Poling-free relaxor-PbTiO3 single crystals

Relaxor-PbTiO₃ ferroelectric single crystals have drawn attention aiming at high-end piezoelectric applications thanks to their excellent piezoelectric properties. Like all the other ferroelectrics, relaxor-PbTiO₃ single crystals can only be piezoelectrically active upon being electrically poled. However, this poled state is thermally unstable, limiting their uses because of their relatively low depolarization temperature. Here, we show that a non-destructible permanent poled state can be realized in relaxor-PbTiO₃ single crystals by forming a 0–3 composite in the presence of charged mobile point defects. We demonstrate this on solid-state grown 0.71 Pb(Mg_1/3Nb_2/3)O₃-0.29PbTiO₃ single crystals doped with Mn (Mn-PMNT) as a donor with well-aligned and dispersed boron-rich MgO-based inclusions (MBIs). Mn-PMNT_MBI sharing [001] axis with arrayed MBIs were spontaneously polarized during cooling across the Curie temperature without an external electric field. The piezoelectric coefficient and dielectric permittivity of self-poled Mn-PMNT_MBI crystals were as large as 90% of that achieved by a direct-current poling treatment at room temperature, and such poled state was reproducible against repeated thermal cycles. We expect that the poling-free high-performance piezoelectric relaxor-PbTiO₃ single crystals offer an avenue for piezoelectric-based devices by removing the working temperature limit as one of the inherent fundamental limitations.