EXAFS study of silver and rubidium environments in silicate glasses

In order to study local order around Ag and Rb ions in ion-exchanged glasses EXAFS experiments were performed after thermal annealings at different temperatures below and above the glass transformation temperature; By means of Ag K-edge spectra three coordination spheres could be discussed. Whereas the two Ag-O distances remain unchanged during thermal treatments the Ag-Ag correlation exhibits the influence of the transformation of Ag ions to crystalline precipitations at elevated temperatures. The Rb K-edge spectra present anomalous oscillations which can be ascribed to multi-electron excitations [1s3d]. In order to evaluate the main EXAFS signal, these features were subtracted using absorption data of gaseous rubidium. The Fourier transforms display similar Rb-O bond lengths within the first sphere for both the ion-exchanged soda-lime and the disilicate glasses while relaxation phenomena modify the second oxygen sphere towards the disilicate structure.