Engineering of Polystyrene/BiFeO3 0–3 Thin Film Nanocomposites for Mechanical Energy Harvesting

This work describes impact of concentration of BiFeO₃ submicrometric particles on piezoelectric performance and structural characteristics of 0–3 polymer composites with a polystyrene matrix. Bismuth ferrite particles are fabricated using reverse co-precipitation method, followed by ultrasonic dispersion in a solvent to break up agglomerates formed during sintering, resulting in particles with a size of ≈200 nm. It is found that concentrations higher than 10 wt% BiFeO₃ lead to a disturbance in natural organization of polystyrene. The hindered organization of side-groups by submicrometric filler, occurring during solvent evaporation, strongly affects the mechanical properties of the finalcomposite, significantly increasing Young's modulus and tensile strength, but decreasing elongation. Such behavior is detected and described for the firsttime in literature. Piezoelectric examinations show that the thermal depolarization of nanogenerators has a different impact depending on the amountof piezoelectric phase. The study reveals that a voltage of over 4.8 V is generated when dynamic air pressure is applied at 11.54 bar for the composite containing only 2.5 wt% BiFeO₃. For composites with 10% weight fraction or lower, decrease in generated voltage after thermal depolarization is about 24%, while for higher weight fractions (15 and 20 wt%) the decrease is around 35%.