Sb5+ Modified Phase Transition in (Li, Na, K)(Nb1-xSbx)O3 Piezoelectric Ceramics
The modified behavior of the phase transition temperatures (TO-T and/or TC) between orthorhombic (O), tetragonal (T) and cubic (C) that caused by doping Sb5+ in (Li0.052Na0.493K0.455)(Nb1-xSbx)O3 (LNKNSx) ceramics was reported in the present investigation. The results show that differing from the insensitive TO-T to the Sb5+ content, TC splits into two peaks TCI and TCII when doping Sb5+. The decreased TCI by raising x may be ascribed to the Sb-rich grains and the settled TCII round 480 °C resulting from the Sb-lack ones. The enhanced piezoelectric coefficient d33 value of 263 pC/N and planar mode electromechanical coupling coefficient kp value of 42.5% at x=0.052 can be attributed to the polymorphic phase boundary (PPB) behavior with an appropriate ratio between T and O phases without any second phase.