Mechanism of selenium pink colouration in glass

Abstract

The mechanism of pink colouration with selenium in glass has been studied. When selenium-containing glasses are melted under reducing conditions, loss of selenium from the melt is decreased but a dark brown colour results due to the iron-selenide-oxide complex formation. Even a small amount of CeO₂ in the batch oxidizes selenium and bleaches the pink colour; large concentrations of arsenic oxide in the batch also have the same effect. Oxidizing conditions in the melt do not produce any larger selenium loss from the melt than that with “neutral” melting conditions. On electron microscope examination, pink glasses coloured with selenium revealed spherical particles. Mie's scattering curves due to spherical selenium particles of different average sizes and size distributions have been calculated and the experimental absorption bands of pink selenium glasses have been shown to be consistent with elemental selenium particles of average diameter 50 to 250 nm with large size distributions.