Intermediate structural phases in rare-earth substituted BiFeO3

Abstract The room-temperature crystal structure and local ferroelectric properties of Bi 0.85 RE 0.15 FeO 3 (RE = Sm, Gd, Dy) polycrystalline samples have been investigated by X-ray diffraction (XRD) and piezoresponse force microscopy (PFM) techniques. XRD measurements show that the rare-earth substitution causes the transformation of R3c structure typical of BiFeO 3 to yield orthorhombic phases with √2 a × 2√2 a × 2 a and √2 a × 2 a × √2 a superlattices ( a is the parameter of the cubic perovskite subcell). Results of PFM investigations imply that both the orthorhombic phases are polar. The models describing crystal structure of the phases are discussed.