Strutural Relaxation of Semiconducting Vanadate and IR-Transmitting Gallate Glasses Containing Iron

Glass transition temperature (T g ) is proportional to the quadrupole splitting (Δ) of Fe(Ⅲ) obtained from the 57 Fe Mossbauer spectra ('T g ?Δ rules' (1990)). The values of Δ reflect the distortion of Fe(Ⅲ) atoms, which occupy the sites of network-forming atoms. Heat treatment of potassium vanadate and calcium gallate glasses at around the individual T g causes a structural relaxation, accompanying a linear decrease of T g and Δ values. These experimental results prove that T g decreases with a decrease in the distortion of VO₄, GaO₄, and FeO₄ tetrahedra, as the 'T g ?Δ rule' predicted.