Frequency dependent energy storage and dielectric performance of Ba–Zr Co-doped BiFeO3 loaded PVDF based mechanical energy harvesters: effect of corona poling

Abstract

Bi_0.95Ba_0.05Fe_0.95Zr_0.05O₃ (BBFZO) nanoparticles were synthesized by a sol–gel technique to develop a filler material with lower leakage current and oxygen vacancies compared to the host BiFeO₃. In this work, we report the enhanced dielectric, ferroelectric, energy storage and energy harvesting performance of BBFZO incorporated PVDF composites. 15 wt% BBFZO loaded PVDF (15BBFZO) exhibited improved polarity (F(EA) = 77.42%) compared to neat PVDF (F(EA) = 37.01%). At an applied field of ∼14 kV cm⁻¹ (1 Hz), this film (15BBFZO) exhibited a maximum energy storage density of 151.18 μJ cm⁻³ (at 1 Hz). Upon repeated human finger tapping, an average open circuit peak to peak a.c. voltage (V_OC) ∼ 20 V was obtained from 15BBFZO. A comprehensive study of frequency dependent D–E loops and an extensive study of the effect of electrical poling on the output performance of the developed composite films have been performed. An improvement of the dipolar polarization was established through a frequency dependent D–E loop study of unpoled and poled 15BBFZO and from other experiments. After poling the energy storage density and V_OC of 15BBFZO were 154.66 μJ cm⁻³ (at 1 Hz) and ∼30 V, respectively. After rectification this output electrical signal was able to charge a 10 μF commercial capacitor up to ∼5.5 V. After poling, the energy storage efficiency (η) of 15BBFZO also improved from 52.49% to 67.85% (at 1 Hz). The frequency dependence of the storage efficiency for all the samples has also been extensively investigated here. At 1 kHz, η improved to 93.30% for poled 15BBFZO.