Preliminary XAS investigations on some phases of the Cu-Sn-S system

X-ray absorption spectroscopy investigation has been carried out at the Cu K edge on synthetic materials belonging to the ternary Cu-Sn-S system. In particular, Cu3SnS4 nanocrystalline powders, obtained through a solvothermal approach, and Cu4SnS4 microcrystalline powders, obtained through standard solid state reactions, were investigated. From the XANES spectra, Cu is confirmed to be monovalent in both samples, thus implying a complex mechanism to achieve charge balance in Cu3SnS4. In this sample, the Cu-S EXAFS distance is found surprisingly short, and this suggests that Cu ions could be shifted outside the barycentre of the tetrahedra