Effect of selenium addition on network connectivity in P2O5-CaO-MgO-Na2O glasses

A new glass system xSeO2(1-x)[40P2O5-30CaO-20MgO-10Na2O] with nominal concentration of SeO2 ranging between 0 and 20 mol% was obtained by melting method. The amount of selenium determined on samples surface is much lower than that expected according to the added SeO2 amount, and this is due first to selenium volatility during melting. The Fourier transform infrared and Raman results evidence the glass network depolymerisation induced by progressive addition of selenium. The depolymerisation effect occurs more pronounced on samples surface than in their inside, as indicated by X-ray photoelectron spectroscopy analysis with respect to the dependence of bridging and non-bridging oxygens on selenium content.