Advanced Piezo-Active 2–1–2 Composites with Large Parameters for Hydroacoustic and Energy-Harvesting Applications

Novel piezo-active 2–1–2 composites with two single-crystal components are studied to show their large hydrostatic parameters and figures of merit concerned with the hydrostatic, longitudinal, and transverse piezoelectric effects. The 2–1–2 composite contains layers of domain-engineered [0 1 1]-poled relaxor-ferroelectric (1 – x)Pb(Zn1/3Nb2/3)O3 – xPbTiO3 single crystal (x = 0.0475–0.09) and layers that contain aligned piezoelectric Li2B4O7 single crystal rods in polyethylene, and these layers are distributed regularly and in the form of an elliptic cylinder. Due to the microgeometry of the composite and the piezoelectric properties of the single-crystal components, large values of the hydrostatic figure of merit \(d_{h}^{*} g_{h}^{*} > 2 \cdot 10^{ - 10} \;{\text{Pa}}^{ - 1}\) and longitudinal figure of merit \(d_{33}^{*} g_{33}^{*} \sim 10^{ - 10} \;{\text{Pa}}^{ - 1}\) are achieved in specific volume-fraction and aspect-ratio range, at relatively small volume fractions of the single-crystal rods. An effect of the aspect ratio of the rod base on the piezoelectric performance and figures of merit if the composite is discussed. Large figures of merit of the studied composites can promote hydroacoustic and piezoelectric energy-harvesting applications of the studied 2–1–2 composites.