Phase structure and electrical properties of Yb and Mn co-substituted (K0.48Na0.52)NbO3 lead-free piezoelectric ceramics

Rare-earth and Mn co-substituted KNN-based lead-free piezoelectric ceramics and (1-x)(K0.48Na0.52)-NbO3- xYbMnO(3) (KNN-xYM) were prepared by a conventional solid-state sintering method. The effects of YM addition on the structure, dielectric, and piezoelectric properties of KNN-xYM ceramics were systematically investigated. With increase of YM content, from the rhombohedral to orthorhombic transition temperature (TR-O) moves close to room temperature against the direction of the orthorhombic to tetragonal transition temperature (TO-T). A polymorphic phase transitions (PPT) between rhombohedral and orthorhombic phases exists at x similar to 0.01 and the optimum electrical characterization (d(33) similar to 140 pC/N, k(p) similar to 0.42, Q(m) similar to 214, epsilon(r) similar to 634, tan delta similar to 0.02, and Tc similar to 386 degrees C) is also given to the compositions (x = 0.01) around PPT. In addition, KNN-xYM ceramics became a relaxor ferroelectric gradually with increasing YM content. These results indicate that the enhanced piezoelectric properties can be achieved based on the coexistence of rhombohedral and orthorhombic phases. (C) 2013 Elsevier B. V. All rights reserved.