Domain configuration and crystal structure of Pb(Zn1/3Nb2/ 3)O-3-5%PbTiO3 crystals as a function of the electric-field direction

The domain configuration of 0.95Pb(Zn1/3Nb2/3)O-3-0.05PbTiO(3) single crystals was investigated as a function of the applied electric-field direction with respect to the crystallographic orientation. A normal ferroelectric domain structure, which was not observable in virgin crystals (not exposed to electric field), appeared upon the electric-field (E-field) induced transition from the relaxor state to the normal ferroelectric state. After E-field was applied along the polar <111> direction and removed, a band-shaped domain configuration appeared as a result of subsequent depolarization. The depoled <111> crystal consisted of predominantly (110) domain boundaries, which represents the minimum energy domain state in rhombohedral ferroelectrics. In contrast, crystals must transform into the phase with the symmetry lower than rhombohedral, i.e., monoclinic structure, by an E-field application along <001>. Domain boundaries in <001> poled crystals were indexed to be (001), being a favorable state for monoclinic ferroelectrics. The dependence of the domain configuration upon the E-field application direction could be explained using the relationship between the mechanical compatibility with respect to the ferroelectric strain and the crystal symmetry of a domain. The residual strain on domain boundaries in <001> crystals may inhibit crystals to recover the rhombohedral structure, resulting in a monoclinic ferroelectric crystal even upon the removal of the E-field.