Large piezoelectric response of BiFeO3/BaTiO3 polycrystalline films induced by the low-symmetry phase

Abstract

BaTiO₃, BiFeO₃ and BiFeO₃/BaTiO₃ polycrystalline films were prepared by the radio frequency magnetron sputtering on the Pt/Ti/SiO₂/Si substrate. The phase structure, converse piezoelectric coefficient and domain structure of BaTiO₃, BiFeO₃ and BiFeO₃/BaTiO₃ thin films are characterized by XRD and PFM, respectively. The converse piezoelectric coefficient d₃₃ of BiFeO₃/BaTiO₃ thin films is 119.5 pm V⁻¹, which is comparable to that of lead-based piezoelectric films. The large piezoelectric response of BiFeO₃/BaTiO₃ thin films is ascribed to the low-symmetry T-like phase BiFeO₃, because the spontaneous polarization vector of T-like phase (with monoclinic symmetry) BiFeO₃ can rotate easily under external field. In addition, the reduced leakage current and major domains with upward polarization are also attributed to the large piezoelectricity.