage-current nonlinearity)
This shows that.

【table】

[Table] In this experiment, the object to be fired was made by granulating the raw materials with the above composition with an organic binder (PVA).
A disk shaped into a φ5×1 ^t disk was used. Firing temperature = 1250°C, pod volume = ^100cm3 . From the above results, ZnO−Bi ₂ O ₃ −C ₀ O−MnO−
When firing Sb ₂ O ₃ -based ZnO varistors, it has become clear that when the dummy amount is zero or extremely small, the Bi component volatilizes a lot, and as a result, it has a large effect on the electrical characteristics, and it is necessary to suppress such phenomena. In order to do this, it was found that it was necessary to place a dummy of the same composition as the object to be fired in the pod and fire it. When firing a ceramic composition containing a thermally volatile component in this way, the pod has the same composition as the object to be fired, or the volatile component is used as a dummy, as shown in Figure 1.
Juxtaposition has been done for a long time, and
The basis for this is also clear from the above experiment. here,
1 is a pod, 2 is an object to be fired, 3 is a dummy, and 4 is a pod lid. However, in actual mass production, there are problems such as the hassle of filling the dummy into the pod and the amount of the object to be fired being packed into the pod due to filling the dummy into the pod in a limited space. Improvement is required. The present invention relates to a firing pod and a firing method aimed at solving the problems of the conventional method (dummy juxtaposition). The material of the sheath 5 used in the present invention is Al ₂ O ₃ −MgO
Alternatively, it is a refractory made of Al ₂ O ₃ --MgO compound, and has many openings 6 with a diameter of 1 mm or less, as shown in FIG. When firing a ceramic composition containing easily volatile components using this pod, the same composition as the object to be fired or the easily volatile components is made into a slurry by adding pure water, and the porous pod is placed in the slurry. After impregnation, open the pores of the porous pod using reduced pressure or other methods.
Penetrate the slurry into the The pods are then removed from the slurry and allowed to dry in the air. In this way, the object to be fired 7 is placed in the pod 5 whose holes contain the desired components, as shown in FIG. 2, and fired. Here, 8 is a pod lid. Of course, this shell lid 8 is also provided with an opening 6. The case of firing a ZnO-Bi ₂ O ₃ -C ₀ O-MnO-Sb ₂ O _3- based ZnO varistor will be described. An Al ₂ O _3- based pod with many pores with a diameter of 1 mm or less is impregnated into a slurry having the same composition as the ZnO varistor (raw material: pure water = 100:150), and the slurry is poured into the pores by reducing the pressure. Impregnate. Thereafter, the pods are taken out and dried in air at 80° C. for 20 hours. The molded body to be fired is normally packed into the pod treated in this way and fired at 1250°C. The results are shown in Table 2. For comparison, the results of fired body samples obtained by the conventional method (dummy juxtaposition, 30 g/100 cm ³ ) are also listed.

[Table] From the above, by using the sheath and firing method of the present invention, the fired sample can similarly prevent the volatilization of the Bi component compared to the conventional dummy juxtaposition method, and also has electrical properties. It is also possible to obtain a fired ceramic body that is not inferior in terms of both aspects. In addition, since no dummy is placed in the pod as in the conventional method, there is no restriction on the amount of objects to be fired in the pod, and the process is easy. Note that once used pods can be easily regenerated by soaking them in aqua regia or the like to elute the components that have entered the pores.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view for explaining a conventional ceramic firing method, and FIG. 2 is a cross-sectional view for explaining a ceramic firing sheath and firing method in an embodiment of the present invention. 5... pod for firing, 6... opening, 7... object to be fired, 8... pod lid.

Claims (1)

[Claims] 1. It has many openings with a diameter of 1 mm or less, and the material is A.
Ceramic firing characterized in that it is made of a refractory material such as ₂ O ₃ , MgO, or a compound thereof, and the openings are impregnated with a material having the same composition as the object to be fired, or a volatile component in the above composition. Saya for use. 2 A with many openings with a diameter of 1 mm or less
A ceramic composition containing a thermally volatile component or a volatile component in the above composition is impregnated into the openings of the pod made of ₂ O ₃ , MgO, or a compound thereof, and in this state, the pod is filled with the pod. 1. A method for firing ceramics, comprising: inserting an object to be fired and firing; and repeating impregnating the pod with the composition of the object to be fired or a volatile component in the composition every several firings.