THE INFLUENCE OF OXYGEN ON THE OXIDATION-STATE OF IRON IN ZBLAN GLASSES

Although oxygen is considered an impurity in fluoride glasses, O-2 has successfully been used to oppose reduction of melts and to oxidize tr ansition metal impurities. In the present paper, the effect of minor c ontents of oxygen on the oxidation state of Fe, one of the most common impurities in ZBLAN glasses, is reported. ZrO2 was added to ZBLAN gla sses containing 0.5 mol% FeF3, and the glasses were then processed und er nitrogen atmosphere. It is shown that the oxidation state of iron h as been partly reduced to the ferrous state by this process. Possible redox reactions in the melt are discussed and related to previous stud ies.