The Electrical and Optical Properties of Glasses of the Li₂OGeO₂ and Na₂OGeO₂ Systems

The optical absorption coefficient and dc conductivity of a series of glasses of the Li₂OGeO₂ and Na₂OGeO₂ systems are measured as a function of alkali content. The optical absorption in the glasses is analysed in terms of non‐direct transitions across an optical energy gap. It is found that the activation energy of the conductivity decreases with increase of the alkali concentration. The decrease of the activation energy corresponds to the change in the optical energy gap and it is concluded therefore that alkali additive shifts a deep donor level above the valence band which arises perhaps due to the non‐bridging oxygen.