Switching characteristics of MPB compositions of (Bi0.5Na0.5)TiO3–BaTiO3–(Bi0.5K0.5)TiO3 lead-free ferroelectric ceramics

The polarization switching characteristics of lead-free a(Bi0.5Na0.5)TiO3–bBaTiO3–c(Bi0.5K0.5)TiO3 (abbreviated as BNBK 100a/100b/100c) ferroelectric ceramics are investigated. For the first time, the strain hystereses of BNBK compositions inside and outside the morphotropic phase boundary (MPB) are presented. The total induced electrostrain (ε33,total) and apparent piezoelectric coefficient (d33) first increase dramatically and then decrease gradually as the BNBK composition moves from the tetragonal phase to the MPB and then to the rhombohedral phase. The measured polarization hystereses indicate that the BNBK compositions situated near the rhombohedral side of the MPB typically possess higher coercive field (Ec) and remanent polarization (Pr), while the compositions situated near the tetragonal side of the MPB possess higher apparent permittivity. BNBK 85.4/2.6/12 a composition well within the MPB, exhibits an ε33,total of ∼0.14%, an apparent d33 of 295 pCN−1 and a Pr of 22.5 μC cm−2. These property values suggest a candidate material for lead-free actuator applications.