PHASE TRANSITION IN Pb(Mg_1/3Nb_2/3)_0.68TiO_0.32O₃ SINGLE CRYSTAL

ABSTRACT

Phase transition of (001)-cut Pb(Mg_1/3Nb_2/3)_0.68Ti_0.32O₃(PMNT32%) single crystal have been investigated by polarizing light microscopy in the temperature ranged form room temperature to 200 K. The transformation from monoclinic (M_A) to cubic (C) phase through an intermedial monoclinic (M_C) phase, i.e. M_A-M_C-C, was observed in the heating run, and the C-M_C-M_A phase transition sequence was observed in the cooling run. The temperature-induced rotation of extinction position, which was the result of polarization rotation, was observed in M_C phase. It is interesting that tetragonal (T) phase has not been reached before the M_C phase turn into cubic phase. The existing phase diagram for PMNT system was improved by this experimental result. In addition, it was found the phase transition processes of M_C-M_A and cubic-M_C show distinct characters though both of they are first-order.

Keywords:

PACS:

• 77.80.Bh
• 77.80.Dj
• 77.84.Dy

Acknowledgments

Current address: Department of Engineering, University of Cambridge, Cambridge, CB2 1PZ, UK