Microstructural Characterization of Mechanically Activated ZnO-Cr2O3 System

An equimolar mixtures of starting ZnO and Cr2O3 powders were mechanically activated by grinding using a planetary ball mill for various periods of time (40 to 320 minutes). Formation of nanocrystalline ZnCr2O4 as normal spinel structure at room temperature is detected in all samples after ball-milling. A detailed XRD structural analysis (lattice parameters, site occupancy, the average primary crystallite sizes, crystal lattice microstrains) is realized by the pattern decomposition technique, performed in accordance with the procedure based on Rietveld software KOALARIET-XFIT. Due to the importance of cation distribution on the chemical and physical properties of spinels, a study of site occupation factors of ZnCr2O4 spinels has been undertaken. Evaluated spinel non-stoichiometry is a result of the ZnO dissolving in the stoichiometric ZnCr2O4. The manner of ZnO incorporation into the spinel lattice is performed according to the procedure based on calculation of both formation and attachment energies. The calculation based on the atomistic methods for the simulation and description of the perfect and defect spinel ZnCr2O4 crystal lattice has been made togheter with the determination of the individual structural defects.