Free volume fragmentation in glassy chalcogenides during natural physical ageing as probed by PAL spectroscopy

Free volume redistribution, caused by structural relaxation during long-term natural physical ageing, is revealed by positron annihilation lifetime technique for AsxSe100-x and GeySe100-y glasses. It is shown, that two-state positron trapping model is appropriate for an adequate description of changes caused by long-term physical ageing in the atomic-deficient subsystem of these materials. The observed behaviour of defect-related component in the fit of the experimentally measured PAL spectra for aged and rejuvenated glasses testifies in favour of fragmentation of larger free volume entities.