Abstract
Electron paramagnetic resonance (EPR) spectra of sodium–germanate glasses ( xGeO 2·(1− x)Na 2O, 0.65< x<1) prepared by the conventional melting technique are analyzed as a function of the Na 2O content, before and after X-ray irradiation. Signals due to three-fold coordinated Ge sites (Ge E ′ centers) and non-bridging oxygen hole centers (NBOHCs) are observed, whereas no signal due to paramagnetic centers related to GeO 6 sites is detected. At high Na 2O concentration, a broad signal at g=2.21 is also observed. The EPR results suggest three main mechanisms for the Na + ion insertion: interstitial; network modifier; a source of medium range structural rearrangements of GeO 4 tetrahedra.
Published Version
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