Summerfield scaling model and conduction processes for the determination of the transport properties of the Ba0.25Sr0.25Fe2.5O4 ceramic

The conductivity spectra of the iron oxide Ba0.25Sr0.25Fe2.5O4 revealed that sample exhibits a semi-conductor behavior within the temperature and frequency. Based on the direct current analysis, charge carrier transport was assisted by a disorder energy below θD/4. For θD/4≤T≤θD/2, electrical conductivity was attributed to the contribution of the Mott-VRH mechanism. However, for T≥θD/2, conduction phenomena were supported by the thermal activation of the small polaron hopping mechanism. At higher frequencies, the electrical characteristics of our sample were clarified through the application of a superlinear power law. The contributions of different conduction processes were predicted using temperature dependent frequency exponents. The hopping energy was found to decrease as the frequency increased, a trend that can be linked to variations in the polaron radius. The impedance results validate the involvement of the resistive grain boundary in the electrical properties and indicate the presence of multiple electrical relaxation phenomena in the Ba0.25Sr0.25Fe2.5O4 sample.