2013 年 55 巻 5 号 p. 278-284
Polarization rotation is the key for interpretation of the piezoelectricity in Pb（Ti1-xZrx）O3（PZT）and other piezoelectric ceramics. We found the monoclinic phase in BiCo1-xFexO3（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 BiCo1-xFexO3 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.