Effect of SiO 2 Sintering Aids on High Critical Temperature Positive Temperature Coefficient of Resistivity Properties of (Pb 0.6Sr 0.3Ba 0.1)TiO 3 Materials Prepared by Microwave Sintering Technique

Abstract

Positive temperature coefficient of resistivity (PTCR) materials with the composition (Pb0.6Sr0.3Ba0.1)TiO3, possessing a high critical temperature as T c=420° C, have been prepared by microwave sintering technique. Incorporation of SiO2 as sintering aids has lowered the sintering temperature (soaking time) required from 1250° C (10 min) to 1140° 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° C (10 min). The resistivity ratio, PTCR jump and minimum resistivity achieved are (ρmax /ρmin )≈102.85–103.2 Ω· cm, PTCR=0.026–0.030 and ρmin ≈102 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.