The thermal sensitivity and dielectric properties of SrTiO 3-based ceramics

Abstract

The thermal sensitivities of SrTiO 3-based ferroelectric ceramics and the dielectric properties have been investigated. Strontium–lead titanate ceramics with variable NTCR–PTCR composite effect were prepared by controlling Pb concentration of the grain boundaries. It was efficient for lowering the room temperature resistivity ( ρ RT) and weakening the negative temperature coefficient of resistance (NTCR) effect of (Sr, Pb)TiO 3 ceramics by adding a small amount of excess PbO. A transformation of thermal sensitivity from the positive temperature coefficient of resistance (PTCR) to NTCR–PTCR characteristics was also observed after a heating treatment process, showing the NTCR–PTCR composite effects of (Sr, Pb)TiO 3 semiconducting ceramics were closely related to the variation of Pb concentration at the grain boundaries. The conduction mechanism was proposed to reasonably explain the NTCR–PTCR composite effect of (Sr, Pb)TiO 3 semiconducting ceramics. SrTiO 3 ceramics capacitors were fabricated by using La 2O 3–CuO–PbO as dopants. It exhibited a high dielectric constant with stable temperature characteristics. It was found that PbO addition benefited to increasing the dielectric constant and CuO addition mainly segregated at the grain boundaries to form the isolation layers. The relationships between the microstructures and the dielectric properties of SrTiO 3–La 2O 3–CuO–PbO system were discussed.