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Fining Behavior in Alkaline Earth Aluminoborosilicate Melts Doped with As2O5 and SnO2


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In this work the gas evolution behavior and the fining ability of the alkali-free alkaline earth aluminoborosilicate glass batches doped with As2O5 or SnO2 were examined, and the redox behavior of As and Sn ion in the corresponding fined melts was investigated by square wave voltammetry. The evolved gas analysis showed a distinct difference at begin temperature of O2 emission and in evolved O2 volume between glass batches doped with As2O5 and SnO2. One peak due to reduction of As5+ to As3+ or Sn4+ to Sn2+ was shown in the voltammograms. Glass batch doped with SnO2 showed better fining in the first fining zone, but batch doped with As2O5 is more excellent in the overall fining inclusive of the second fining. This difference in fining behavior was discussed by combination of O2 evolution from batches and redox ratio in melts. Finally, it was suggested that the earlier oxidation of As ion in the second fining zone contributed to the excellent fining of melts.