Comparison of structural, ferroelectric, and piezoelectric properties between A-site and B-site acceptor doped 0.93Bi0.5Na0.5TiO3-0.07BaTiO3 lead-free piezoceramics

Abstract The effects of A-site Li- or B-site Fe-doping into 0.93(Bi0.5Na0.5)TiO3-0.07BaTiO3 (BNBT) ceramics were systematically investigated for the compositional ranges of (Bi0.465Na0.465Ba0.07)1-xLixTiO3 (BNBT-xLi) and (Bi0.465Na0.465Ba0.07)FexTi1-xO3 (BNBT-xFe) (x = 0.01–0.03). The R3c/P4bm phase ratio remained essentially unchanged across the entire set of Li and Fe doping levels studied. Although some typical characteristics for acceptor doping were observed for both BNBT-xLi and BNBT-xFe, their ferroelectric and piezoelectric properties were different. A clear transition from a slim (BNBT, Ec = 17.0 kV/cm, Pr = 22.9 μC/cm2) to square-like P-E hysteresis loops (Ec = 30.7 kV/cm, Pr = 33.9 μC/cm2) was observed in BNBT-xLi at x≥0.02. In contrast, constricted P-E loops (Ec = 13.5–15.1 kV/cm and Pr = 28.6–31.7 μC/cm2) and deformed butterfly S-E curves were detected in all BNBT-xFe ceramics. These results suggest A-site Li doping as a more effective method for stabilizing the non-ergodic relaxor phase in BNT-BT ceramics, which could help further tailor the piezoelectric properties in other A-site doped Bi-based perovskite systems.