Transverse-mode properties of [011]-poled Pb(Zn_1/3Nb _2/3)O₃-PbTiO₃ single crystals: effects of composition, length orientation, and poling conditions

The poling responses of [011]-poled Pb(Zn_1/3Nb _2/3)O₃-PbTiO₃ [PZN-PT] single crystals of a range of compositions and two length orientations have been investigated. The results show that [011]-poled PZN-PT single crystals of [100]-length-cut exhibit much superior transverse properties than [011̄]-length-cut crystals. Extremely high d₃₁ values of -(3000-4000) pC/N and k₃₁ ∼ 0.90-0.96 were obtained for PZN-7%PT optimally [011]-poled crystals. This composition, however, shows degraded dielectric and piezoelectric properties when poled at ≥0.6kV/mm. In contrast, PZN-4.5%PT and PZN-6%PT single crystals show no signs of overpoling even when poled up to 2.0kV/mm, exhibiting d ₃₁ ≈ -(2700-3200) pC/N and k₃₁ ∼ 0.90-0.92 (for PZN-6%PT) and d₃₁ ≈- 1500 pC/N and k₃₁ ∼ 0.86-0.90 (for PZN-4.5%PT), respectively. The presence of certain amounts (i.e., 10-15%) of orthorhombic phase in a rhombohedral matrix has been found to be responsible for the superior transverse piezoelectric properties of optimally [011]-poled PZN-(6-7)%PT.