X-ray photoelectron spectroscopy (XPS) used as a structural and chemical surface probe on aluminosilicate minerals

The XPS spectra of single crystals of andalusite, kyanite, pyrope and K-feldspar, and pressed powder pellets of andalusite and pyrope, have been investigated. XPS yields accurate and reproducible chemical information on the near surface of these minerals. For kyanite, although the chemical composition is close to being stoichiometric, the composition of a cleaved kyanite surface is richer in Si. The chemical environments for the major components in aluminosilicate minerals exhibit a photoelectron chemical shift that is accurately measurable. Substitution of Si by Al in the tetrahedral site is only evident in one peak (the Ols peak). This peak can be split into its main components: Al-O-Si, Si-O-Si, non-bridged oxygen and adventitious material. However, the fitting of the Ols photopeaks suggests that the surface chemical oxygen bonding requirements cannot be directly compared to the bulk material, and other techniques are necessary.