Advanced composites based on relaxor-ferroelectric single crystals: From electromechanical coupling to energy-harvesting applications

Domain-engineered relaxor-ferroelectric single crystals with compositions near the morphotropic phase boundary are considered as a key component for modern high-performance piezo-active composites. The advantages of using the relaxor-ferroelectric single crystals of solid solutions of (1 - x)Pb(Mg1/3Nb2/3)O3 - xPbTiO3 and (1 - y)Pb(Zn1/3Nb2/3)O3 - yPbTiO3 in piezo-active composites of 2-2 and 1-3 configurations are discussed by taking into account the complex relationships between the outstanding properties of the components and the effective parameters of the composite structure as a whole. Examples of their high piezoelectric activity, strong electromechanical coupling, large piezoelectric anisotropy, and large hydrostatic parameters of the composites demonstrate how the relaxor-ferroelectric single-crystal component improves the effective parameters and promotes the formation of non-monotonic volume-fraction dependences of particular effective parameters that are of interest for a variety of piezotechnical applications, such as transducers, sensors, hydrophones, and energy-harvesting devices.