Effect of Bi 2O 3 doping methods on the positive temperature coefficient property of Ba 0.999(Bi 0.5Na 0.5) 0.001TiO 3 ceramics

Abstract

Lead-free positive temperature coefficient of resistivity ceramics based on 0.999BaTiO 3–0.001(Bi 0.5Na 0.5)TiO 3 solid solution were fabricated by the conventional ceramic technique, while Bi 2O 3 was doped directly or after pre-calcining, in the molar ratio of Bi 2O 3:Na 2CO 3:TiO 2 ( G) = 1:1:4, 1.005:1:4, 1.01:1:4, and 1.015:1:4, respectively. There are two synthesizing route, i.e. the materials with G = 1.005:1:4 were pre-calcined at 780 °C firstly and then doped into the basic materials and the materials were directly doped by G = 1.01:1:4 into the starting materials with another holding process at 850 °C for 30 min during co-calcining with BaTiO 3, both of which could obtain samples with the maximum Curie temperature about 144 °C. The latter also possessed comparatively lower room temperature resistance about 22.0 Ω. A further study was deserved to carry out in an attempt to obtain ceramics with higher Curie temperature via more Bi 2O 3-doping.