Textured Lead-Free Piezoelectric Ceramics for Flexible Energy Harvesters.

A lead-free (K,Na)NbO-based piezoelectric ceramic is textured along the (001) direction using the NaNbO (NN) seeds. The composition 0.96(KNa)(NbSb)O-0.01CaZrO-0.03(BiK)HfO (KNN) is found to provide an excellent combination of electromechanical coefficients at room temperature. The textured composition with 5 wt % NN template (KNN-5NN) exhibits considerably improved electromechanical coefficients, ∼ 590 pC/N, ∼ 0.46, and ∼ 215 ×10 C/N, at room temperature. A flexible piezoelectric energy harvester (F-PEH) is fabricated using the textured KNN-5NN ceramic and tested under cyclic force. F-PEH exhibits enhanced output voltage ( ∼ 25 V), current ( ∼ 0.4 μA), and power density ( ∼ 5.5 mW/m) ( of 10 MΩ) in the off-resonance frequency regime. In comparison to the random ceramic KNN-0NN-based F-PEH ( ∼ 8 V and ∼ 0.1 μA), the textured F-PEH significantly outperformed energy harvesting capability due to the large figure-of-merit value ( × ) ∼ 3354 ×10 m/J. This work provides a methodology for texturing lead-free materials and further implementing them in flexible energy harvesting devices and sensors.