Effect of SiO2 sintering aids on high critical temperature positive temperature coefficient of resistivity properties of (Pb0.6Sr0.3Ba0.1)TiO3 materials prepared by microwave sintering technique

Positive temperature coefficient of resistivity (PTCR) materials with the composition (Pb0.6Sr0.3Ba0.1)TiO3, possessing a high critical temperature as T-c = 420 degrees C, have been prepared by microwave sintering technique. Incorporation of SiO2 as sintering aids has lowered the sintering temperature (soaking time) required from 1250 degrees C (10 min) to 1140 degrees C (10 min), where the core-shell microstructure was fully developed. The electrical properties were stabilized for the samples containing more than 5 mol% SiO2 and sintered at a temperature higher than 1120 degrees C (10 min). The resistivity ratio, PTCR jump and minimum resistivity achieved are (rho(max)/rho(min))approximate to 10(2.85)-10(3.2) Omega . cm, PTCR=0.026-0.030 and rho(min)approximate to 10(2) Omega . cm, respectively. The corresponding energy level of the donors (Y+3-ions) and the effective electron traps (cationic vacancies) are estimated to be epsilon(d) = 0.077 eV and epsilon(a) = 0.67 eV + epsilon(F), respectively, where epsilon(F) is the Fermi level of the materials. The electronic parameters, such as donor level (epsilon(d)), PTCRjump and trap level (epsilon(a)), are better parameters for indicating the perfectness of the densification process than the crystal structural and the microstructural examinations.