Hydrostatic piezoelectric properties of [011] poled Pb(Mg _1/3Nb_2/3)O₃-PbTiO₃ single crystals and 2-2 lamellar composites

The hydrostatic piezoelectric properties of [011] poled Pb(Mg _1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) crystals and corresponding 2-2 crystal/epoxy composites were investigated. The crystal volume ratio and compositional dependencies of the hydrostatic charge and voltage coefficients (d_h and g_h) and hydrostatic figure of merit (FOM) d_h × g_h were determined, where large FOM value of 3.2 pm²/N with high stability as a function of hydrostatic pressure was achieved for rhombohedral crystal composites. In addition, the stress amplification effects of the face-plate and different epoxy matrixes were investigated, with maximum FOM value being on the order of 92 pm²/N, indicating that 2-2 crystal/epoxy composites are promising materials for hydrostatic applications.