Electric field dependence of piezoelectric properties for rhombohedral 0.955Pb(Zn_1/3Nb_2/3)O₃- 0.045PbTiO₃ single crystals

The electric field dependence of the piezoelectric properties of rhombohedral 0.955Pb(Zn_1/3Nb_2/3)O₃-0.045PbTiO₃ crystals were investigated as a function of orientation with respect to the prototypic (cubic) axes. For 〈111〉 oriented fields, depolarization and subsequent domain reorientation resulted in an apparent maximum in the piezoelectric coefficients occurring at ∼5 kV/cm, followed by nonhysteretic d_ij saturation, indicating a single domain state under bias. By extrapolation, single domain values for the piezoelectric coefficients d₃₃ and d₃₁ were determined to be 125 and -35 pC/N, respectively. The hydrostatic piezoelectric coefficient d_h for single domain crystals was calculated to be ∼55 pC/N, coincident with the experimentally determined values under hydrostatic pressure. For 〈001〉 oriented fields, piezoelectric coefficients d_33〈001〉 and d_31〈001〉 as high as 2250 and -1000 pC/N were determined, respectively. Although a high value of d_h〈001〉 (∼250 pC/N) was expected, the experimentally determined value was only ∼50 pC/N. A change of polar vector within the crystal lattice was discussed in relation to the volume strain associated with an E-field induced phase transition and the possible origin of the discrepancy in hydrostatic d_h values.