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

Abstract

Mossbauer spectroscopic studies of the natural chromites obtained from four iron ore bands in the Boula-Nausahi igneous complex are presented. The results are quite different from those obtained for the. natural chromites from other Indian sites. The chemical composition and the lattice parameters vary systematically in the four bands studied. The particle size decreases as 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 showing good correlation with the Cr/Fe ratio. The A-site iron experiences a distribution of electric field gradient which may be, approximated by a few discrete quadrupole doublets. The chromite with Cr/Fe=0.35 shows a magnetically split spectrum possibly affected by superparamagnetic relaxation. (C) 2001 Elsevier Science BV All rights reserved.