Microstructure-PTCR Property Relationships in PbTiO₃-TiO₂ Ceramics

Abstract

Niobium doped PbTiO₃–TiO₂ ceramics show PTCR properties at the Curie temperature of PbTiO₃ (490°C). This paper describes the relationships between PTCR characteristics and the microstructure of PbTiO₃–TiO₂ ceramics. PTCR properties depend on the firing conditions that vary the microstructure of PbTiO₃–TiO₂ ceramics. The PTCR properties disappear when TiO₂ grains are connected each other from one end of the sample to the other. The resistivity–temperature characteristics of the interface between PbTiO₃ and TiO₂ grains are directly measured. It is found that PTCR characteristics are originated at the interface between PbTiO₃ and TiO₂ grains. On the basis of this idea, a new type of PTCR PbTiO₃–TiO₂ ceramics with the boundary layer structure is proposed.