EXAFS and XANES investigations of sodium borate glasses containing copper ions

Extended x-ray absorption fine structure and x-ray absorption near edge structure measurements showed that the copper ions in the glasses are coordinated by four square planar oxygen ions. The nearest Cu-O bond length decreases with increasing Na₂O content and shows a minimum at 30 mol% Na₂O. It is suggested that the next nearest peaks in the radial distribution functions of low Na₂O glasses are to be attributed to oxygen ions in the second shell as well as boron ions, whose intensity decreases with increasing Na₂O content. In the XANES spectra, there is a correlation between the normalised absorption intensity of the peak around 8981-8983 eV and the cuprous ion content.