Precise measurement of density in the isothermal relaxation processes of Pd_42.5Cu₃₀Ni_7.5P₂₀ and Zr ₅₀Cu₄₀Al₁₀ glasses

The isothermal relaxation processes of bulk Zr₅₀Cu ₄₀Al₁₀ and Pd_42.5Cu₃₀Ni _7.5P₂₀ glasses were examined by density reduction associated with relaxation. Density experiments were carried out by buoyancy method at room temperature. The isothermal relaxation curves were best fitted by a stretched exponential function with a Kohlrausch exponent less than unity. Based on free volume model, the reduced free volume x_f/^as = 0.0355 and flow defect concentrationC_f/^as= 5.80 × 10^-13 in as-quenched state was obtained for Pd_42.5Cu ₃₀Ni_7.5P₂₀ glass. However, the temperature at which the free volume started to deviate from equilibrium concentration on cooling of the melt was not in accordance with calorimetric glass transition temperature.