Microstructure and positron annihilation studies of mechanosynthesized CdFe2O4

Nanocrystalline non-stoichiometric cadmium ferrite (CdFe2O4) has been synthesized by high-energy ball milling the mixture (1:1 mol%) of CdO and α-Fe2O3 at room temperature. Formation of nanocrystalline CdFe2O4as normal spinel structure has been noticed after ball milling the mixture for 5 h. The structural and microstructural evolution of CdFe2O4 caused by milling is investigated by X-ray powder diffraction. The relative phase abundances, particle sizes, r.m.s. strains, lattice parameter changes of different phases have been estimated employing Rietveld powder structure refinement analysis of XRD data. It appears that solid state diffusion of nanocrystalline CdO into α-Fe2O3 particles results in formation of nanocrystalline CdFe2O4 spinel. XRD data analysis indicates that the ferrite prepared by ball milling is a non-stoichiometric Cd-riched phase. Positron annihilation lifetime measurements on the milled samples indicate rise of defect density up to 5 h milling time and supports the formation of non-stoichiometric CdFe2O4 phase.