Flexible lead-free piezo-/ferroelectric Bi_0.5(Na_0.6K_0.4)_0.5TiO₃ ceramic incorporated PDMS polymer composites for energy harvesting application

Environment friendly piezoelectric micro/nanogenerators have attracted tremendous attention due to the increasing demand of portable self-powered devices. Here, we report the synthesis of Bi_0.5(Na_0.6K_0.4)_0.5TiO₃ (BNKT) ceramic via solid state reaction method and the fabrication of BNKT:PDMS based flexible energy harvester. The synthesized BNKT ceramic exhibits well-defined fatigue free P-E hysteresis loops up to 10⁴ cycles favourable for high precision capacitors and sensors. A high value of piezoelectric charge coefficient (d₃₃ = 154 pC N⁻¹) was measured for BNKT ceramic, which indicates its potential application in flexible energy harvesting devices. A series of flexible BNKT:PDMS composite based microgenerators were fabricated with 10, 20, 30 and 40 wt% BNKT content and their dielectric and electrical properties were investigated. The energy harvester with 40 wt% BNKT achieved the highest dielectric constant and conductivity, whereas the device with 30 wt% BNKT ceramic generated the highest open circuit voltage of about 11 V under periodic compressive force of 20 N. These results imply that lead free BNKT:PDMS composite may be applied in pressure sensors and various energy harvesting devices.