Squared figures of merit and electromechanical coupling factors of a novel lead-free 1–3–0 composite for sensor and energy-harvesting applications

Piezoelectric sensitivity and energy-harvesting parameters are studied for a novel lead-free 1–3–0 composite where domain-engineered single-crystal rods are surrounded by a polymer matrix containing two types of air pores. Correlation between some effective parameters, concerned with the high piezoelectric sensitivity of the composite, and the elastic properties of its porous matrix is first stated. Diagrams are first built to show volume-fraction ranges wherein conditions for large squared figures of merit (Q33*)2=d33* g33*≥200⋅10−12 Pa−1 (longitudinal) and (Qh*)2=dh* gh*≥50⋅10−12 Pa−1 (hydrostatic) hold, where d33*, dh*. g33*, and gh* are piezoelectric coefficients of the composite. The studied composite is also of interest due to its large electromechanical coupling factors kt* ≈ 0.8–0.9 (thickness) and kh* ≈ 0.5–0.6 (hydrostatic). Piezoelectric sensitivity, electromechanical coupling factors and other characteristics are compared to those of a lead-containing 1–3–0 composite and a few 1–3 composites. Correlation between the effective parameters of the 1–3–0 composite and elastic properties of its porous matrix is discussed. Replacing the parallelepiped-shaped single-crystal rods with the cylindrical rods in the 1–3–0 composite leads to minor changes in the aforementioned parameters. The performance of the studied lead-free 1–3–0 composite proves its suitability for modern piezoelectric sensors, energy-harvesting and hydroacoustic devices.