Microstructure and electrical properties of BaTiO3-(Bi0.5M0.5)TiO3 (M=Li, Na, K, Rb) ceramics with positive temperature coefficient of resistivity

Abstract

Lead-free 0.912Ba0.97TiO3-0.088(Bi0.5M0.5)TiO3 (M=Li, Na, K, Rb) ceramics with positive temperature coefficient of resistivity (PTCR) were prepared by conventional solid sintering reaction using high-purity reagents of metal oxides and carbonates. The effect of (Bi0.5M0.5)TiO3 (M=Li, Na, K, Rb) doping on the microstructure and electrical properties of the samples were investigated. X-ray diffraction analysis indicated that all the samples were of a single perovskite structure with tetragonal phase, and the calculated c/a value increased first and then decreased. The Raman shift at 305cm−1 became strong first and then declined when M in the dopant (Bi0.5M0.5)TiO3 was changed from Li to Rb. The Curie temperature of the samples displayed a tendency to increase first and then decrease, in which BaTiO3-(Bi0.5K0.5)TiO3 ceramics presented the highest value. Moreover, after the incorporation of alkali ions, the PTCR value (defined by the resistivity jump with the ratio of the maximum to minimum) and room temperature resistivity of the samples decreased first and then increased, in which BaTiO3-(Bi0.5Na0.5)TiO3 ceramics possessed the lowest room temperature resistivity.