Phase transition, microstructure and electrical properties of Fe doped Ba0.70Ca0.30TiO3 lead-free piezoelectric ceramics.

Lead-free piezoelectric ceramics of Ba0.70Ca0.30Ti1−x Fe x O3 (x=0–0.03) have been synthesized by a conventional solid state reaction method. The influence of Fe content on the microstructure, phase transition, dielectric, ferroelectric, and piezoelectric properties is investigated systematically. The ceramics with x≤0.02 are diphasic composites of tetragonal Ba0.80Ca0.20TiO3:Fe and orthorhombic Ba0.07Ca0.93TiO3:Fe solid solutions. The tetragonal phase is gradually suppressed as x increases, the ceramic with x=0.03 is found to have diphasic pseudocubic and orthorhombic phases. And the grain size is dependent on Fe content significantly. Introduction of Fe at B-sites improves the densification and decreases the sintering temperature. As x increases from 0 to 0.03, the room temperature relative dielectric permittivity enhances, dielectric loss decreases, and the Curie temperature decreases monotonically from 128°C to 58°C. However, the ferroelectricity enhances slightly and reaches the maximum near x=0.005, and then weakens with increasing x. On the other hand, the piezoelectric coefficient (d 33) and the electromechanical coupling coefficient (k p ) decrease simultaneously with increasing x, whereas the mechanical quality factor (Q m ) increases significantly. The structure–electrical properties relationship is discussed intensively to give more information on (Ba,Ca)TiO3-based lead-free piezoelectric ceramics. [ABSTRACT FROM AUTHOR]