OPTICAL OBSERVATION OF HETEROPHASE AND DOMAIN-STRUCTURES IN RELAXOR FERROELECTRICS PB(ZN1 3NB2/3)O-3/9-PERCENT-PBTIO3/

Phase boundary and domain structure in relaxer ferroelectrics Pb(Zn1/3 Nb2/3)O-3/9%PbTiO3 were observed using a (111) plate under a polarizat ion microscope. The dielectric constant was measured simultaneously to determine exact transition temperatures and to connect the dielectric behavior with phase boundary movements. Movement of the phase boundar y between cubic and tetragonal phases was observed at the temperature T-c where the dielectric constant changed abruptly. Below T-c, tetrago nal and rhombohedral phases coexisted over a wide temperature range. T he complicated domain/phase patterns are classified into two blocks ac cording to extinction position. The difference in extinction positions between the two blocks deviated from 30 degrees and manifested temper ature dependence. This fact indicates that the symmetry-lowering occur s in the heterophase. A small, but the distinct temperature hysteresis of the dielectric constant was related to the nucleation and growth o f one phase into another phase.