Enhanced transverse piezoelectric properties by composition and poling electric field induced phase transition in PIN–PMN–PT single crystal near morphotropic phase boundary

A monoclinic phase is the bridge between the rhombohedral and tetragonal phases in the Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT) single crystal near the morphotropic phase boundary (MPB), which is related to the superior piezoelectric performance. In this paper, the different phase transition process in the unpoled PIN–PMN–PT single crystals near MPB induced by composition variation was presented first. Based on this, direct current poling (DCP) and alternating current treatment (ACT) were applied on these samples. Also, the crystals by DCP–ACT have shown a more complex ferroelectric phase transition process than that by DCP, which is related to the induced monoclinic phase by applying an AC electric field. The transverse piezoelectric properties of the PIN–PMN–PT single crystal with various compositions by DCP and DCP–ACT were compared. ACT enhanced the electromechanical coupling coefficient k31, elastic compliance constant S11E, and dielectric permittivity e33T/e0 of the pre-DCP PIN–PMN–PT single crystals in the macrorhombohedral phase. As a result, the transverse piezoelectric constant d31 of the crystals with various compositions was enhanced to be −1240, −1663, and −1252 pC/N by DCP–ACT, which were 61.7%, 73.0%, and 60.8% higher than that by DCP. However, ACT has little effect on the pre-DCP PIN–PMN–PT crystal with macrocoexistence of rhombohedral and monoclinic phases. The AC electric field could be a useful way for tuning the coexistence of rhombohedral and monoclinic phases in the PIN–PMN–PT crystal near MPB to achieve high transverse piezoelectric performance.