Spinel solid solutions in the Li-Fe-Mn-O system

The ranges of Li-Fe-Min composition in which single-phase microparticulate spinel oxides are formed by heating in air were determined. The aim was to reevaluate previously published reports on binary solid solutions between L iFe5O8 and Li-Mn-O spinels by covering the whole possible range of (Li, Fe, Mn)(3)O-4 spinels with Mn valence higher than 3. To sensitively detect pos sible heterogeneity of the elemental distribution or phase composition, che mical and X-ray powder diffraction analyses were used, temperature dependen ce of magnetic susceptibility was obtained for samples rich in Fe, and elec trochemical reductive dissolution was studied by means of voltammetry of mi croparticles. Instead of a continuous series of solid solutions, three regi ons were found with different dependence of lattice parameters on elemental composition. A region of nonuniform solid solutions was found at Fe/(Fe+Mn )>0.4 and Mn valence >3.2. (C) 2001 Academic Press.