Nature of polar state in 0.67BiFeO 3 –0.33BaTiO 3

This study was conducted to understand the nature of the polar state in the morphotropic phase boundary composition 0.67BiFeO3–0.33BaTiO3 (0.67BF–0.33BT). Both the unpoled and poled specimens exhibit an average cubic structure. The poling induces a 0.14% increase in the lattice parameter. Macrodomains are absent both in the initial and polar state of 0.67BF–0.33BT. A typical relaxor-type dielectric anomaly was observed (Tf = ~ 627 K, TB = ~ 820 K). The remnant polarization (Pr), maximum value of electrostrain (Sm), and magnitude strain at Ec in the bipolar mode (Sneg) increase clearly during heating (Pr, ~ 40 µC/cm2; Sm, 0.191% under 40 kV/cm at 453 K). Unlike Bi0.5Na0.5TiO3-based nonergodic relaxors, the first-cycle bipolar electrostrain loops indicate that the minimum strain on the negative side of the bipolar strain curves is negative. Furthermore, the slopes of the relative permittivity versus log frequency plots in unpoled (− 21) and poled (− 23) specimens are similar. The transition between the relaxor state and ferroelectric-like state does not involve a clear dielectric anomaly even in the poled specimen.