Bi4Ti3O12-Based Piezoelectric Ceramics for High Temperature Applications

Abstract

High temperature piezoelectric ceramics based on WO3-doped Bi4Ti3O12 (W-BIT) were prepared by two ways: chemical (hydroxide coprecipitation) and conventional oxides mixing. Sintering was carried out between 800 degrees -1150 degreesC in air. A rapid densification, >99% rho (th) at 900 degreesC/2h, took place in the coprecipitated W6+-doped BIT ceramics, whereas conventionally prepared BIT-based materials achieved only a maximum density of -94% rho (th), at 1050 degreesC. As expected, a plate-like morphology in both materials appeared, with the aspect ratio (1/t) of the grains increasing linearly with the sintering temperature. Plate-like grains were larger in the conventionally prepared W-BIT based materials. The sintering behaviour could be related both with the agglomeration state of the calcined powders and with the enlargement of the platelets at high temperature. The W6+-doped BIT materials showed an electrical conductivity value 2-3 orders of magnitude lower than undoped samples. The most important result of the electrical characterisation of this type of materials was that the electrical conductivity increased exponentially with the aspect ratio (1/t) of the plate-like grains.