Effects of annealing of the GeO/sub 2/ glasses on their paramagnetic center concentration

Paramagnetic resonance spectra of GeO/sub 2/-glasses were measured at 9 GHz and temperatures from 100 to 300 K as a function of T/sub phi/ and annealing time. T/sub phi/, the temperature at which the glass melt was equilibrated, was chosen to be 1450, 1550, and 1650 C, and the annealing temperature was 420 C. The concentration of the E/sub 1/-center, measured in the as produced glass was least in the 1550 C glass. Paramagnetic centers were not detected in any of the samples after annealing for about 15 minutes. The E/sub 1/-and a new defect center were detected after 20-min annealing treatments. The total concentration of the paramagnetic states after 30 minutes of treatments is highest in the 1550 C glass. With further annealing the paramagnetic center concentration decreases, reaching an equilibrium value after 31 hours. The total paramagnetic defect center concentration in the glasses annealed for 31 hours before and after irradiation exhibits the same pattern with respect to T/sub phi/ as the E/sub i/-concentration dependence on T/sub phi/ obtained in the as produced GeO/sub 2/ glasses before and after irradiation, respectively. Although the defect-center concentration decreased by annealing the glasses, their structure manifested by T/sub phi/ is maintained.