Ultrahigh energy harvesting performance in lead-free piezocomposites with intragranular structure

Abstract

Piezoelectric energy harvesting is a promising means to realize self-powered microelectronic devices. However, the low power density severely restricts its development. The key challenge lies in manipulating ferroic domain structure in order to overcome thermodynamic constraints (high piezoelectric constant d together with high dielectric constant ε) of piezoelectric materials, and obtain a high figure of merit for energy harvesting (transduction coefficient = d2/ε). Here, we propose a new strategy to decouple between ε and d, and thus enhance the salient figure of merit for polycrystalline ceramics by manipulating the intragranular structure. We fabricated high-quality ferroelectric/metal (Ba0.85Ca0.15Ti0.9Zr0.1O3/Ag, BCTZ/Ag) lead-free piezocomposites with intragranular structure, in which the electrostrictive coefficient (Q) is substantially enhanced, leading to stable piezoelectric coefficient. Meanwhile, the non-ferroelectric metal Ag phase distributed in BCTZ ferroelectric grains results in the sharp drop of dielectric constant. The transduction coefficient, current density and power density of BCTZ/0.03Ag sample are up to 10000 × 10−15 m2/N, 1.04 μA/mm2 and 3.62 μW/mm3, outperforming state-of-the-art lead-free piezoelectric ceramics. This work provides a new paradigm for the design of high-performance lead-free piezoelectric energy harvesting materials.