Preparation of PTC Ceramic Material of Over-cruuent Limiter for Program-controlled Telephone Exchanger

High performance PTC ceramic material with low resistivity is desired to prepare an over-current limiter for program-controlled telephone exchanger. In this paper, it is described that PTC ceramic material based on (Ba-Sr-Ph)TiO3 solid solution has been obtained with Curie Point of 90°C, resistivity at room temperature of 30fi'cm and resistivity jump 105 by means of selection of raw materials, several additive modification and special sintering procedure, and the related element can be successfully used asan over-current limiter for program- controlled telephone exchanger.