Effect of SiO2 sintering additive on the positive temperature coefficient of resistivity (PTCR) behavior of (Bi1/2Na1/2)0.10Ba0.90TiO3 + CaO ceramics

Lead-free (Bi1/2Na1/2)(0.10)Ba0.90TiO3 ceramics with 3.5 mol% CaO addition and positive temperature coefficient of resistivity (PTCR) behavior were prepared by the mixed-oxide route. Nanocrystalline TiO2 powder is required as raw material to allow complete phase formation during calcination at 800 degrees C. Samples were sintered at T < 1250 degrees C in air to give thermistor ceramics with low room-temperature resistance and significant rise of resistivity at T-c = 155 degrees C. The microstructure formation and electrical properties are sensitive to silica addition. Dense PTCR thermistor ceramics with low room-temperature resistivity rho(RT) = 80 Omega cm and resistivity change rho max/rho min over two orders of magnitude at the Curie temperature were obtained after sintering in air with 0.05 wt% Sio(2) sintering additive. (C) 2017 Elsevier Ltd. All rights reserved.