Characterization of Electrical Properties of Li(FexAl1−x)5O8 Solid Solutions by Impedance Spectroscopy

To examine polaronic transport properties in Li(FexAl1−x)5O8 spinel solid solutions, a scaling analysis for their conductivity spectra and modulus spectra was performed. As in the case of ionic conductors, two significant parameters of a crossover frequency and a power‐law exponent were extracted from the conductivity spectra which displayed the universal dynamic response behavior. Both the mobility and the concentration of carriers were successfully determined from the crossover frequency. The power‐law exponent and the stretching parameter obtained from the modulus spectra varied with composition, implying that the increase in Fe concentration would enhance the Coulomb interactions between small polarons.