Relaxor ferroelectric materials, such as Pb[(Mg0.33Nb0.67)1-xTix]O3 (PMN-PT) with generic stoichiometry, undergo a ferroelectric-to-paraelectric phase transition as a function of temperature. The exact transition characterized by Curie temperature (Tc) varies as a function of chemistry (x), i.e., the concentration of Ti. In this study, we investigated the structural phase transition by exploring the temperature dependence of the single-crystal elastic properties of Pb[(Mg0.33Nb0.67)0.7Ti0.3]O3, i.e., x≈0.3. We used resonant ultrasound spectroscopy to determine the elasticity at elevated temperatures, from which Tc=398±5K for PMN-PT (x≈0.3) was determined. We report the full elastic constant tensor (Cij={C11,C12,C44}), acoustic attenuation (Q-1), longitudinal (VP) and shear (VS) sound velocities, and elastic anisotropy of PMN-PT as a function of temperature for 400Tc the material first stiffens and reaches maxima in the vicinity of the Burns temperature (Tb∼673K), followed by a more typical gradual softening of the elastic constants. Similar temperature-dependent anomalies are also observed with anisotropy and Q-1, with minima in the vicinity of Tb. We used the temperature dependence of Cij, Q-1, VP,VS, and anisotropy to infer the evolution of polar nanoregions as the material evolved from T>Tc.

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Physical Review B