The crystal chemistry of Fe-bearing sphalerites: an infrared spectroscopic study

Iron substitution into sphalerite, ZnS, has been studied systematically by infrared spectroscopy. A range of natural and synthetic compositions, ([Zn.sub.1-x][Fe.sub.x])S, 0 [less than or equal to] x [less than or equal to] 0.24, were examined. The IR spectrum of pure ZnS contains a single strong absorption band at 320 [cm.sup.-1]. With addition of FeS, the spectra become broader and shoulders appear. For compositions [less than or equal to] 9 tool% FeS, a splitting of the main peak occurs, and the spectra show two absorption maxima at approximately 300 and 315 [cm.sup.-1], respectively. The observation of such extra features does not correspond to the usual behavior observed in other ternary mixed crystals, where either one-, two-, or mixed-mode behavior is observed. The spectra can be deconvoluted into up to three peaks, main Peaks A and B at around 300 and 315 [cm.sup.-1], respectively, and a shoulder at around 330 [cm.sup.-1] (Peak C). The positions and area of the peaks do not change significantly with increasing Fe content. The peak at 315 [cm.sup.-1] is the main absorption peak of the host ZnS structure, and the peak at 300 [cm.sup.-1] is an impurity induced mode. An effective linewidth parameter [[DELTA].sub.corr] was determined by autocorrelation analysis for each spectrum, but there are no obvious trends in the values of [[DELTA].sub.corr] that can be interpreted in terms of an inhomogeneous distribution of Fe within the sphalerite structure. Keywords: Fe-bearing sphalerites, infrared spectroscopy, autocorrelation analysis, solid solution