Orientation dependence of the intrinsic converse longitudinal piezoelectric constant for 0.67Pb(Mg_1/3Nb_2/3)O₃–0.33PbTiO₃ ferroelectric films with a rhombohedral structure

The general orientation dependence of the intrinsic converse longitudinal piezoelectric constant d(nn)(f) in an epitaxial rhombohedral film is calculated by taking into account the effect of substrate clamping. Theoretical predictions are made for d(nn)(f) of epitaxial 0.67Pb(Mg1/3Nb2/3)O-3-0.33PbTiO(3) rhombohedral films, which are compared with experimental results on pseudo-cubic (001), (110) and (111) orientations.