Domain structure in the monoclinic Pm phase of Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals

The domain structure of (1-x)Pb(Mg1/3Nb2/3)O-3-xPbTiO(3) single crystals with composition xapproximate to0.33 in the range of the morphotropic phase boundary (MPB) was studied. Based on the analysis of spontaneous strain compatibility and charge of domain walls, we have established the permissible domain arrangements for the ferroelectric phases of different symmetries, which are expected to occur in the range of the MPB. Examination of (001)-oriented unpoled and electrically poled (along the [001] direction) crystal plates in a polarizing microscope reveals a monophase state with the domain structure compatible with the structure theoretically predicted for the M-C monoclinic phase (space group Pm), which was recently discovered in the compositions close to the MPB by x-ray and neutron diffraction studies. In the unpoled crystal, the 180degrees walls between the domains whose spontaneous polarization vectors are parallel to the plane of the crystal plate (i.e., a-domains) are observed. The domain structure of the poled crystal is predominantly composed of crystallographically prominent W-f walls parallel to (001) (i.e., the plane of the crystal plate) and inclined S walls parallel to [110] or [1 (1) over bar0] direction. In poled and unpoled samples, an optical rotatory polarization effect is found, which is related to the inhomogeneity of the sample resulting from the mixture of domains. (C) 2004 American Institute of Physics.