Polarization Rotation via a Monoclinic Phase in the Piezoelectric 92% PbZn1/3Nb2/3O3-8% PbTiO3

The origin of ultrahigh piezoelectricity in the relaxor ferroelectric PbZn_1/3Nb_2/3O₃-PbTiO₃ was studied with an electric field applied along the [001] direction. The zero-field rhombohedral R phase starts to follow the direct polarization path to tetragonal symmetry via an intermediate monoclinic M phase, but then jumps irreversibly to an alternate path involving a different type of monoclinic distortion. Details of the structure and domain configuration of this novel phase are described. This result suggests that there is a nearby R-M phase boundary as found in the Pb\(Ti,Zr\)O₃ system.