S K beta x-ray fluorescence spectra of the Tl-2-S-Sb2S3 chalcogenide system

The sulphur 3p valence states of Sb2S3, Tl3SbS3, TlSbS2, TlSb3S5, TlSb5S8, and Tl2S of the Tl2S-Sb2S3 system have been investigated by means of the S K beta (3p --> ls) x-ray emission band. TlSb3S5 and TlSb5S8 were also studied in the glassy phase. Synchrotron-radiation-induced fluorescence was used. The spectra are discussed in terms of bonding between the sulphur atoms and their nearest neighbours with the help of tight-binding calculations. We observe significant differences among the S 3p states of all these materials, including between the crystalline and glassy phase of TlSb3S5. The variations in the S K beta bandwidth and shape clearly reflect the sensitivity of the S 3p states to the local environment and indicate that the valence densities of states are mainly influenced by local order.