JPS6328323B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a positive characteristic ceramic semiconductor, particularly a BaTiO ₃ -based semiconductor, and uses of this ceramic semiconductor include resistors, current control devices, heating elements, and the like. The conventionally well-known method for producing BaTiO ₃ -based positive characteristic ceramic semiconductors involves adding rare earth elements or similar elements to BaTiO ₃ as a semiconductor additive, and further adding SiO ₂ , TiO ₂ , Al ₂ O ₃ , etc. as a semiconductor catalyst. It has a positive temperature coefficient of resistance by adding a small amount of one or more of the oxides and sintering it.
A BaTiO ₃ based ceramic semiconductor is obtained. In conventional methods for producing BaTiO ₃ -based ceramic semiconductors, oxides such as SiO ₂ , Al ₂ O ₃ and TiO ₂ are added as semiconductor accelerators. However, when firing BaTiO ₃ -based ceramic semiconductors, this accelerator oxide and
Some of the Ba and Ti elements that make up BaTiO ₃ react to form other compounds (for example, Ba ₂ TiSi ₂ O ₈ ).
Therefore, the ratio of Ba and Ti in BaTiO ₃ changes,
It has the disadvantage of increasing the specific resistance of the ceramic semiconductor. In addition, the amount of compounds such as Ba ₂ TiSi ₂ O ₈ produced is
Since it depends on the manufacturing conditions, there is a drawback that the resistivity of the porcelain varies depending on the amount of the compound. In view of the above points, the present invention incorporates a barium-titatinium-silicate-based compound such as the above-mentioned Ba ₂ TiSi ₂ O ₈ or barium such as BaSiO ₃ into a material for making a BaTiO ₃ -based positive characteristic ceramic semiconductor as a semiconductor accelerator.・The purpose is to provide a manufacturing method that can reduce the variation in resistivity of the obtained positive characteristic ceramic semiconductor by adding 0.5 to 8.0% by weight of a silicate compound and firing it, and can also lower the resistivity itself. It is something. The present invention will be explained in detail below using specific examples. Example 1 2 moles of BaCO ₃ , 1 mole of TiO ₂ , and 2 moles of SiO ₂ are mixed together, distilled water is added thereto, and wet mixing is carried out for 20 hours. After drying, it is fired at 800℃~1200℃,
Obtain Ba ₂ TiSi ₂ O ₈ . Next, 1 mol of BaCO ₃ , 1 mol of TiO ₂ , and 0.2 mol % of Y ₂ O ₃ were mixed, and to this was added 1.27 mol % of
Mix _PbTiO3 . 0.3 to 1% by weight of polyvinyl alcohol is added to this mixture, and about 1.6 times as much distilled water is added to the mixture, and an appropriate amount of the above Ba ₂ TiSi ₂ O ₈ is added. These are wet-pulverized, and the resulting slurry is dried and granulated using a spray dryer and press-molded. This molded product is heated to 1200℃.
A positive characteristic ceramic semiconductor is obtained by firing at ~1400°C for 1 to 2 hours. The semiconductor has a disk shape with a diameter of 25 mm and a thickness of 3 mm. Ohmic Ni electrodes are formed on both sides of this semiconductor by electroless plating, and then Ag paste is applied onto the Ni electrodes and the Ag is baked at 550°C to 800°C. Next, it was measured how the specific resistance and resistance value variation of the semiconductor changed depending on the amount of Ba ₂ TiSi ₂ O ₈ added, and the results are shown in Table 1.

[Table] Table 1 also shows an example in which SiO ₂ is added as a semiconductor accelerator as in the conventional case. As is clear from Table 1, when the amount of Ba ₂ TiSi ₂ O ₈ added is in the range of 0.5 to 8.0%, the specific resistance is small and the variation in resistance value is low. If the amount added is less than 0.5%, it is difficult to promote semiconducting.
For this reason, the specific resistance is large and the variation in resistance values is also high. On the other hand, if it exceeds 8%, the firing specific gravity will decrease and the specific resistance will increase rapidly. By the way, in the case of conventional SiO ₂ -added products with the same specific resistance, for example, when comparing samples No. 8 and No. 3, there is a variation in the resistance value.
It is smaller when Ba ₂ TiSi ₂ O ₈ is added.
In addition, Ba ₂ TiSi ₂ O ₈ has a smaller change in resistivity with respect to the amount added and is more stable. Example 2 A BaTi ₃ -based positive characteristic ceramic semiconductor was produced using the same materials and methods as in Example 1, except that BaTiSi ₂ O ₇ was used as the semiconductor accelerator. Table 3 shows the measurement results of specific resistance and variation in resistance value with respect to the amount of BaTiSi ₂ O ₇ added.

[Table] As is clear from Table 3, the amount of BaTiSi ₂ O ₇ added is preferably 0.5 to 8.0% by weight. Example 3 A BaTiO ₃ -based positive characteristic ceramic semiconductor was produced using the same materials and method as in Example 1, except that BaSi ₂ O ₅ was used as a semiconductor accelerator. Table 4 shows the measurement results of specific resistance and variation in resistance value with respect to the amount of BaSi ₂ O ₅ added.

[Table] As is clear from Table 4, the amount of BaSi ₂ O ₅ added is
It can be seen that 0.5 to 8.0% by weight is preferable. In the present invention, Ba ₃ SiO ₅ , BaSi ₄ O ₉ ,
_{BaSi3O8 , Ba3SiO5 , BaSi2O5 , Ba2SiO4 ,}
Barium silicate compounds such as BaSiO ₃ and
Barium-titanium-silicate compounds such as BaTiSi ₃ O ₉ can also be used as semiconductor accelerators. In addition, in the above example, PbTiO 3 is added to control the point at which the resistance value of the PTC ceramic semiconductor suddenly increases (commonly known as the Tc point), but PbTiO ₃ is added instead.
It is known that SrTiO ₃ , BaSnO ₃ , BaZrO ₃ may be added, and Y ₂ O ₃ may be added as a semiconductor additive.
Although it is known that oxides such as Sb, Nb, and Ce may be added (Nb, Sb, Ta, Bi, <
La, Ce, Pr, Nd, Sm, Gd, Ho＞→ are rare earth elements). Therefore, these may be selected as appropriate. In summary, according to the present invention, when manufacturing a barium titanate-based positive characteristic ceramic semiconductor, 0.5 to 8.0 weight of a barium-titanium-silicate-based compound or a barium-silicate-based compound is added to the material as a semiconductor accelerator. % is added and fired, it is possible to reduce the variation in the resistivity of the PTC ceramic semiconductor and to lower the resistivity compared to the conventional case where SiO ₂ is used, for example.

Claims (1)

[Claims] _1. When _{manufacturing a} barium titanate _- based positive characteristic _ceramic semiconductor, _0.5 to _0.5 to Added 8.0% by weight,
A method for producing a positive characteristic ceramic semiconductor, which comprises firing.