High-performance 1–3-type lead-free piezo-composites with auxetic polyethylene matrices

• We study piezoelectric sensitivity and hydrostatic response of lead-free composites.
• We examine the influence of the polymer Poisson’s ratio on the piezoelectric effect.
• The composites exhibit advantageous properties over lead-based piezo-materials.
• An infinitely large piezoelectric anisotropy in lead-free composites is achieved.

High piezoelectric sensitivity and large hydrostatic parameters are discussed for two 1–3-type single crystal/auxetic polymer composites. The single crystal components selected are based on lead-free (K,Na)(Nb,Ta)O3 and (Li,K,Na)(Nb,Ta)O3 solid solutions, and the auxetic polymers are characterised by Poisson’s ratios –0.83≤ ν   ≤–0.29. The composites examined exhibit advantageous properties over conventional lead-based piezo-active composites and ceramics such as high longitudinal piezoelectric coefficient g33⁎~(102–103) mV·m/N, squared figure of merit (Q33⁎)2~10–11 Pa−1, hydrostatic piezoelectric coefficient gh⁎~(102–103) mV·m/N and squared figure of merit (Qh⁎)2~(10–11–10−10) Pa−1. The composites also demonstrate an infinitely large anisotropy of piezoelectric coefficients d3j⁎.