JPH02192457A - Semiconductor ceramic - Google Patents

Abstract

PURPOSE:To obtain a semiconductor ceramic having low specific resistance at room temperature and high temperature coefficient by adding TiO, SiO2, MnO2 and Al2O3 to a barium titanate material containing semiconductive element and Ca substituting Ba. CONSTITUTION:The objective ceramic is a barium titanate semiconductor ceramic containing semiconductive element, containing 13-17atom% of calcium substituting the barium of the barium titanate. and further containing 0.5-1.5mol% of TiO2, 0.4-0.5mol% of SiO2, 0.01-0.03mol% of MnO2 and 0.2-0.3mol% of Al2O3. The semiconductive element used in the above ceramic is Sb, Bi, Nb, Ta or rare-earth elements. The amount of the semiconductive element depends upon the kind of the element and is about 0.1-0.5atom% in the case of yttrium. A part of barium of barium titanate may be substituted with strontium to vary the Curie temperature of the semiconductor ceramic.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to semiconductor porcelain with a positive temperature coefficient.

[Background of the invention]

Barium titanate-based semiconductor ceramic materials utilize their positive temperature coefficients and are used in various applications such as overcurrent protection, temperature control, and heaters. Among these, recently, low-resistance thermistor elements are expected to be used for preventing overcurrent in automobile motors and for preventing overheating of electronic components. By the way, in order to improve the response of the thermistor element, it is important to make the thermistor element small and to have its resistance change rapidly due to changes in temperature or current. For this reason, a material with a low specific resistance at room temperature and a large temperature coefficient is required. Until now, attempts have been made to replace barium in barium titanate-based semiconductor ceramic materials with calcium in order to reduce the specific resistance at room temperature. It has come to be praised as. In addition, in order to increase the positive temperature coefficient,
Publication No. 77 claims that a temperature of 16%/°C or higher was obtained by adding sodium. However, with conventional barium titanate-based semiconductor ceramic materials, as the resistivity decreases, the temperature coefficient also decreases, and the room temperature resistivity must be 10 Ω・em or less and the temperature coefficient must be 10%/℃ or higher. I haven't been able to do that. For example, although the specific resistance at room temperature is small in Japanese Patent Publication No. 54-10110, there is a problem with the temperature coefficient.
Although the temperature coefficient of JP 21877 is large, the specific resistance at room temperature is a problem.

[Disclosure of the invention]

An object of the present invention is to provide a semiconductor ceramic material that has a low room temperature resistivity and a high temperature coefficient. The object of the present invention is to provide barium titanate-based semiconductor porcelain containing a semiconducting element, in which barium in the barium titanate is replaced with calcium, and the amount of calcium atoms is 13 to 17 atoms. %, and further 0.5 to 1.5 mol% Tidy, 0.4 to 0.5
mol% SiO□, 0.01-0.03 mol% MnO
2, and 0.2-0.3 mol%^! 20. This is achieved by a semiconductor porcelain characterized by containing. In addition, in the above-mentioned semiconductor porcelain, as the semiconductor element, one or more selected from the group of Sb, Bi, Nb, Ta or rare earth elements can be selected as appropriate, and the content of these semiconductor elements is determined according to these elements. It cannot be determined unambiguously because it depends on the type of element, but for example, in the case of using yttrium, it is about 0.1 to 0.
The amount is about 5 atomic %, and a part of barium in barium titanate may be replaced with strontium in order to change the Curie temperature of semiconductor ceramics.

【Example】

BaCO5,5rCOs, CaCL, T as starting materials
A predetermined amount of i(h, Y, 05.5iOz, MnO2, ^I20.) was weighed to have the composition shown in Table 1, and this was wet mixed for 20 to 40 hours using a polyethylene bot mill and a resin-coated ball. and then dry it for 1
Calculate at 100°C for 4 hours. Next, this calcined material is pulverized, polyvinyl alcohol is added as a binder, and the powder that has passed through a 150 μm mesh filter is formed into a powder having a diameter of 12.5 mm and a thickness of 1. It was formed into a disk shape and fired for 0.2 to 3 hours at a temperature of 1300 to 1380°C. In-Ga alloy was attached to both sides of the barium titanate-strontium titanate semiconductor ceramic material thus obtained. , room temperature resistivity, and temperature coefficient were determined, and these are shown in Table 1. Furthermore, the temperature coefficient α is a = (lnR2-InR+>/(T 2 T
+) As can be seen from Table 1, the semiconductor ceramic material of the present invention has a small resistivity and a large temperature coefficient.On the other hand, titanic acid with a calcium substitution amount of 10 atomic % or less or 20 atomic % or more Barium-strontium titanate-based materials have a large specific resistance;
Barium titanate with 7 atom% substituted with calcium
Even with strontium titanate-based materials, TiO2
, 5iOz, MnL, ^1□0. If the content is too high or too low, the temperature coefficient becomes small.
13 to 17 at% of the total amount of barium and strontium
The excess TiO2 contained in the barium titanate-strontium titanate material in which is replaced with calcium is 0.
．． 5-1.5 mol%, excess SiO2 is 0.4-0.5
mol%, excess MnO2 is 0.01-0.03 mol%,
Excessive ^! 20. It is important that the amount is 0.2 to 0.3 mol%.

【effect】

The semiconductor porcelain according to the present invention is a barium titanate-based semiconductor porcelain containing a semiconducting element, in which barium in the barium titanate is replaced with calcium,
Moreover, the amount of calcium atoms is 13 to 17 atomic %, and 0.5 to 1.5 mol % of Ties, 0.4 to 17 atomic %.
Since it contains 0.5 mol% of 5ift, 0.01 to 0.03 mol% of MnO2, and 0.2 to 0.3 mol% of Al2O3, this material has a low room temperature specific resistance, and Since it is a semiconductor material with a large positive temperature coefficient, it has the advantage of being suitable for use as a thermistor element for preventing overcurrent in automobile motors or overheating of electronic components, for example. Patent applicant Chichibu Cement Co., Ltd.

Claims (3)

[Claims] (1) A barium titanate-based semiconductor porcelain containing a semiconducting element, in which barium in the barium titanate is replaced with calcium, and the amount of calcium atoms is 13 to 17 at%, Further 0.5-1
．． 5 mol% TiO_2, 0.4-0.5 mol% Si
A semiconductor ceramic characterized by containing O_2, 0.01 to 0.03 mol% MnO_2, and 0.2 to 0.3 mol% Al_2O_3. (2) In the semiconductor ceramic according to claim 1, the semiconductor element is one or more selected from the group of Sb, Bi, Nb, Ta, or rare earth elements. (3) The semiconductor porcelain according to claim 1, in which barium in barium titanate is replaced with strontium.