Longitudinal piezoelectric effect and hydrostatic response in novel laminar composites based on ferroelectric ceramics

Abstract

Effective piezoelectric coefficients d33*, g33*, their hydrostatic analogs dh*, gh*, and related squared figures of merit d33*g33* and dh*gh* are studied by taking into account porosity of both the ceramic and polymer layers in novel 2–2-type parallel-connected composites. In two related composites based on the PZT-type ferroelectric ceramic, the polymer layers have different compositions and volume fractions of air pores. The influence of pore shape, volume fractions of pores in the adjacent layers and elastic properties of the polymer component on the piezoelectric sensitivity and related parameters of the manufactured composites is first studied. Experimental volume-fraction dependences of the aforementioned parameters of the composites are analysed in terms of a 2–0–2–0 composite model where different porosity levels in the ceramic and polymer layers are considered. A mutual influence of porosity in the ceramic and polymer layers leads to large values of dh*/ d33*≈ 0.80–0.93, and this has no analogs among the piezo-active composites. Due to large values of d33*~102 pC/N, g33*~102 mVm/N, dh*≈ 300–500 pC/N, d33*g33*≈ (60–70).10−12 Pa−1, and dh*gh*≈ (40–60).10−12 Pa−1, the studied composites are important for piezoelectric sensor and hydroacoustic applications.