Effect of batch melting temperature and raw material on iron redox state in sodium silicate glasses

In this study, the redox state of iron in sodium silicate glasses was varied by changing the melting conditions, such as the melting temperature and particle size of iron oxide. The oxidation states of the iron ion were determined by wet chemical anal-ysis and UV–Vis spectroscopy methods. Iron commonly exists as an equilibrium mixture of ferrous ions, Fe2+, and ferric ions Fe3+. In this study, sodium silicate glasses containing nanoparticles of iron oxide (0.5 % mol) were prepared at various temperatures. Increase of temperature led to the transformation of ferric ions to ferrous ions, and the intensity of the ferrous peak in 1050 nm increased. Nanoparticle iron oxide caused fewer ferrous ions to be formed and the equilibrium ratio compared to that with micro-oxide iron powder was lower