Polarisation Orientation Effects and Hydrostatic Parameters in Novel 2–2 Composites Basedon PMN–xPT Single Crystals

Abstract

Polarisation orientation effects in piezo-active composites based on relaxor-ferroelectric single crystals of (1–x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 open up new possibilities to vary the effective electromechanical properties and related parameters. In the present paper the hydrostatic performance of 2–2 parallel-connected single crystal / auxetic polymer composites is studied for x = 0.28 – 0.33 and two poling directions of the single-crystal component, [001] (4mm symmetry) and [011] (mm2 symmetry) in the perovskite unit cell. The effect of the orientation of the main crystallographic axes in the single-crystal component on the hydrostatic piezoelectric coefficients d*h, eh* and squared figure of merit d*hgh* is analysed for three rotation modes in single crystals and at various anisotropy of their piezoelectric and elastic properties. The role of the auxetic polymer component is emphasised in the context of the large hydrostatic parameters and anisotropy of squared figures of merit d*3jg3j* (j = 1, 2 and 3). The largest maximum values of d*h and e*h (1990 pC/N and 42.5 C/m2, respectively) are achieved in the composite based on [011]-poled 0.71Pb(Mg1/3Nb2/3)O3–0.29PbTiO3.