EFFECT OF TEMPERATURE ON REDOX EQUILIBRIA IN PHOSPHATE-GLASSES AND MELTS

The glass Cs2O.P2O5 (1.5:1) is afairly mobile liquid at 500 degrees C and can be used for studying changes in redox equilibria as the melt t ransforms into a glass. Experimental requirements and limitations for viable spectrophotometric measurement (in the visble/ultraviolet regio n) are discussed and results of such studies for the following equilib ria are reported: (1) 4Cr(6+)+6O(2-) = 4Cr(3+)+3O(2) and (2) Cr6++3Ce( 3+) = Cr3++3Ce(4+). The spectral changes that occur as the melt slowly cools from 500 degrees C indicate displacement to the right hand side for both equilibria, with no disruption through T-g.