Effect of thermal history on helium diffusion and solubility in vitreous B2O3 and sodium borate glasses

Abstract

Helium diffusivity and solubility in vitreous B₂O₃ and sodium borate glasses (0–7 mol% Na₂O) can be decreased by as much as 30% by thermal annealing. It is concluded that this decrease is due to thermally induced volume relaxation. Since these measurements can be made while the sample is being annealed, they can be used to determine the time dependence of the volume relaxation process. The relaxation time at 182°C for vitreous B₂O₃ as determined from the time dependence of the helium diffusion coefficient is approximately 6 × 10⁴ sec.