Structural and colour changes induced by increasing amounts of vanadium oxide, V205, are presented for a new formulation of glass with composition 37Ca0.6Zr02.57Si02 (mol%). Property changes were evaluated by measuring density, chemical durability and micro hardness of glasses with increasing amount of vanadium oxide. Vanadium oxide imparts to the glass a light green colour, not dissimilar to that from chromium, at low content, while at higher concentration the colour changes to dark brown. Spectroscopic technique, VIS-NIR and ESR were used to identify the chromophore centres in terms of vanadium oxidation state and co-ordination which were subsequently correlated to property changes. Experimental evidence is reported for an equilibrium between two species, V5+ tetrahedral and V4+ tetragonally distorted octahedral.
