(K,Na)NbO₃-LiNbO₃ nanocube-based flexible and lead-free piezoelectric nanocomposite energy harvesters

The research on harvesting the wasted mechanical energy and using it as a useful energy source has been in the spotlight. Conventional ceramic-based devices have disadvantages such as mechanical brittleness and high-temperature processing. To overcome these weaknesses, the piezoceramic materials mixed with polymer matrix have been studied to produce flexible piezoelectric devices. Herein, a piezoelectric composite film is fabricated by mixing lead-free 0.942[Na_0.535 K_0.480NbO₃]-0.058LiNbO₃ (KNNLN) nanocube powder with polydimethylsiloxane (PDMS) matrix. KNNLN nanocube powder is synthesized by a solid-state reaction method, which can typically present outstanding stoichiometric composition and perovskite crystalline structure. The cube-shaped particles are thought to show higher stress concentration at corners and edges of the nanocube than spherical particles when external mechanical input is applied. The flexible KNNLN nanocube–PDMS nanocomposite device generates the piezoelectric signals of ~ 28 V and ~ 220 nA during bending motion, which is a high-performance energy harvesting efficiency compared to previous KNN-based flexible piezoelectric composites generators. KNNLN nanocube-based composite can replace toxic lead-based nanocomposites for future flexible devices such as eco-friendly self-powered energy harvester and biocompatible sensor.