X-ray characterization and phase transformation kinetics of ball-mill prepared nanocrystalline Mg-Ni-ferrite at elevated temperatures

Nanocrystalline Mg-Ni-ferrite has been synthesized by high-energy ball milling the stoichiometric powder mixture of MgO, NiO and α-Fe2O3 and post-annealing the ball-milled powder at 1073 K. A non-stoichiometric and nanocrystalline ferrite phase is noticed to form just after 3 h of milling and the content of it increases with increasing milling time up to 25 h. Post-annealing of 8, 20 and 25 h milled powder at 1073 K for 1 h results in formation of stoichiometric Mg-Ni ferrite phase with range of crystallite size from sub-micron to nanometer. A stoichiometric ferrite phase with sub-micron-sized crystallites, is found to form by sintering the unmilled stoichiometric powder mixture at 1473 K for 3 h. Phase transformation kinetics in ball-milled, post-annealed and sintered samples are characterized by X-ray powder diffraction pattern analysis.