Separation of a Composite Internal Friction Peak of 24.8Li₂O⋅1.3MgO⋅73.9SiO₂ Glass

Abstract

Internal friction of 16.3Na₂O⋅33.7MgO⋅50.0SiO₂ and 24.8Li₂O⋅1.3MgO⋅73.9SiO₂ glasses was measured with an inverted torsion pendulum at frequencies below 1Hz. The gamma distribution function was the most appropriate for approximating the whole shape of the low- and high-temperature peak which appeared separately in the internal friction curve of 16.3Na₂O⋅33.7MgO⋅50.0SiO₂ glass among the tested distribution functions: lognormal, beta and gamma. The intermediate- and high-temperature peaks were separated from the composite peaks observed in the internal friction curves of 24.8Li₂O⋅1.3MgO⋅73.9SiO₂ glass by approximating those peaks with the gamma distribution function and the activation energies for those peaks were determined. The activation energies for oxygen and magnesium diffusion below the glass transition point in the 24.8Li₂O⋅1.3MgO⋅73.9SiO₂ glass were also determined by use of stable isotopes ¹⁸O and ²⁶Mg, respectively. Within experimental errors, the activation energies for the intermediate- and high-temperature peak agreed with those for oxygen and magnesium diffusion, respectively.