Electrical conductivity and dielectric behaviour of nanocrystalline La_0.6Gd_0.1Sr_0.3Mn_0.75Si_0.25O₃

Abstract

An La_0.6Gd_0.1Sr_0.3Mn_0.75Si_0.25O₃ ceramic was prepared <i>via</i> a solution-based chemical technique. X-ray diffraction study confirms the formation of the compound in the orthorhombic structure with the <i>Pnma</i> group space. Dielectric properties have been investigated in the temperature range of 85-290 K with the frequency range 40 Hz to 2 MHz. The conductivity spectra have been investigated by the Jonscher universal power law: <i>σ</i>(<i>ω</i>) = <i>σ</i> _dc + <i>Aω</i> ^<i>n</i> , where <i>ω</i> is the frequency of the ac field, and <i>n</i> is the exponent. The deduced exponent '<i>n</i>' values prove that a hopping model is the dominating mechanism in the material. Based on dc-electrical resistivity study, the conduction process is found to be dominated by a thermally activated small polaron hopping (SPH) mechanism. Complex impedance analysis (CIA) indicates the presence of a relaxation phenomenon and allows us to modelize the sample in terms of an electrical equivalent circuit. Moreover, the impedance study confirms the contribution of grain boundaries to the electrical properties.