CHARACTER, MECHANISM OF FORMATION AND TRANSFORMATION OF POINT-DEFECTSIN TYPE-IV SILICA GLASS

In the temperature range 600-650-degrees-C, transformations of defects in quartz glass are observed. The dependence of a band at 163 nm on a nnealing temperature is measured. Changes of structure in this tempera ture range are observed for the = Si-H and =Si-OH centers. These are c aused by the appearence of a structural relaxating process at approxim ately 675-degrees-C, the character of which is not determined. It is s hown that the band at 163 nm is caused by three-coordinated non-parama gnetic silicon Si3+(T3+ center). The band at 248 nm is attributed to a n oxygen vacancy =Si-Si=. It is shown that at temperature < 650-degree s-C the formation of Si-H centers (absorption band at 2254 cm-1) is du e to the interaction of H2 with oxygen vacancies. At temperatures > 65 0-degrees-C, the interaction of H2 with T3+ centers was achieved. The maximum of the band of the =Si-H centers thus formed is at 2264 cm-1. It was assumed that, in the type IV glass, the formation of Si-OH is d ue to an interaction of H-2 with peroxy linkages. Changes of the funda mental absorption edge are correlated with the changes of concentratio n of OH groups from 1500 ppm to 2 ppm. In the region < 2 ppm, the line ar dependence of these changes on OH concentration is violated.