Stress and temperature-induced phase transitions and thermal expansion in (001)-cut PMN-31PT single crystal

• The stress-induced MA → R transition is proposed.
• The stress enhances the temperature stability of R phase.
• The stress induces a large thermal contraction coefficient α = −17 × 10−6 K−1.

Phase transitions and thermal-expansion behavior were investigated in (001)-cut 0.69Pb(Mg1/3Nb2/3)O3−0.31PbTiO3 (PMN-31PT) single crystals under different stress and temperature conditions. At room temperature, moderate stress is found to induce monoclinic (MA) → rhombohedral (R) transition, whereas high stress promotes rhombohedral (R) → orthorhombic (O) transition. The transition behavior of the sample during heating is considerably more complex than during cooling. These transitions are associated with a change in local symmetry based on a model of stress-induced polarization rotation. Thermal expansion behavior of the sample strongly depends on stress. Under 14 MPa, the sample displays linear-contraction behavior, and a large contraction coefficient α = −17 × 10−6 K−1 is obtained within a wide temperature range (from room temperature to 110 °C).