Nanostructured (CoxFe1–x)3–yO4spinel – mechanochemical synthesis

Abstract

Abstract The effects of wet-milling mixtures of α-Fe2O3 and cobalt hydroxide Co(OH)2 over a range of Co/Fe ratios for 215 h have been investigated by neutron diffraction and Mossbauer spectroscopy. The starting materials were mixed according to the stoichiometric formula (CoxFe1–x)3O4 for values of x = 0.037, 0.071, 0.133, 0.234 and 0.380 (i. e., from ≈Co0.1Fe2.9O4 to the cobalt spinel CoFe2O4). These studies reveal the formation of a nanostructured, mixed Co–Fe spinel phase with non-stoichiometric composition (CoxFe1–x)3–yO4; the defect spinels have refined values xc = 0.04, 0.08 and 0.14 for the mixtures with the lowest Co content (x = 0.037, 0.071 and 0.133) and defect concentrations in the range y ≈ 0.1–0.2. Both the spinel phase and un-reacted α-Fe2O3 are found to occur in the neutron diffraction patterns and Mossbauer spectra for the high Co content mixtures x = 0.234 and x = 0.380. Rietveld refinements of the neutron data indicate that the Co atoms predominantly occupy the octahedral B sites with v...