Mossbauer, XPS and XAS spectroscopies: an efficient combination for the study of cristalline solids

Chalcogenide materials show very different electronic properties because of the diversity of their structures. The study of these properties often req uires the use of different and complementary techniques. We show that the c ombined application of the X-ray spectroscopy (XPS), X-ray absorption spect roscopy (XAS) and Mossbauer spectroscopy provides a consistent picture of t he electronic structure of the chalcogenide materials which can be analysed from theoretical tight-binding calculations. Two examples of chalcogenide materials are considered in this paper. The first example concerns sulphide materials of spinel structure : In16Sn4 S32. We show from the experimental results obtained Sn-119 Mossbauer spectr oscopy, XAS at the Sn L-1 edge and the XPS core levels and valence bands th at insertion of Li atoms in ln(16)Sn(4)S(32) leads to the reduction of tin atoms from Sn(IV) to Sn(II). We have found that the ratio of the two oxidat ion states is proportional to the amount of inserted Li atoms. The reductio n mechanism is explained from a tight-binding calculation. The second examp le concerns the crystalline phases of the Sb2S3-Tl2S system. In this system , the local structural environment of the Sb atoms strongly varies from Sb2 S3 to Tl2S. The experimental results obtained by Sb-121 Mossbauer spectrosc opy XAS at the L-III edge of Sb and XPS core levels and valence bands show strong variations of the Sb local electronic structure. These results are r elated to structural changes from a tight-binding calculation of the densit ies of states and the electronic populations. In particular, we show that t he Sb-121 Mossbauer isomer shift and the surface of the first XAS peak at t he Sb L-III edge can be linearly correlated. This correlation is explained from the strong influence of the Sb 5s electrons which can be related to th e stereochemically activity of the lone pair.