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 d33[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.
Crystal orientation dependence of piezoelectric properties has been calculated phenomenologically for lead zirconate titanate (PZT) in the three-dimensional space. The calculation has been made for tetragonal PZT 40/60 (40% PZ and 60% PT) and rhombohedral PZT 60/40 compositions. The maximum longitudinal piezoelectric constant d
33 and electromechanical coupling factor k
33 in the rhombohedral composition were found to be at 57° and 51° angles, respectively, canted from the spontaneous polarization direction. This suggests that thin film piezoelectric actuators or sensors should employ a rhombohedral composition with the perovskite [100] epitaxially-oriented configuration.
Domain switching has been observed in 0. 9PZN -0. 1PT single crystals under the influence of electric field. The crystal being near the morphotropic phase boundary contains two phases -rhombohedra1 and tetragonbal. The electric field was applied along two principal directions [OOl] and [lli]. Their formation as the temperature is reduced with the electric field is discussed here. For electric field along [OOl]. it was found that a single domain could be induced in tetragonal phase. When the electric field was applied along [lll], the formation of domains as temperature is reduced are shown to be remarkably similar to those formed when the temperature is fixed and the concentration of IT varied. This type of domain hierarchy may be a contributing factor for the high k (electromechanical factor) observed in these crystals.
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