Morphotropic phase boundary in the BNT-BT-BKT system

Lead-free x Bi0.5Na0.5TiO3-y BaTiO3-z Bi0.5K0.5TiO3 piezoelectric ceramics were synthesized by a conventional solid state reaction method. The microstructure, ferroelectric and piezoelectric properties of the ceramics were investigated. Structure measurements by X-ray diffraction with Rietveld refinement have allowed us to specify more precisely the morphotropic phase boundary (MPB) in this system. For (1 - x) BNT-x BT solid solution ceramics, the 0.94 BNT-0.06 BT morphotropic composition shows the higher values with d(33) = 170 pC/N, k(p) = 0.35 and k(t) = 0.53. In the case of (1 - x) BNT-x BKT compositions, the d(33), k(p) and k(t) are, respectively, 137 pC/N, 0.39 and 0.54 for the 0.80 BNT-0.20 BKT ceramic. On the other hand, the ternary 0.865 BNT-0.035 BT-0.100 BKT morphotropic composition shows high piezoelectric constant and electromechanical coupling factors (d(33) = 133 pC/N, k(p) = 0.26 and k(t) = 0.57). (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.