Raman microprobe investigation of sulphur-doped alkali borate glasses

Coloured as well as colourless binary sodium and potassium borate glasses (20-30 mol% Na2O and 5-35 mol% K2O) doped with sulphur in various concentrations (0.3-6 wt%) were prepared by melting together the appropriate weights of sodium and potassium carbonates, boric acid and sulphur. Melting was carried out in platinum-2% rhodium crucibles in an electrically heated furnace at 1000 degrees+/-10 degrees C for 2 h. The glasses were annealed at, depending on alkali content, temperatures in the range 300-350 degrees C for 1/2 h and slowly cooled at the rate of 2 degrees C/min to room temperature to release strain. The Raman microprobe spectra of the glasses prepared were measured in the range of 200 to 1600 cm(-1) using the green line of an argon laser (514.5 nm) for Raman spectral excitation. The Raman data obtained in this study were compared with Raman spectral data of known sulphur states stable in sulphur-containing solids and solutions to identify the different states of sulphur Formed in the glasses studied. A comparison was also made with published data for similar glass compositions using other spectral techniques. The Raman data obtained were found to support and complement published results of the UV and visible absorption and Raman spectra of sulphur doped glasses of similar compositions.