Study of the effect of the substitution of Fe by Ti on the microstructure and the physical properties of the perovskite system La0.67Ca0.2Ba0.13Fe1−xTixO3 with x = 0 and 0.03 at low temperatures

Abstract

La_0.67Ca_0.2Ba_0.13Fe_1−xTi_xO₃ samples (x = 0 and 0.03) were synthesized by the auto-combustion method. Analysis of XRD diffractograms revealed that these compounds crystallize in the cubic system with the space group Pmm. The dielectric properties have been studied in the 10²–10⁶ frequency range and the 120–280 K temperature range. Analysis of AC conductivity shows that the conduction mechanisms are of polaronic origin and that they are co-dominated by the NSPT and OLPT models. The monotonic increase in conductivity with increasing temperature results from the reduction of defect centers and the increase in charge carrier mobility. Such variation is consistent with impedance variation at different frequencies and temperatures indicating semiconductor behavior. Nyquist diagrams are characterized by the appearance of semi-circular arcs. These spectra are modeled in terms of equivalent electrical circuits confirming the contribution of grains (R_g//CPE_g) and grain boundaries (R_gb//CPE_gb). The dielectric analysis showed an evolution of the dielectric constant in accordance with Koop's theory and the phenomenological model of Maxwell–Wagner. The low conductivity and the high values of the real permittivity at low frequency make our compounds potential candidates for energy storage and applications for electronic devices and microwaves.