Dielectric properties and conduction mechanism of La0.7Sr0.25Na0.05Mn0.95Al0.05O3 perovskite manganite

The present paper reports on the effects of Aluminum-doping on the micro-structural and dielectric properties of La0.7Sr0.25Na0.05Mn0.95Al0.05O3 ceramics. The analyses of the X-ray diffraction data by the Rietveld refinement technique confirmed the formation of a rhombohedral phase in the R3 space group. The dielectric properties were analyzed by the complex impedance spectroscopic techniques in a wide temperature extent and a spectral range between 2 kHz and 1 MHz. The Nyquist diagram with a single semicircular arc is explained by the contribution of two conducting phases associated with the effects of grains and grain boundaries. The conductivity spectrum obeyed Jonscher ' s power law and the conduction mechanism was attributed to the correlated barrier hopping mechanism. The dielectric parameters such as the dielectric constant (epsilon(n)) showed a compositional dependence, indicating the prevalence of inter-grain conductive contribution and microstructural features which can be interpreted by the Maxwell-Wagner process.