ИСТИНА

The As-Se glass-forming system is widely used as photosensitive materials, vidicons, optical fibers and others. However, many questions regarding their structure and relaxation features have still not been identified. An analysis of the processes occurring in the glass at its vitrification and annealing processes carried out based on the concept of nanoheteromorphous structure of multi-component glass and its special case - the concept of polymeric-polymorphoid structure of glass and glass-forming liquid of individual chemical substances (ICS). The glass is a copolymer of crystal lattice structure fragments of different polymorphic modifications (PMs) - polymorphoids - with no translational symmetry (long-range order) but with short- and intermediate-range orders of these PMs. We introduced a new Tw-rev - temperature of polymorphoids interconversion reverse of high-temperature and low-temperature PMs (HTPM and LTPM) instead of Tg that improperly replaced Tamman’s Tw (temperature of bend on the curve "property-temperature"). The regularities of ICS structure changes upon relaxation from a liquid to a solid glassy state were identified. The process of the LTPM into the HTPM polymorphoids transformation (LTPM→HTPM) occurs above the Tw-rev temperature, on the cooling melt. Below the Tw-rev temperature is the HTPM → LTPM reverse process. The paper discusses the structure and relaxation of such ICSs as As40Se60 and As50Se50, as well as their intermediate compounds, including the area without polymorphoid compositions. The photostructural transformations were analyzed in vitreous As40Se60 and As50Se50. It showed that their physical and chemical nature were directly related to the interconversion of the HTPM and LTPM polymorphoids. The glass aging mechanism is a process of the HTPM into LTPM polymorphoids transformation. The aging process does not take place in absence of polymorphoids.