Equilibrium concentration of oxygen rich and deficient defect centers in germanosilicate glasses

Equilibrium concentrations of oxygen rich and deficient defect centers are calculated as a function of temperature and glass redox condition for germanosilicate glasses. We have here used the approach of Silin and Lace [J. Non-Cryst. Solids 149 (1992) 54-61] but extended it to include the case of binary system of germanosilicate glasses. A set of 23 reactions is identified as the possible pathway for formation of different defect centers. Each of these reactions are represented by forward and backward steps with Arrhenius kinetics and their activation energies are estimated based on the relevant bond energies of the involved species. Equilibrium concentrations are determined by setting rates of each of these reactions equal to zero. Typical results are presented for glasses which are: (i) stoichiometric, (ii) glasses with excess oxygen levels of 10¹⁶ to 10²⁰ cm⁻³, and (iii) glasses which are oxygen deficient by 10¹⁶ to 10¹⁸ cm⁻³.