THE PHOTOELECTRON-SPECTRA OF SOME TL-SB SULFOSALTS

The results of X-ray induced photoelectron spectroscopy (XPS) experime nts on several phases of the ternary system Tl-Sb-S are reported. The binding energies of the inner S, Sb and Tl electrons increase with inc reasing quantities of Sb and decreasing amounts of Tl in these compoun ds. This is explained by the influences of the proportions of the bond ed metals on the effective electron affinity of S. The,higher proporti ons of the more electronegative element bonded to S cause the increase of its effective electron affinity. The results for Tl2S (carlinite), Tl3SbS3, TlSbS2 (weissbergite), TlAsS2 (lorandite) and Sb2S3 (antimon ite) can be interpreted in this way. The results for Tl4S3 suggest a p redominantly covalent character of bonding for both Tl(III) and Tl(I), which are present in this sulfide. From comparison with Tl3SbS4 it co uld be supposed that Tl(Ill)-S bond has a more covalent character than Sb(V)-S bond. The results for Tl3SbS4 are in agreement with crystal s tructure data and the results of Moessbauer spectroscopy. For AsS (rea lgar) the binding energies of the inner electrons of As and S signific antly increase, showing that the electrons in molecular orbitals are l ess strongly bonded to individual atoms, as compared to pure elements. The results for the amorphous TlSb5S8 (corresponding in composition t o parapierrotite) suggest that in amorphous compound the Tl-S bonding is stronger and the coordination of Tl more regular than in a crystall ine one.