Phase transition and electrical properties of (1-x)K_(0.5)Na_(0.5) NbO_3-xBi_(0.5)Na_(0.5)Zr_(0.8)Ti_(0.2)O_3 lead-free piezoceramics

摘要

A new system of (1-x)K_(0.5)Na_(0.5)NbO_3-xBi_(0.5)Na_(0.5)Zr_(0.8)Ti_(0.2)O_3 [KNN-xBNZT] lead-free piezoelectric ceramics has been prepared by the conventional solid state sintering method. Systematic investigations on the microstructure, crystalline structure as well as dielectric, piezoelectric and ferroelectric properties were carried out. The ceramics have a coexistence of orthorhombic and tetragonal phases near room temperature. Remarkably strong piezoelectricity of d_(33)=280 pC/N and k_p=38.8% has been obtained in the KNN-0.04BNZT ceramic, together with a high T_C of 342 °C. It was considered that the observed strong piezoelectricity might be primarily ascribed to its orthorhombic-tetragonal phase transition near room temperature.