GAS NUCLEATION IN A BORON OXYFLUORIDE GLASS BY B-11 AND F-19 NMR

Nuclear magnetic resonance (NMR) of B-11 and F-19 is used in this stud y to monitor the structural evolution with temperature of the inorgani c polymeric glass BO1.3F0.4 whose vitreous transition temperature, det ermined by differential scanning calorimetry, is T-g = 333 K. A local motion, essentially around the fluorine atoms, particularly on one kin d of the fluorine atoms, is observed below T-g. Above T-g this glass d ecomposes into a two-phase material - glass + gas; the origin of the f ormation of the gas is explained and the proportion gas/solid is follo wed when the temperature is varied.