Positron trapping defects in free-volume investigation of Ge–Ga–S–CsCl glasses

•CsCl additives in Ge–Ga–S glassy matrix lead to the agglomeration of voids.•Full crystallization of Ge–Ga–S–CsCl glasses corresponds to the formation of defect voids.•Gamma-irradiation of glass stimulates the creation of additional defects and darkening.

Evolution of free-volume positron trapping defects caused by crystallization process in (80GeS2–20Ga2S3)100−х(СsCl)x, 0 ≤ x ≤ 15 chalcogenide-chalcohalide glasses was studied by positron annihilation lifetime technique. It is established that CsCl additives in Ge–Ga–S glassy matrix transform defect-related component spectra, indicating that the agglomeration of free-volume voids occurs in initial and crystallized (80GeS2–20Ga2S3)100−х(СsCl)x, 0 ≤ x ≤ 10 glasses. Void fragmentation in (80GeS2–20Ga2S3)85(СsCl)15 glass can be associated with loosing of their inner structure. Full crystallization in each of these glasses corresponds to the formation of defect-related voids. These trends are confirmed by positron-positronium decomposition algorithm. It is shown, that CsCl additives result in white shift in the visible regions in transmission spectra. The γ-irradiation of 80GeS2–20Ga2S3 base glass leads to slight long-wavelength shift of the fundamental optical absorption edge and decreasing of transmission speaks in favor of possible formation of additional defects in glasses and their darkening.