The influence of oxide additions on the oxidation states of polyvalent dopants in ZBLAN glasses

The effect of ZrO2 additions on the oxidation states of the polyvalent elements Fe, Cu, Cr, In and Eu in ZBLAN glasses have been investigated. 0-1 mol% Zr02 was added to ZBLAN glasses containing 0.5 mol% of the dopant elements and the glasses were processed under inert atmosphere in a vitreous carbon crucible. The oxidation states of the various dopants were examined by optical absorption spectroscopy of the glasses, and the oxygen content was determined using the LECO combustion method. Oxide additions were found to markedly reduce the oxidation state of the investigated dopants in the ZBLAN glasses. The reduction of iron and copper were studied most thoroughly and a positive correlation between the fraction of the dopant metals reduced and increasing ZrO 2 additions were found. Possible reactions in the melt are discussed and related to previous work on the oxidation states of these elements in ZBLAN glasses.