Electric-field-induced phase transitions of 〈001〉-oriented Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ single crystals

Electric-field-induced phase transitions and piezoelectric properties of 〈001〉-oriented Pb(Mg_1/3Nb_2/3)O ₃-32%PbTiO₃ (PMN-PT) single crystals have been investigated as a function of temperature. It was found that the phase transitions and piezoelectric properties for PMN-PT crystals are strongly dependent on temperature. The measurements of polarization and longitudinal strain as a function of a unipolar electric field show that the field for the induced monoclinic-tetragonal phase transition decreases linearly with temperature in the range between 23°C and 75°C. Raising the temperature can stabilize the tetragonal phase in 〈001〉-oriented PMN-PT crystals. The effective longitudinal piezoelectric constant, d₃₃, in the monoclinic phase increases with temperature. Meanwhile in the field-induced tetragonal phase, d₃₃ is much smaller and has little change with temperature. The electric-field-induced phase transition from a cubic phase to a tetragonal phase was observed at 125°C.