Mossbauer studies of cation distribution in natural chromites from Boula-Nausahi igneous complex, Keonjhar district, Orissa, India

Mossbauer spectroscopic studies of the natural chromites obtained from four iron ore bands in the Boula-Nausahi igneous complex are presented. The res ults are quite different from those obtained for the. natural chromites fro m other Indian sites. The chemical composition and the lattice parameters v ary systematically in the four bands studied. The particle size decreases a s the Cr/Fe, ratio decreases. The structure of the paramagnetic samples are close to the ideal FeCr2O4 structure with small inversion. The B-site iron shows sharp Mossbauer lines with isomer shift and quadrupole splitting sho wing good correlation with the Cr/Fe ratio. The A-site iron experiences a d istribution of electric field gradient which may be, approximated by a few discrete quadrupole doublets. The chromite with Cr/Fe=0.35 shows a magnetic ally split spectrum possibly affected by superparamagnetic relaxation. (C) 2001 Elsevier Science BV All rights reserved.