Effect of fictive temperature on the optical absorption of cobalt (II) and nickel (II) in some phosphate glasses

The optical absorption of cobalt (II) in Na₂O, 4P₂O₅ melts and in H₂ONaCl mixtures has been studied at different temperatures; the equilibrium: octahedral ? tetrahedral shifted towards the right with increasing temperature in both solvents. The optical absorption of cobalt (II) and nickel (II) has been studied in a series of metaphosphate glasses: Na₂OCaOP₂O₅, and it has been shown that the equilibrium octahedral/tetrahedral ratio of these ions measured at room temperature can be correlated with the transformation temperature of these glasses. The colour of cobalt (II) or nickel (II) containing CaO·P₂O₅ glasses has been found to be significantly dependent on thermal history; the intensity of optical absorption changed reversibly on heat treatment at the transformation range of the glass.