Textured Lead-Free Piezoelectric Ceramics for Flexible Energy Harvesters

Abstract

A lead-free (K,Na)NbO3-based piezoelectric ceramic is textured along the (001) direction using the NaNbO3 (NN) seeds. The composition 0.96(K0.5Na0.5)(Nb0.965Sb0.035)O3–0.01CaZrO3–0.03(Bi0.5K0.5)HfO3 (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, d 33 ∼ 590 pC/N, k 31 ∼ 0.46, and d 31 ∼ 215 ×10–12 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 (V oc ∼ 25 V), current (I ∼ 0.4 μA), and power density (P D ∼ 5.5 mW/m2) (R L of 10 MΩ) in the off-resonance frequency regime. In comparison to the random ceramic KNN-0NN-based F-PEH (V oc ∼ 8 V and I ∼ 0.1 μA), the textured F-PEH significantly outperformed energy harvesting capability due to the large figure-of-merit value (d 31 × g 31) ∼ 3354 ×10–15 m3/J. This work provides a methodology for texturing lead-free materials and further implementing them in flexible energy harvesting devices and sensors.

A poly(L-lactic Acid)-based flexible piezoelectric energy harvester with micro-zigzag structures

“…This can also be attributed to the inherent weak piezoelectric properties of pure PLLA, although these properties can be enhanced through appropriate means, which are currently undergoing intensive research [47,48], and using other flexible piezoelectric materials such as PVDF. Furthermore, PEH designs exist to transform piezoelectric ceramics into flexible piezoelectric layers [4,49]. In general, the design of a flexible beam is still an effective way to reduce the resonant frequency of PEH.…”

3D Printing of Flexible BaTiO3/Polydimethylsiloxane Piezocomposite with Aligned Particles for Enhanced Energy Harvesting

“…Internet of Things (IoT) and wearable electronics have attracted much attention in sensing technology; − however, unsustainable power supply for such sensors has become a serious challenge for their applications. − Traditional power-generation strategies are restricted by lifetime and frequent replacement. − Piezoelectric energy harvesters can convert ambient mechanical energy into electrical energy through a piezoelectric effect. − Piezoelectric ceramics and polymers are mainly used for piezoelectric energy harvesting. , The applications of piezoelectric ceramics, such as lead zirconate titanate (PZT) and barium titanate (BaTiO 3 ), in flexible wearable electronics are still restricted due to their high brittleness, poor flexibility, and low durability. − On the contrary, piezoelectric polymers, especially poly­(vinylidene fluoride) (PVDF) and copolymers, are promising candidates for flexible electronic devices due to their excellent flexibility and thermal stability. , …”