Dynamic properties of zinc halide glasses and melts

S.N. Yannopoulos, E.A. Pavlatou

Chimica Chronica-New Series (1994), 23, 257-263

Photon correlation and Brillouin spectroscopy have been applied in the glass forming systems ZnCl2, ZnBr2 and the 50% ZnCl2-ZnBrmixture, in order to study the dynamics of local density fluctuations below Tg and far above Tm. The density correlation function of pure ZnCl2 near Tg is well represend by the non-exponential form exp(-t/τ)β with β=0.706±0.012 insensitive to temperature. The high value of β parameter categorizes ZnCl2 in the class of relative "strong" glasses with an Arrhenius temperature dependence of relaxation time τ near Tg (Tg+80°C). The hypersonic properties of pure components and the 50% mixture were also studied in the GHz region, where a single relaxation process was revealed (β=1). The limiting sound velocities uo and u∞ were calculated, showing up a linear decrease with temperature. The longitudinal relaxation time τi was found to follow an Arrhenius type relation.

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