Ferroelectric Properties and Domain Structures of (Bi_0.5K_0.5)TiO₃-BiFeO₃ Ceramics

Abstract

  Crystal structures and dielectric, polarization, and piezoelectric properties of x(Bi_0.5K_0.5)TiO₃-(1−x)BiFeO₃ ceramics were investigated. The results obtained using x-ray and neutron powder diffractions show that a morphotropic phase boundary between the rhombohedral (ferroelectric) and pseudo-cubic (ferroelectric) phases is present in 0.4 ＜ x ＜ 0.43. Ceramics with x = 0.4 exhibited a large remanent polarization of 52 μC/cm² at 25 ℃ (1Hz). In addition, ceramics with x = 0.4 showed a relatively large electric-field-induced strain (S_max/E_max = 250 pm/V) at a high temperature of 200 ℃. Transmission electron microscopy for x = 0.4 provides evidence of polar nanosized domains with R3c rhombohedral structure. It is suggested that the presence of the nanosized domains is the origin of relaxor-like dielectric behavior.