Polarization Rotation in BiCo_1-xFe_xO₃

Abstract

Polarization rotation is the key for interpretation of the piezoelectricity in Pb（Ti_1-xZr_x）O₃（PZT）and other piezoelectric ceramics. We found the monoclinic phase in BiCo_1-xFe_xO₃（x～0.7）that is isostructural with the low temperature phase of PZT at the morphotropic phase boundary（MPB）. Precise structural analysis by electron diffraction and powder synchrotron X-ray diffraction revealed that the monoclinic perovskite BiCo_1-xFe_xO₃ exhibits Cm symmetry and showed polarization rotation as functions of composition and temperature. The second order structural transition from tetragonal to monoclinic structures was accompanied by a rotation of the polarization vector from the［001］to［111］directions of a pseudo cubic cell.