Effects of nano-sized BiFe[O.sub.3] addition on the properties of high piezoelectric response [Bi.sub.0.5][Na.sub.0.5]Ti[O.sub.3]-x[Bi.sub.0.5][K.sub.0.5]Ti[O.sub.3] ceramics

The role of BiFe[O.sub.3] addition on the crystal structure, microstructure, and the electrical and electromechanical properties of high-sensitivity [Bi.sub.0.5][Na.sub.0.5]Ti[O.sub.3]-[Bi.sub.0.5][K.sub.0.5]Ti[O.sub.3] ferroelectric ceramics for compositions at the morphotropic phase boundary (MPB) is investigated. A perovskite solid solution from nano-sized BiFe[O.sub.3] and [Bi.sub.0.5][Na.sub.0.5]Ti[O.sub.3]-[Bi.sub.0.5][K.sub.0.5]Ti[O.sub.3] powders is obtained, in which the persistence of a MPB in the ternary system is demonstrated. The structural characterization, along with the electrical properties, indicates the stabilization of intermediate domain configurations, associated with a decrease of the temperature for the development of the ferroelectric long-range order. As a consequence, high phase-change electromechanical response is found for certain small BiFe[O.sub.3] additions. This result is very promising for the processing of textured ceramics taking advantage of the decomposition behaviour of BiFe[O.sub.3]. Ceramic texturing is demonstrated, a key technology for developing lead-free piezoelectrics that can replace Pb(Zr, Ti)[O.sub.3].