Nitrogen-Containing Paramagnetic Centers in Vitreous Silica

The results of a study on the structure and spectral characteristics of nitrogen-containing paramagnetic defects in vitreous silicas are presented. The UV irradiation, γ-irradiation, and mechanical destruction of nitrogen-doped vitreous silicas, which were synthesized using a plasma-chemical SPCVD technology, were used for the generation of paramagnetic centers. Another technique for producing nitrogen-containing paramagnetic centers was the target-oriented chemical modification of the surface defects of silica with the use of NH₃ (ND₃) molecules. Paramagnetic centers with free valences at silicon (≡Si-O-)₂Si^· (-NH₂) and (≡Si-O-)₂Si^· -N(-Si≡)₂] and nitrogen atoms ≡Si-N^· -H and ≡Si-N^· -Si≡] were detected. The reactivity of nitrogen-centered radicals toward H₂ and CO molecules was studied. Quantum-chemical calculations of model systems were employed in the interpretation of the experimental data. The strengths of Si-O and Si-N bonds in vitreous silica were compared.__________Translated from Kinetika i Kataliz, Vol. 46, No. 4, 2005, pp. 615–634.Original Russian Text Copyright © 2005 by Radtsig.