Abstract
Positive temperature coefficient of resistivity (PTCR) materials with the composition (Pb 0.6 Sr 0.3 Ba 0.1 )TiO 3 , possessing a high critical temperature as T e = 42O°C, have been prepared by microwave sintering technique. Incorporation of SiO 2 as sintering aids has lowered the sintering temperature (soaking time) required from 1250°C (10min) to 1140°C (10min), where the core-shell microstructure was fully developed. The electrical properties were stabilized for the samples containing more than 5mol% SiO 2 and sintered at a temperature higher than 1120°C (10min). The resistivity ratio, PTCR jump and minimum resistivity achieved are (ρ max /ρ min )≈10 2.85 -10 3.2 Ω·cm, PTCR=0.026-0.030 and ρ min ≈10 2 Ω·cm, respectively. The corresponding energy level of the donors (Y +3 -ions) and the effective electron traps (cationic vacancies) are estimated to be ε d = 0.077 eV and ε a = 0.67 eV+ε F , respectively, where ε F is the Fermi level of the materials. The electronic parameters, such as donor level (ε d ), PTCR jump and trap level (ε a ), are better parameters for indicating the perfectness of the densification process than the crystal structural and the microstructural examinations.