Abstract
In V2O5-P2O5 glass system containing a large amount of V2O5, addition of Sb2O3 was very effective to improve the water durability. To clarify this effect, the influence of Sb2O3 addition on the glass structure was studied. The added Sb2O3 acted particularly on V-ions in the glass, and caused the following redox reaction. 2V2O5+Sb2O3→4VO2+Sb2O5 (2V5++Sb3+→2V4++Sb5+) Decrease in V5+ -ions forming a layered structure and increase in V4+ -ions not forming this structure were considered to transform the glass structure from layered to three-dimensional network, which prevented water molecules from penetration. Further, this structural transformation decreased the number of sites which were attacked easily by water molecules, i.e., quasi-double bonding oxygens and three-coordinate oxygens in V2O5, P-O-P bonds and non-bridging oxygens, and increased stable two-coordinate oxygens (bridging oxygens). Both of the structural transformation and the increase in bridging oxygens were considered to be effective to inhibit the erosion of V2O5-P2O5 glasses with Sb2O3 addition by water. Further, the addition of Sb2O3 did not increase the characteristic temperatures of glass remarkably, because packing density of oxygens remain unchanged by the addition.
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