A NEW METHOD TO STUDY COMPLEX MATERIALS IN SOLID-STATE CHEMISTRY - APPLICATION TO CHALCOGENIDE MATERIALS

We show that a combined application of Mossbauer spectroscopy and othe r experimental tools such as X-ray photoelectron spectroscopy, X-ray a bsorption spectroscopy and nuclear magnetic resonance provides a coher ent picture of the local electronic structure in chalcogenide material s. In order to develop this idea we propose an analysis of the Sn, Sb and Te local electronic structures for three different systems of mate rials. The first example concerns the In-Sn-S system. We show that Li insertion in In16Sn4S32 leads to changes of the Sn oxidation states fr om Sn(IV) to Sn(II). The second example concerns materials of the Tl-S b-S system. We show that variations of the Sb-121 Mossbauer isomer shi ft and surface of the first peak of the X-ray absorption spectra at th e Sb Lm edge can be linearly correlated because of the main influence of the Sb 5s electrons. This is explained by changes in the local envi ronment of the Sb atoms. The last example concerns the crystalline pha ses of the Tl-Sn-Te system. The formal oxidation numbers of the Te ato ms are determined from Te-125 Mossbauer spectroscopy and X-ray photoel ectron spectroscopy. They ate related to the different types of bonds involving the Te atoms in the Tl-Sn-Te compounds.