Abstract
The chemical state of oxygen in Ag +/Na + ion-exchanged sodium silicate glass was investigated using X-ray photoelectron spectroscopy and 29Si nuclear magnetic resonance spectroscopy. Ion-exchange treatment was performed on 34Na 2O66SiO 2 glass at temperatures well below T g of the mother glass, giving glass samples with various Ag +/Na + ratios. The glass transition temperature decreased about 150 K with increase in Ag + concentration, accompanied by the simultaneous decrease of the thermal expansion coefficient by about 50%. Large changes in O1s XPS spectra were observed; the bridging and non-bridging oxygen peaks shifted toward larger binding energies, and the ratio of non-bridging oxygen (NBO) to bridging oxygen decreased with increasing Ag + concentration. This trend revealed that the increased covalency of Ag +O nb bonds decreased T g and the thermal expansion coefficients. 29Si-NMR results showed that Q 3 units decreased while Q 2 units increased without accompanying Q 4 units. These results suggested that two coordinated Ag + ions with non-bridging and bridging oxygen would be formed in the sample glasses.
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