Enhanced Piezoelectric Properties of Lead-Free La and Nb Co-Modified Bi-0.5(Na0.84K0.16)(0.5)TiO3-SrTiO3 Ceramics

New lead-free piezoelectric ceramics 0.96[{Bi-0.5(Na-0.84 K-0.16)(0.5)}(1-x)La-x(Ti1-y Nb-y)O-3]-0.04SrTiO(3) (BNKT-ST-LN, where x = y = 0.00 <= (x = y) <= 0.015) were synthesized using the conventional solid-state reaction method. Their crystal structure, microstructure, and electrical properties were investigated as a function of the La and Nb (LN) content. The X-ray diffraction patterns revealed the formation of a single-phase perovskite structure for all the LN-modified BNKT-ST ceramics in this study. The temperature dependence of the dielectric curves showed that the maximum dielectric constant temperature (T-m) shifted towards lower temperatures and the curves became more diffuse with an increasing LN content. At the optimum composition (LN 0.005), a maximum value of remnant polarization (33 C/cm(2)) with a relatively low coercive field (22 kV/cm) and high piezoelectric constant (215 pC/N) was observed. These results indicate that the LN co-modified BNKT-ST ceramic system is a promising candidate for lead-free piezoelectric materials.