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 0.912Ba 0.97 TiO 3 -0.088(Bi 0.5 M 0.5 )TiO 3 (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 (Bi 0.5 M 0.5 )TiO 3 (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 305 cm −1 became strong first and then declined when M in the dopant (Bi 0.5 M 0.5 )TiO 3 was changed from Li to Rb. The Curie temperature of the samples displayed a tendency to increase first and then decrease, in which BaTiO 3 -(Bi 0.5 K 0.5 )TiO 3 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 BaTiO 3 -(Bi 0.5 Na 0.5 )TiO 3 ceramics possessed the lowest room temperature resistivity.