Intrinsic piezoelectric characterization of BiFeO3 nanofibers and its implications for energy harvesting

Perovskite oxide-based ferroelectrics are interesting in energy applications due to their electrical and optical properties. Nanostructuring opens new paths to increase the surface-to-volume ratio, porosity, and mechanical flexibility as compared with bulk materials, improving and tuning properties associated with piezoelectricity, ferroelectricity, piezoelectrochemistry, electrical conductivity, and catalysis. To elucidate the impact of nanostructuration, in piezoelectricity, we characterized one of the most promising perovskite materials, bismuth ferrite (BiFeO3), in the form of 1D nanostructures, namely nanofibers. A set of BiFeOx precursor nanofibers were electrospun from a chemical sol and calcined at 600 °C to obtain the final BiFeO3 nanofiber structure. By scanning the nanofiber sample, the piezo-generated charge at the nanoscale level was studied by Direct Piezoelectric Force Microscopy (DPFM). Our results report that the direct piezoelectric coefficient of the polycrystalline nanofibers is d33 = 11 pC/N, which corresponds to a smaller value as compared with epitaxial films, 22 pC/N for 60 nm films and 43 pC/N for 400 nm films. The diminishing of piezoelectric property characteristics is mainly attributed to the impact of nanostructuration. The nanofibers impose another clamping factor that decreases the BiFeO3 piezoelectric property, reducing their use as energy harvesters in favor of catalytic applications, water splitting, or photovoltaic applications.