RAW MATERIAL COMPOSITION FOR POSITIVE TEMPERATURE COEFFICIENT THERMISTOR, PORCELAIN FOR POSITIVE TEMPERATURE COEFFICIENT THERMISTOR, AND PRODUCTION OF ITS PORCELAIN

摘要

PROBLEM TO BE SOLVED: To provide a porcelain for a positive temperature coefficient thermistor having a specific resistance at the room tem. of <=5 Ω.cm, a static withstand voltage of >=60 V/mm, a temp. coefficient of resistance of >=9.0 %/ deg.C and exhibiting little dispersion in the resistance. SOLUTION: A raw material composition contains, as main components(total 100 mol.%), 30-97 mol.% BaTiO3, 1-50 mol.% PbTiO3, 1-30 mol.% SrTiO3 and 1-25 mol.% CaTiO3 and further contains samarium oxide of 0.1-0.3 mol expressed in terms of Sm atom, manganese oxide of 0.01-0.03 mol expressed in terms of Mn atom and silicon oxide of 0-2.0 mol expressed in terms of Si atom, each being based on 100 mol of the total amount of the main components. The porcelain is obtained by firing the raw material composition, preferably, under a neutral atmosphere or a reductive atmosphere and then heat-treating the fired composition under an acidic atmosphere.