HETEROGENEOUS NO3- ION DYNAMICS NEAR THE GLASS-TRANSITION IN THE FRAGILE IONIC GLASS FORMER CA0.4K0.6(NO3)(1.4) - A N-15 NMR-STUDY

The tumbling dynamics of the NO3- anions in CaO.4K0.6(NO3)(1.4) liquid have been studied close to its glass transition (T-g = 333 K) by N-15 wide line NMR spectroscopy. The time scale of this tumbling dynamics closely corresponds to that associated with the shear or ct relaxation in this material over 5 orders of magnitude. Clear evidence of bimoda l spatial heterogeneity in this dynamics was observed close to T-g wit hin a small temperature range (340 to 365 K) with the coexistence of a slow- and a fast-tumbling population of NO3- anions. The relevance of the existing models of cooperative dynamics near glass transition in explaining these observations are discussed.