Dielectric and direct temperature changes induced by an electric field were investigated in a $⟨011⟩$-oriented $0.72\text{Pb}\left({\text{Mg}}_{1/3}{\text{Nb}}_{2/3}\right){\text{O}}_3\text{−}0.28{\text{PbTiO}}_3$ single crystal as a function of temperature. Field-induced temperature changes were measured directly from the surface of the crystal by a thermocouple. Three distinct anomalies at temperatures of $\sim 68$, $\sim 96$, and $\sim 128°\text{C}$ were identified in the dielectric and temperature change responses of the crystal, dividing the temperature range into four distinct phase stability regions with different field-induced behaviors. Just above the depolarization temperature of $128°\text{C}$, dielectric hysteresis showed a double-loop nature caused by a reversible nonpolar-polar phase transition accompanied by an increase in the electrocaloric temperature change. Two other reversible field-induced phase transitions with different field-induced thermal behaviors were evidenced in the polarization and temperature responses in the temperature ranges of $96–128°\text{C}$ and below $68°\text{C}$.

• Received 4 August 2010

DOI:https://doi.org/10.1103/PhysRevB.82.134119