Microstructural properties, conduction mechanism, dielectric behavior, impedance and electrical modulus of La0.6Sr0.2Na0.2MnO3 manganite

Abstract

La0.6Sr0.2Na0.2MnO3 manganite was synthesized using sol–gel method. XRD pattern with Rietveld refinement indicates that sample crystallizes in the rhombohedral structure with $$R\overline{3}c$$ space group. The electrical conductivity analysis shows a metal–semiconductor transition temperature at TMS = 280 K for the sample. Dielectric constants decrease with frequency and their behaviors have been investigated according to the Maxwell–Wagner theory of interfacial polarization. An appropriate electrical equivalent circuit was used to analyze the Nyquist plots, and the results show that the conduction mechanism of the synthesized manganite is mainly due to the grain boundary contribution. The modulus analysis shows the presence of electrical relaxation phenomenon and non-Debye nature for the sample. The activation energy deduced from the conductivity analysis matches very well with the values estimated from the relaxation time and the grains boundary resistances. This indicates that relaxation process and electrical conductivity are attributed to the same defect.