Mixed-alkali effect in sodium–potassium glasses irradiated with electrons

Irradiation induced densification and its correlation with three-membered rings in vitreous silica

“…Starting the irradiation (lower dose), local glass structure is being shrunk and the rate of compaction is very high. Larger doses seemed to cause some expansion (as for alkali-silicate glass), but this effect can be fully attributed to the increase of the contamination layer, which is significant for the long exposure times [14]. Actually, after the subtraction of the thickness of the contamination layer it is obvious that the volume expansion is but apparent and only compaction occurs, see Fig.…”

“…The rate of the contamination thickness was determined during the long-term expositions using SEM [14] and was set to 0.02 nm/s. Although AFM has an excellent vertical resolution, the precise determination of the depth of the pit depends strongly on the smoothness of the scanned profile as well as glass surface.…”

“…shifts of the equilibrium positions of atoms) [3]. Previous experiments [14][15][16] showed the response of the vitreous silica to the electron irradiation leads either to densification or to volume expansion, depending on the OH content. The volume compaction was explained as follows: incoming electrons deliver the energy to the glass structure via elastic scattering between electrons and atoms.…”

“…Some previous papers documented the volume changes in various types of glasses caused by electron irradiation of various doses [3,[12][13][14]. The glass is very sensitive to the irradiation, partially because the glass state is not in the thermodynamic ground state.…”

Changes of structure in potassium depleted binary silicate glass studied by MD

“…The rate of compression as well as the maximum shrinkage of the irradiated volume was composition dependent. The compression is attributed partially to the shrinkage of silica network (decrease of Si-O-Si angles) and partially to the spatial relaxation of around the formerly alkali sites after the alkali ions had migrated away [9]. After some time of electron irradiation the irradiated glass is fully depleted of alkali atoms but non-bridging oxygen atoms (NBO), originally bonded to alkali ions remain in the structure.…”