Raman investigation of vitreous and molten boric oxide

Abstract

Raman data have been obtained for vitreous and molten B2O3 from −196 to 1594 °C. A ΔH° of 6.4±0.4 kcal/mole boroxol was obtained from the temperature dependence of ratios of integrated Raman intensities. This heat is thought to correspond to the transformation of BO3 triangles in boroxol rings, to BO3 triangles in a random network. Vitreous B2O3 is composed predominantly of boroxol rings, but the boroxol ring concentration decreases with increasing temperature in the melt, and becomes small at temperatures above 1600 °C.