Compositional analysis and electrical properties of Sb, Mn-doped barium strontium titanate PTCR ceramics with TiO<inf>2</inf>and SiO<inf>2</inf>sintering additives

Abstract

The secondary phase compositions in Sb-doped (Ba, Sr)TiO3ceramics containing SiO2and excess TiO2sintering additives have been examined by XRD, BEI and EPMA techniques. It is shown that alongside the primary (Ba0.797Sr0.2Sb0.003) TiO3phase, (Ba1.95Sr0.05)2(Ti1.2Si1.8)O8and Sb-doped (Ba0.99Sr0.01)6Ti17O40phases form at the intergranular regions. Substitution of up to 0.04 mol% MnO2enhances the PTCR effect, giving a ratio ρmax/ ρmin∼ 7 × 105for the optimum 0.04% MnO2composition. At this level Mn cannot be detected in the microstructure by EPMA, however in insulating samples containing 0.08 mol% of MnO2, it was detected in the (Ba0.99Sr0.01)6Ti17O40intergranular phase. © Springer Science+Business Media, LLC 2007.