In Situ Di‑, Piezo‑, Ferroelectric Properties and Domain Configurations of Pb(Sc<sub>1/2</sub>Nb<sub>1/2</sub>)O<sub>3</sub>–Pb(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)O<sub>3</sub>–PbTiO<sub>3</sub> Ferroelectric Crystals

Relaxor ferroelectric crystals, such as Pb­(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)­O<sub>3</sub>–PbTiO<sub>3</sub> and Pb­(Zn<sub>1/3</sub>Nb<sub>2/3</sub>)­O<sub>3</sub>–PbTiO<sub>3</sub>, exhibit high piezoelectric properties. However, they cannot meet the need of high power transducers, due to their low phase transition temperatures and low coercive fields. Thus, it is urgent to develop new-type ferroelectric crystals. Here, a ternary solid solution of Pb­(Sc<sub>1/2</sub>Nb<sub>1/2</sub>)­O<sub>3</sub>–Pb­(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)­O<sub>3</sub>–PbTiO<sub>3</sub> is a good candidate. By the regulation of growth techniques and the control of raw compositions, Pb­(Sc<sub>1/2</sub>Nb<sub>1/2</sub>)­O<sub>3</sub>–Pb­(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)­O<sub>3</sub>–PbTiO<sub>3</sub> crystals with different compositions are obtained, which present perovskite phases without any trace of impurity. In situ investigations of di-, piezo-, ferroelectric properties and the observation of domain configurations are realized in Pb­(Sc<sub>1/2</sub>Nb<sub>1/2</sub>)­O<sub>3</sub>–Pb­(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)­O<sub>3</sub>–PbTiO<sub>3</sub> crystals, which exhibit large di-, ferro-, piezoelectric responses, typical domain switching, high poled and thermal stabilities. At room temperature, the maximum piezoelectric constant is found to be 1550 pC/N, with the maximum peak to peak strain value of 0.57% and coercive field of 4–6 kV/cm. The speckle-shaped nanodomains and butterfly hysteresis loops represented by the variation of amplitudes further indicate large piezoelectric responses of PSN–PMN–PT crystals. Furthermore, the rhombohedral–tetragonal phase transition temperature is more than 120 °C, indicating good thermal stabilities with stable ferroelectricity and large piezoelectric response in a wide temperature range.