Preparation and characterization of phosphate glasses containing titanium and vanadium

Na5−xTi1−xVx(PO4)3 (0 ≤ x ≤ 1) phosphates glasses have been obtained in air by direct fusion of Na2CO3, TiO2, V2O5 and (NH4)2HPO4. Vitreous Na5Ti(PO4)3 is colourless while the glasses containing vanadium are green, due to the reduction of V5+ to V4+. Glass transition and crystallization temperatures (Tg, Tc) decrease when the amount of vanadium increases. EPR, Raman and UV–vis spectra have been investigated. The results are consistent with the presence of V4+ ions in distorted octahedra with very strong VO bond.