JP3151566B2 - Barium titanate-based semiconductor material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a barium titanate-based semiconductor material having a low resistance and a high withstand voltage in a semiconductor ceramic (hereinafter abbreviated as a PTC element) having a positive temperature coefficient of electric resistance. Things.

[0002]

2. Description of the Related Art Barium titanate-based semiconductor materials are mainly composed of barium titanate, and Bi, S
It contains a trace amount of one or more of b, Ta, and rare earth elements, and has the characteristic of low specific resistance at room temperature and showing a remarkable positive resistance temperature change when the resistance exceeds a sudden change point (Curie point). are doing. By utilizing this characteristic, the PTC element is used as a temperature detecting element, a current limiting element, and the like. Conventionally, Ba atoms are replaced with Ca, S
By substituting with r and Pb atoms, respectively, the Curie point is moved to a high temperature side and a low temperature side while having a relatively large positive resistance temperature characteristic. And M
It is known that by including n, the specific resistance temperature change rate after exceeding the Curie point is increased, and furthermore, by including SiO ₂ , the specific resistance at room temperature is lowered and stable. It is known that

For example, Japanese Patent Publication No. Sho 63-28324 discloses that barium titanate is used as a main component and a part of barium is C
a, Sr and Pb, and Y, L
a, Ce and other rare earth elements are contained, and manganese is Mn.
0.03 to 0.10 mol% in terms of
There is disclosed a barium titanate-based semiconductor porcelain composition which is added and contained in an amount of 0.5 to 5 mol% in terms of ₂ , respectively. However, the specific resistance of the PTC element described in JP-B-63-28324 is as high as several tens of ohms. However, it is still not enough in terms of an increase in the resistance of the PTC material. For this reason, there is a demand for a material having a lower resistance, and a development of a well-balanced PTC material having a high withstand voltage. PTC
Although many proposals have been made to improve the characteristics of the element compared to the conventional one, the withstand voltage decreases as the specific resistance decreases, while the inconvenience of increasing the specific resistance increases the withstand voltage. Yes, the development of a balanced material has not yet been achieved.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a barium titanate-based semiconductor material having low resistance and high withstand voltage.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a barium titanate-based semiconductor porcelain comprising Ba, Ca, Sr, N
b, after wet mixing Si and Mn carbonate or oxide, the main component of calcined, obtained by baking, that Ba atoms were substituted 5-12 atomic% with 15-20 atomic% and Sr atoms Ca atoms with the composition, with respect to the main component composition, from 0.10 to 0.18 mol% in terms of niobium Nb ₂ O _5, 2.5 to 5 mol% in terms of silica on SiO _2,
And a barium titanate-based semiconductor material having a positive resistance temperature characteristic, which contains manganese in an amount of 0.07 to 0.10 mol% in terms of Mn.

In the barium titanate-based semiconductor porcelain used in the present invention, Ba atoms are 15 to 20 atomic% by Ca atoms .
And a main component composition substituted with 5 to 12 atomic% of Sr atoms.
As well as, with respect to the main component composition, the niobium Nb ₂
0.10 to 0.18 mol% in terms of O ₅ , silica is S
It contains 2.5 to 5 mol% in terms of iO ₂ and 0.07 to 0.10 mol% of manganese in terms of Mn. If the Ca atom content is less than 15 at%, the effect of increasing the withstand voltage is lost, while if it exceeds 20 mol%, the particles are uniformly miniaturized and the specific resistance increases. Nb ₂ O ₅ is added in an amount of 0.10 to 0.18.
Outside the range of mol%, the specific resistance increases. SiO ₂
When the addition amount is out of the range of 2.5 to 5 mol%, the specific resistance increases. Further, Mn is added in an amount of 0.07.
If the amount is less than 0.1 mol%, the withstand voltage decreases, while if it exceeds 0.1 mol%, the specific resistance sharply increases, which is not suitable for practical use because it does not meet the purpose of the present invention.

In the barium titanate-based semiconductor material of the present invention, part of Ba as the main component can be replaced with Pb, and part of Ti can be replaced with Sn or Zr.
The object of the invention can be achieved even if an excessive amount of titanium oxide is added.

