Birefringence imaging measurements on the phase diagram of Pb(Mg1/3Nb2/3)O3-PbTiO3

The phase diagram of (PbMg1/3Nb2/3O3)(1-x)-(PbTiO3)(x) (PMN-PT) has been determined to, high accuracy over, the whole compositional range using birefringence imaging. A steep change has been detected in the thermal hysteresis of phase transitions in the morphotropic phase boundary region at x = 0.295 at the boundary between relaxor and non-relaxor phases. At the same composition at a temperature about 30 degrees C below T-c a monoclinic phase appears. The phase transition between non-relaxor and the monoclinic phase is characterized by a pronounced thermal hysteresis, and a large jump in birefringence, showing that this is of first order: A significant change in slope for the compositional dependence-of Tc has-been: found for x similar or equal to 0.45, suggesting a boundary between the tetragonal phase and a phase of lower symmetry. The temperature dependence of the birefringence has been, measured for a number of different compositions in the range 0.3 < x < 1, in which it is found that the birefringence of the monoclinic phase is much higher than that seen in the other phases for x < 0.5.