Morphotropic phase boundary in the BNT–BT–BKT system

Abstract: 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 =170pC/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, 137pC/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 =133pC/N, k p =0.26 and k t =0.57). [Copyright &y& Elsevier]