Single crystals of 67Pb(Mg1/3Nb2/3)O3–33PbTiO3 (PMN-PT, PMNT) relaxor-based complex perovskite solid solution grown by Bridgman method have pseudo-cubic symmetry under ambient conditions. Examination by means of polarized light microscopy showed that the microstructure of the crystals was dominated by a large number of coarse twin domains. It was confirmed that the most common composition planes were {110} in addition, {112} planes were also observed. These twins may be associated with the transformation of PMNT complex perovskite from the cubic to tetragonal upon a decrease in temperatures. The morphology of the domain structure may be explained from the theory of martensitic transformation.

The 90° macrodomains in tetragonal Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMNT) crystals take the shape of coarse and straight strips under optical microscopes and scanning electron acoustic microscopes. However, 71° or 109° domains in rhombohedral PMNT crystals are relatively poor in contrast and become clearer, coarser and straighter as their composition becomes closer to morphotropic phase boundaries, showing an evolution series of micro-to-macro domain transformation. Moreover, domain configurations are also dependent on the nucleation and growth rate of domains, the crystal defects, and the cooling rate through Curie temperature. The appearance of macrodomains arises from the strengthening of depolarization field and the weakening of random field.