Bonding-state characterization of the constitutent elements of silicate minerals by X-ray photoelectron spectroscopy

Abstract

X-ray photoelectron and X-ray-induced Auger electron spectra of silicate minerals have been measured. The systematic shifts of the photoelectron binding energies of Si, O and tetrahedrally coordinated Al ions in the silicate framework suggest that the negative charge on the framework is delocalized over these ions. On the other hand, it is deduced from the photoelectron binding and Auger electron kinetic energies that the octahedrally coordinated Al and Mg ions in the silicate mineral are not subject to a strong effect from the negative charge on the silicate framework. A comparison of the Na 1s binding and KL₂₃L₂₃ Auger kinetic energies of the exchangeable Na ion in the silicate mineral with those of sodium halides reveals that the bonding state of the exchangeable Na ion is comparable to those of Na ions in sodium chloride and fluoride.