Local Ordering Around Tetrahedral Co~(2+) in Silicate Glasses

摘要

Alkali lime silicate glasses containing 5 wt% of CoO were investigated by Co K-edge XANES and EXAFS and optical absorption spectroscopy. Our results reveal the presence of tetrahedral Co~(2+) connected with the glass network, with a ~(IV)Co-O-Si angle of 134°. Changing the alkali from K~+ to Na~+ induces an increase of the local disorder around Co~(2+) , as shown by a decrease of the contribution from the second neighbors in the EXAFS signal. We propose two models for interpreting the structure of the second shell of neighbors. Our results provide a structural basis for rationalizing the optical properties of Co~(2+) species in glasses.