Strontium-substituted La_0.75Ba_0.25−xSr_xFeO₃ (x = 0.05, 0.10 and 0.15) perovskite: dielectric and electrical studies

La_0.75Ba_0.25−xSr_xFeO₃ perovskite compounds with different strontium concentrations were synthesized via the sol–gel method. X-ray diffraction (XRD) data indicated that all obtained samples crystallize in the orthorhombic structure with the Pnma space group. The dielectric properties of these samples, using complex impedance spectroscopy technique have been carried out as function of frequency and temperature as well. An adequate electrical equivalent circuit has been used to evaluate the grain and grain boundary contributions in complex impedance results. Furthermore, the AC conductivity spectra obey to Jonscher's universal power law. The behavior of the exponent "S" suggests that the conduction mechanism follows the overlapping large polaron tunneling (OLPT) process for x = 0.05, while for both compounds x = 0.10 and x = 0.15 the non-overlapping small polaron tunneling (NSPT) is the applicable model. The behavior of ε″ as a function of both frequency and temperature has been described by Giuntini model.