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

The crystal structure and piezoelectric properties of ternary ceramics x(Bi1/2Na1/2)TiO3-y(Bi1/2K1/2)TiO3-zKNbO(3) (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 d(33)=215 pC/N which reached a maximum value in this ternary system and planar electromechanical coupling factor k(p)=35%. Besides, BNT-BKT-KN87/10/3 ceramics had good performances with piezoelectric constant d(33)=138 pC/N and electromechanical coupling factor k(p)=38% which attained a maximum value in this ternary system. (c) 2007 American Institute of Physics.