Morphotropic phase boundary and piezoelectric properties of (Bi_(1/2)Na_(1/2))TiO_3-(Bi_(1/2)K_(1/2))TiO_3-KNbO_3 lead-free piezoelectric ceramics

摘要

The crystal structure and piezoelectric properties of ternary ceramics x(Bi_(1/2)Na_(1/2))TiO_3-y(Bi_(1/2)K_(1/2))TiO_3-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.