Ultra-high energy harvester performance in KNN-based textured piezoceramics via multiscale reconfiguration design

The lower electromechanical performance of lead-free piezoelectric materials remains a critical bottleneck impeding their ability to replace lead-based materials in energy harvesting. To overcome this predicament, here, we propose a multiscale reconfiguration design to tailor the intricate coupling between the structure and properties of (K,Na)NbO₃-based piezoelectric materials. The multiphase coexistence, local structural heterogeneity, enhanced crystal anisotropy, and acceptor doping yielded (K,Na)NbO₃-based ceramics with a harmonious balance between the piezoelectric coefficient and the dielectric constant. As a result, the (K,Na)NbO₃-based textured ceramics demonstrate exceptional piezoelectric properties, including a piezoelectric charge coefficient (d₃₃) of 551 pC·N⁻¹ and a piezoelectric voltage coefficient (g₃₃) of 54.2 mV·m·N⁻¹. The energy harvesting devices exhibit an ultrahigh instantaneous output power (P_out) of 4.85 mW and an instantaneous output power density (P_D) of 70.2 μW·mm⁻³. This work provides valuable insights into the design and development of high-performance lead-free piezoelectric ceramics and significantly advances the potential of (K,Na)NbO₃-based ceramics as viable replacements for Pb(Zr,Ti)O₃-based ceramics in energy harvesting applications.