Domain orientations and piezoelectric properties in novel 2–2-type composites with two single-crystal components

The present paper is concerned with the piezoelectric properties and related parameters of the 2–2-type parallel-connected composites wherein rotations of the main crystallographic axes in ferroelectric single crystal components are analyzed. The composite consists of layers of two types that are regularly arranged along the non-polar axis. The Type I layer is a single domain 0.63Pb(Mg1/3Nb2/3)O3–0.37PbTiO3 single crystal (either tetragonal in Composite I or orthorhombic in Composite II). The Type II layer is a Li2B4O7 single crystal/polyethylene medium with 0–3 connectivity. The composite as a whole is characterized by 2–0–2 connectivity. The following parameters of the composite are studied by taking into account the polarization orientation effect in the Type I layer and the microgeometry of the composite in the Type II layer: piezoelectric coefficients d3j* and g3j*, their hydrostatic analogs dh* and gh*; hydrostatic squared figure of merit dh* gh*; piezoelectric anisotropy factors d33*/d32* and d33*/d32*. It is shown that large values of the studied piezoelectric coefficients, hydrostatic parameters and anisotropy factors make Composite II more preferable in comparison to Composite I for hydroacoustic, piezoelectric sensor and energy-harvesting applications.