Excellent power generation and enhanced mechanical properties in PPT-structured Pb-free piezoceramics with ZrO2 inclusions

Abstract

Piezoelectric energy harvesters (PEHs) are important for wireless sensors to achieve self-powering, for which the piezoceramics must not only have a large figure of merit (FOM = d²/ε) to produce high energy density but also strong mechanical properties to prevent fatigue failure. To address the above-mentioned points, a lead-free composite ZrO₂/(1 − x)(K_0.48Na_0.52)(Nb_0.96Sb_0.04)O₃–x(Bi_0.5Na_0.5)ZrO₃ (ZrO₂/(1 − x)KNNS–xBNZ) was designed. The optimal x = 0.04 sample exhibited enhanced fracture toughness (K_IC = 1.36 MPa m^1/2) and an elevated figure of merit (FOM = 4827 × 10⁻¹⁵ m² N⁻¹) owing to the toughening of the ZrO₂/perovskite composite and the formation of polymorphic phase transition (PPT) with a hierarchical domain configuration. The cantilever beam-type PEH made using the x = 0.04 ceramic showed a high-power density of 380 μW cm⁻³ together with excellent fatigue resistance and is suitable to be used as an environment-friendly PEH instead of batteries to realize self-energy supply in wireless sensors.