Simultaneous achieving giant piezoelectric charge and voltage coefficients in holmium-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals

Abstract

The piezoelectric charge coefficient (d₃₃) and piezoelectric voltage coefficient (g₃₃) are critical parameters for piezoelectric materials, with their product, d₃₃ × g₃₃, serving as the figure of merit (FOM) for piezoelectric energy harvesters. While large d₃₃ and g₃₃ values are typically achieved individually in piezoelectric materials, obtaining both simultaneously remains a significant challenge. By leveraging the ABO₃ perovskite structure of relaxor ferroelectric single crystals, an unprecedentedly ultrahigh d₃₃ × g₃₃ value has been realized in holmium-doped Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) single crystals. This system reports average values of d₃₃, g₃₃ and d₃₃ × g₃₃ of 4400 pC N⁻¹, 45.2 × 10⁻³ Vm N⁻¹ and 199 pm² N⁻¹, respectively. Notably, the d₃₃ × g₃₃ value surpasses that of other Pb-based relaxor ferroelectric crystals. Atomic-scale analysis attributes the giant piezoelectric properties to the introduction of holmium ions, which disrupt long-range ferroelectric ordering, forming slush-like multipolar states with the relatively large nano-tetragonal phase in the local structure. This promotes polarization rotation and lattice distortion, enhancing piezoelectric performance. Thus, this study provides valuable insights into the mechanisms behind high piezoelectric properties, positioning this advanced crystal for potential applications in piezoelectric sensors, energy harvesters, and related technologies.