Overpoling-induced property degradation in Pb(Mg1∕3Nb2∕3)O3–PbTiO3 single crystals of near-morphotropic phase boundary compositions

Overpoling phenomenon has been observed in flux-grown Pb(Mg1∕3Nb2∕3)O3–(31–32)%PbTiO3 single crystals when poled above 0.4kV∕mm at room temperature. This leads to increased property variations at intermediate poling fields (0.6–0.8kV∕mm) and to the degradation of piezoelectric properties at high poling fields (⩾1.0kV∕mm). In comparison, both PMN–28%PT and PMN–30%PT crystal compositions are resistant to overpoling, of which PMN–30%PT exhibits superior dielectric and piezoelectric properties with KT≈7500–9000, d33≈2200–2500pC∕N, and d31≈1100–1400pC∕N. The electromechanical coupling factors (k33=0.90–0.94; k31=0.48–0.55, and kt=0.58–0.62) are relatively insensitive to the poling field and crystal composition.