Poly(L-lactic acid)/lithium ferrite composites: Electrical properties

Composites of lithium ferrite, LiFe5O8 (LFO) particles, dispersed in the biopolymer poly (L-lactic acid) (PLLA) were prepared by solvent casting in concentrations from 0 to 19.5 wt%, which were characterized by thermal analysis (TGA/DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and impedance spectroscopy (IS). As neat PLLA, all obtained composites are semi-crystalline, but the crystallinity decreasing with percentage LFO increase. Moreover, a good dispersion of LFO particles was found, with no interactions with the polymeric matrix. For the lower LFO content (3.5 wt%), dynamical relaxation processes were probed by IS, allowing to disclose subtle differences relative to the neat matrix. Above that concentration, the conductivity dominates and follows the percolation law above a quite low volume concentration of conductive particles (5.45%v/v). Therefore, depending on the LFO content different applications can be envisaged: energy storage for low concentrations and electromagnetic radiation shielding for concentrations above the percolation threshold.

Automated summary

Composites of LiFe5O8 (LFO) particles dispersed in PLLA were prepared by solvent casting, showing a decrease in crystallinity with increasing LFO content, good dispersion of LFO particles, and no interaction with the polymeric matrix. Impedance spectroscopy revealed dynamic relaxation processes at lower LFO content, while conductivity dominated at higher concentrations following the percolation law. Applications can vary depending on LFO content, with energy storage for low concentrations and electromagnetic radiation shielding for concentrations above the percolation threshold.