Vanadium in Borosilicate Glass

Abstract

Understanding the role of V 2 O 5 within borosilicate glass matrices is important for the development of novel matrices toward immobilization of sulfate containing high‐level nuclear wastes. Present investigation shows, within sodium barium borosilicate glass matrix V 2 O 5 can be homogeneously added up to 5 mol% and beyond which it separates out into three phases, for example, (i) silica (ii) Barium (Ba) – Vanadium (V) oxide, and (iii) glass matrix. 29 Si MAS NMR (Nuclear Magnetic Resonance) studies of the samples show that below 5 mol% V 2 O 5 addition, silicate network is dominantly constituted of Q 2 and Q 3 structural units, whereas above this, the network gets more polymerized through formation of Q 3 and Q 4 units. In case of borate network, 11 B MAS NMR investigations revealed that the concentration of BO 4 [(0B, 4Si)] unit increases gradually up to 5 mol% and then it decreases at the cost of BO 4 [(1B, 3Si)], BO 3 (symmetric) and BO 3 (asymmetric) units. Micro‐Raman analyses of the samples showed that with additions of V 2 O 5 in diluted concentrations, amorphous silicate network remained unaltered, whereas some amplification in signals corresponding to ring‐type metaborate and VO 5 units exists. It is therefore apparent from both MAS ‐ NMR and micro‐Raman studies that with V 2 O 5 additions within the solubility limit (≤5 mol%), borate network gets depolymerized leading to decrease in hardness from an average value of 5.0–4.2 GPa.