INFLUENCE OF SINTERING PROFILE ON THE RESISTIVITY OF LOW-CURIE-POINT PTCR CERAMICS

The influence of sintering profile, with emphasis on the effect of soa king treatment and cooling rate, on the resistivity of low-Curie-point positive temperature coefficient of resistivity (PTCR) ceramics has b een investigated. Soaking treatment at 1200-degrees-C or slower coolin g rate were found to result in an increase in the room-temperature and maximum values of resistivity in the resistivity-temperature characte ristics. The surface acceptor density (N(s)), whose value was extracte d from the capacitance-voltage measurement, was found to increase with soaking treatment at 1200-degrees-C or slower cooling rate. From deri vations based on the Heywang-Jonker model, higher room-temperature and maximum resistivities are expected to occur as a result of increasing N(s), as confirmed by the experimental data.