Morphotropic phase boundary in the BNT-BT-BKT system

摘要

Lead-free x Bi_(0.5)Na_(0.5)TiO_(3-y) BaTiO_(3-z) Bi_(0.5)K_(0.5)TiO_3 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).