Composition, Microstructure, and Electrical Properties Control of the Powders Synthesized by Sol-Gel Auto-Combustion...

Nanocrystalline lithium ferrite Li _0.5 Fe _1.7 Mg _0.8 O ₄ powders were synthesized by the sol-gel auto-combustion method from the corresponding metal nitrates using citric acid as fuel.The results from XRD, SEM, and AC electrical conductivity studies are summarized as follows: The results of XRD analysis showed that all the samples were formed in single-phase cubic spinel structure at different annealing temperatures from 300 to 700 °C for 2 h. The lattice parameter was found to decrease on increasing the temperature. The microstructure of lithium ferrite powders was temperature dependent. The particle size was increased with the annealing temperature. AC electrical properties were investigated using the super-linear power law and activation energies were calculated for all compositions. The electron mobility in Li _0.5 Fe _1.7 Mg _0.8 O ₄ samples ranged from 0.05 to 0.29 eV, which clearly indicated that the present lithium ferrites have semiconductor-like behavior. The frequency exponent "s" of lithium ferrite lies in the range 0.5 < s < 1, which confirms the electron hopping between Fe ^2 + and Fe ^3 + ions.