Super-linear frequency dependence of ac conductivity in nanocrystalline lithium ferrite

An attempt has been made to synthesize nanocrystalline high dense lithium ferrite, namely, Li0.5MxFe2.5 O--x(4) (M = Bi, Pb; x = 0, 0.02) by a solution combustion technique. Various characterization methods like XRD and TG-DTA were employed to validate the structure and phase purity. UV-vis diffuse reflectance spectroscopic studies were conducted to obtain the oxidation states of metal ions. Raman analysis was used to identify the phonon modes involved in specific atomic motions present in the synthesized materials. Morphology of sample surface was explored by electron microscope and elemental analysis was done by energy dispersive analysis. The nanocrystalline nature of the materials were confirmed through transmission electron microscopy. Strong temperature dependence of electron spin resonance linewidth was exhibited by the samples and a resonance field was observed for all the materials. Ac electrical properties were investigated using the super-linear power law and activation energies were calculated for all compositions. The conductivity data were consistent with an asymmetric double well potential model. (C) 2014 Elsevier B.V. All rights reserved.