Microstructure and electrical properties of porous (Ba,Sr)TiO3 ceramics

Porous and fine-grained (Ba,Sr)TiO3 ceramics were fabricated by the addition of partially oxidized Ti or Ti powders into the (Ba,Sr)TiO3 powders. The crystalline structure of the porous (Ba,Sr)TiO3 ceramics was strongly dependent on the oxygen contents. The room-temperature crystalline structure of the vacuum-sintered (Ba,Sr)TiO3 was cubic, while that of the vacuum-sintered and then paste-baking treated (Ba,Sr)TiO3 was tetragonal. The paste-baking treated (Ba,Sr)TiO3, containing 5–7 vol.% partially oxidized Ti, showed the excellent positive temperature coefficient of resistivity (PTCR) characteristics.