DECOMPOSITION AND PHASE-SEPARATION OF AGI-DOPED SILVER BORATE GLASSES

Glasses of composition (AgI)x(Ag2OB2O3)1-x (0.6 < x < 0.78) have been studied with Ag-109 NMR and differential scanning calorimetry. By progressively increasing the annealing temperature, in all our fast quenched glasses we observe separation of crystalline silver iodide followed by decomposition of Ag2O of the borate network. In most samples, this network crystallizes, and this causes the disappearance or weakening of the jump of heat capacity at the glass transition, On the other hand, in the x = 0.75 glass, moderate amounts of AgI have been crystallized and two distinct vitreous phases have been observed. The complex process of formation and growth of the crystalline AgI domain is discussed in detail for the x = 0. 7 8 sample.