ALBERT

Description: INTRODUCTION Spectroscopic methods are powerful means to obtain information on the electronic or local structure of materials. By these methods, constraints can be provided on the chemical state, crystal chemistry or, in non-crystalline materials, the coordination environment or complexation of a given element. In this chapter, we focus on spectroscopic techniques that provide direct insight into the sulfur (S) species present in glasses and melts and which are applicable at the sulfur concentrations usually found in glasses (mostly below 1–2 wt%). Methods that are potentially suitable for this task are i) the wavelength analysis of X-ray emission spectra (mostly using the electron microprobe), ii) X-ray absorption spectroscopy, iii) 33S NMR and iv) Raman spectroscopy. For compounds such as sulfides or sulfates, containing S as a major component, further methods such as optical absorption spectroscopy in the UV-visible frequency range (UV-VIS) or electron spin/paramagnetic resonance (ESR or EPR) spectroscopy (e.g., Ross 1974; Wincott and Vaughan 2006) are useful. However, these two techniques provide only an indirect view on sulfur because they actually probe the cations, which are often transition metals. In compounds where S is a major component, these data also provide information on the sulfur species, because the cations are linked to S as an anion. In glasses, where S is only a minor component and cations are mostly coordinated by oxygen, it is difficult to link the observations made on the cation to the S species. Nevertheless, there are some studies on glasses where the additional information by UV-VIS or ESR spectroscopy was used to constrain possible species of sulfur in the glass (e.g., Beerkens 2003; Bingham et al. 2010). Here, only very brief introductions to the spectroscopic techniques will be provided. For a more detailed introduction to the spectroscopic techniques introduced here the reader is...