X-RAY-ABSORPTION STUDIES OF GE AND GA ENVIRONMENTS IN BAO-GA2O3-GEO2 GLASSES

The local structure surrounding Ge and Ga cations in BaO-Ga2O3-GeO2 gl asses has been studied using X-ray absorption spectroscopy. Based on c omparisons with results for crystalline standards, the Ge and Ga in al l the glasses are predominantly in tetrahedrally coordinated sites whi ch are disordered relative to the crystals. While bond length and coor dination stay fairly constant for all the glasses, disorder steadily i ncreases with BaO content, especially in the second shell surrounding Ge and Ga. Previously observed trends in certain macroscopic physical properties, therefore, cannot be explained by coordination changes but may be due to longer-range structural variation.