Crystal orientation dependence of piezoelectric properties of lead zirconate titanate near the morphotropic phase boundary

The piezoelectric and dielectric constants in different crystal orientations of the lead zirconate titanate (PZT) have been phenomenologically calculated for the compositions near the morphotropic phase boundary at room temperature. For a tetragonal PZT, the effective piezoelectric constant d₃₃ monotonously decreases as the crystal cutting angle from the spontaneous polarization direction [001] increases. However, for a rhombohedral PZT, the effective piezoelectric constant d_33[001]// along the perovskite [001] direction was found to be much larger than those along the spontaneous polarization direction [111]. This crystal orientation-related enhancement is emphasized as the composition approaches the morphotropic phase boundary. This suggests that by adopting the perovskite [001] orientation with a rhombohedral composition near the morphotropic phase boundary, the piezoelectric constant d₃₃ for PZT can be greatly enhanced.