Effect of ZnO on the structure, microstructure and electrical properties of KNN-modified piezoceramics

The effects of ZnO addition on structure, microstructure and dielectric properties of (K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O-3 ceramics (KNL-NTS) are investigated. Doping provokes phase segregation, evidenced by the appearance of different types of grains and a tetragonal tungsten-bronze secondary phase at high ZnO doping levels. A clear increase of ferroelectric-paraelectric and orthorhombic-to-tetragonal phase transition temperatures with ZnO content is observed. This produces a reduction of the room temperature piezoelectric constants due to the reduction of the tetragonality (cla) ratio of the KNL-NTS structure. (C) 2009 Elsevier Ltd. All rights reserved.