X‐ray photoelectron spectroscopy of alkali germanate glasses

Abstract Several alkali germanate glasses of molar composition (100 − x )GeO 2 · x M 2 O (M = Na, with 0 ⩽ x ⩽ 35, or M = Cs, with 0 ⩽ x ⩽ 30) were prepared by melting, and their XPS spectra were recorded and analysed as a function of the alkali content. The simultaneous presence of bridging oxygen (BO) and non‐bridging oxygen (NBO) atoms was evaluated in both glass systems. In order to clarify the role of the alkali ions on the formation of NBO species, a series of different alkali germanate glasses were analysed (M = Na, K, Rb, Cs) for a particular glass composition 70GeO 2 ·30M 2 O. This comparison revealed that the percentage of NBO atoms increased upon insertion of the heavier alkali ions. Some explanations are proposed to account for the ways in which the different alkali ions modify the structure of these germanate glasses, in connection with the so‐called germanate anomaly . Copyright © 2002 John Wiley & Sons, Ltd.