Morphotropic phase boundary and piezoelectric properties of (Bi1∕2Na1∕2)TiO3–(Bi1∕2K1∕2)TiO3–KNbO3 lead-free piezoelectric ceramics

Abstract

The crystal structure and piezoelectric properties of ternary ceramics x(Bi1∕2Na1∕2)TiO3–y(Bi1∕2K1∕2)TiO3–zKNbO3 (abbreviated as BNT-BKT-KN100x∕100y∕100z) system have been investigated. Effects of BKT and KN on the crystalline structure were examined. The morphotropic phase boundary (MPB) phase diagram of BNT-BKT-KN ternary system was determined by x-ray diffraction patterns from sintered specimens. Near the MPB, BNT-BKT-KN82∕16∕2 ceramics had good performances with piezoelectric constant d33=215pC∕N which reached a maximum value in this ternary system and planar electromechanical coupling factor kp=35%. Besides, BNT-BKT-KN87∕10∕3 ceramics had good performances with piezoelectric constant d33=138pC∕N and electromechanical coupling factor kp=38% which attained a maximum value in this ternary system.