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

Abstract

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 R[Formula: see text]c 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 (ε″) showed a compositional dependence, indicating the prevalence of inter-grain conductive contribution and microstructural features which can be interpreted by the Maxwell–Wagner process.

Keywords

• Polaron hopping
• manganite
• impedance spectroscopy
• dielectric properties