Dynamic light scattering and low-frequency Raman scattering study of ionic KNO3-Ca(NO3)2 mixtures

E.A. Pavlatou, G.N. Papatheodorou, A.K. Rizos, G. Fytas

The density correlation function, C(t), in the mixed ionic glass KNO3·Ca(NO3)2 with three different compositions between 50 and 70% at temperatures near and above the glass transition, Tg, was measured by photon correlation spectroscopy. The C(t) is well represented by non-exponential form exp(−t/τ)β with β=0.47±0.03 insensitive to temperature and composition variation in the investigated range. The relaxation time, τ, is independent of the wavevector, q, in the range (1.2–4.7) × 10−3−1 and its dependence on the composition arises mainly from the composition-dependent Tg. The relaxation time which is in agreement with recent neutron spin-echo (NSE) (time domain 2×10−11−2×10−9s) is associated with local rearrangements involving a few neighbouring ions. Information about local structure can be extracted from the low-frequency Raman spectra.

doi: 10.1016/0022-3093(91)90279-F

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