EXAFS Study of Silver and Rubidium Environments in Silicate Glasses

In order to study local order around Ag and Rb ions in ionexchanged glasses EXAFS experiments were performed after thermal annealiigs 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 Kedge spectra present anomalous oscillations which can be ascribed to multi-electron excitations [ls3d]. 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.