Coexistence of MA and MC phases in Pb(Mg1/3Nb2/3)0.68Ti0.32O3 single crystals

The coexistence of M-A (space group C-m) and M-C (space group P-m) phases in as-grown Pb(Mg1/3Nb2/3)(0.68)Ti0.32O3 (PMNT32) single crystals is observed at room temperature under polarization microscopy. Laminar M-A and M-C domains normal to < 110 >(cub) direction appear alternately in PMNT32 single crystals. In the heating run, the M-A domains show a phase transition sequence of M-A-M-C-cubic, while the M-C domains show only a phase transition of M-C to cubic. In the cooling run, the phase transition sequence of cubic-M-C-M-A can be observed in the whole sample. It is suggested that the internal stress in the as-grown PMNT crystals is the main reason for the coexistence of the M-A and M-C phases.