Preparation and characterization of boron oxysulfide glasses

Abstract Stable, homogeneous x B 2 O 3 +(1− x )B 2 S 3 glasses were prepared between 0⩽ x ⩽0.80. It was not possible to prepare homogeneous, stable glasses of compositions 0.85⩽ x ⩽0.95 due to a strong exothermic enthalpy of mixing between the B 2 S 3 and B 2 O 3 phases. Raman and 11 B NMR spectroscopies, used to characterize the structure of the glasses, show that the boron oxide structures of B 2 O 3 especially the six-membered (thioboroxol) rings, quickly diminish with increasing sulfide content, whereas the corresponding sulfide structures in B 2 S 3 remain relatively intense as the oxide content is increased. Differential scanning calorimetry and density measurements, used to characterize the physical properties of the glasses, show that the physical properties of these boron oxysulfide glasses heavily favor the B 2 S 3 properties regardless of the amount of B 2 O 3 added to the system. It is hypothesized that the stability of the thioboroxol ring group relative to that of the BS 3/2 trigonal group is a possible source of this behavior. The large heat of mixing for B 2 O 3 rich glasses is associated with the formation of new mixed boron oxysulfide structures of composition BS i O 3− i where 0 i