Local order changes induced in calcium–sodium–phosphate glasses by transition metals

The structural effects caused by transition metal oxides (TMO) added to calcium–sodium–phosphate glasses are investigated with respect to the local order up to atomic environment using differential thermal analysis (DTA) and X-ray photoeffect spectroscopy (XPS). Reference data are collected from 50P2O5·30CaO·20Na2O host glass. Different influences of TMO on the crystallisation temperature and glass stability are observed if Ag2O or Fe2O3 is added to the host glass. The melting temperature is diminished by Ag2O and is enhanced by Fe2O3. The data point out higher values for glass stability of iron containing glasses. XPS data support that in this glass system the oxidation state of iron ions is 3+ and Fe2O3 acts as a glass network former. By TMO addition the valence band of the host glass is shifted from 2.6 eV to negative values of the binding energy.