[0008]

The present invention will be specifically described below with reference to examples and comparative examples. As starting materials, BaCO ₃ , Ca
CO ₃ , SrCO ₃ , PbO, TiO ₂ , Nb ₂ O ₅ ,
MnCO ₃ and SiO ₂ were prepared so as to have a predetermined ratio, mixed by a wet ball mill using zirconia balls for 18 hours, dried, and then calcined at 1150 ° C. for 2 hours. This calcined powder is pulverized, and polyvinyl alcohol is further
20% in diameter at a pressure of 1000 kg / cm ^{2 with} the addition of wt%
m and a disk having a thickness of 1.5 mm.

Next, it was fired at 1340 ° C. for about 1 hour. An Ag electrode having good ohmic contact was baked on the PTC ceramic thus obtained to obtain a PTC element. About this PTC element, specific resistance (ρ ₂₅ ) at normal temperature (25 ° C.), withstand voltage (V _B ),
The Curie point (Tc) was measured. Table 1 shows the raw material composition, and Table 2 shows the measurement results. Among the various characteristics described above, the withstand voltage characteristic is obtained by converting a voltage immediately before the element is destroyed due to a sudden increase in current value when a voltage is applied to the PTC element and gradually increased in voltage, per element thickness of 1 mm. The value was shown. Samples marked with an asterisk (*) in Tables 1 and 2 are outside the scope of the present invention, and all others are within the scope of the present invention. In the above examples, carbonates or oxides were used as starting materials. As is clear from Tables 1 and 2, the PTC element of each example has a greatly increased ratio of withstand voltage and specific resistance (V _B / ρ ₂₅ ) as compared with that of the comparative example. On the other hand, in the comparative example, the Ca substitution amount was 15 atomic%.
If it is less than 30, the effect related to high withstand voltage decreases, while C
When the substitution amount exceeds 20 atomic%, the specific resistance sharply increases. Ba atoms are 15 to 20 atomic% by Ca atoms.
Against substituted main component composition, the addition amount is 0.10 to 0.18 mol% of Nb ₂ O _5, SiO ₂ amount is 2.5
If the amount of 5 mol% and the amount of Mn are out of the range of 0.07 to 0.10 mol%, a PTC element having low resistance and high withstand voltage cannot be obtained. As described above, according to the present invention, the specific resistance of the PTC element can be reduced to 6 Ωcm or less, and the withstand voltage can be remarkably improved. The industrial effect is remarkable.

[0010]

[Table 1]

[0011]

[Table 2]

[0012]

According to the present invention, the amounts of Ca and Sr,
Further, by setting the amounts of Nb, Si and Mn in appropriate ranges, a PTC element having low resistance and high withstand voltage can be obtained. As a result, an element having a lower resistance can be manufactured for the same rated voltage, so that a current limiting element for a larger load can be put to practical use. Further, as the same resistance element, a thinner and smaller one can be practically used as compared with the conventional resistance element, so that an inexpensive element can be provided, and its use value is extremely high.

Continuation of the front page Judge, Naoto Noda Judge, Mitsuo Karato Judge, Toshiaki Yoshida (56) References JP-A-3-54165 (JP, A) JP-A-3-88770 (JP, A) JP-A 52- 20291 (JP, A)

Claims (1)

(57) [Claims] In a barium titanate-based semiconductor porcelain, Ba, Ca, Sr, Nb, Si and Mn carbonates or oxides are wet-mixed , then calcined and calcined, and Ba atoms are obtained by Ca atoms. 15-20 atomic% and Sr
The main component composition was replaced with 5 to 12 atomic% of atoms. Niobium was converted to Nb ₂ O ₅ in an amount of 0.10 to 0.18 mol%, and silica was converted to SiO ₂ with respect to the main component composition. A barium titanate-based semiconductor material having a positive resistance temperature characteristic, comprising 2.5 to 5 mol% in terms of Mn and 0.07 to 0.10 mol% in terms of Mn of manganese.