Optical Basicity Analysis of Vanadium-Bearing Silicate Glasses/Melts

The relationship between glass composition and optical basicity was studied by redox analysis of vanadium in Na2O- and CaO-based Al2O3–SiO2 glasses/melts. A total of 73 samples were equilibrated over a range of oxidizing/reducing atmospheres and temperatures, and the composition of resulting quenched glasses/melts was subsequently analyzed. Optical absorption of the glasses was also examined for color change with the glass composition and the partial oxygen atmosphere. The optical basicity of the quenched glass/melts was then calculated using the method reported in literature and examined with change in the glass composition, oxidizing/reducing atmosphere, and temperature during melting. A relationship was developed to express the ratio of the concentrations of the redox ions (V3+, V4+, and V5+) in terms of the equilibrium constant and the calculated optical basicity of the glass/melt. The trends in change in the redox ratios with the calculated optical basicity were similar in both calcium and sodium silicate melts/glasses. The V4+/V5+ equilibrium was more affected by a change in the calculated optical basicity compared with that of the V3+/V4+ in both sodium and calcium silicate series. Alumina saturation from the crucible did not affect the calculated optical basicity of the sodium silicate glasses, although there was a change in the corresponding redox ratios. The results are compared using different experimental parameters and are useful in glass production (including those for biomedical applications) and extractive metallurgy of vanadium.

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