Verification of the " Tg-A Rule" in Potassium Silicate and Sodium Tungstate Glasses *

A linear relationship exists in oxide glasses between glass transition temperature (Tg) and quadrupole splitting ( A ) of Fe , + . DTA and Mössbauer measurements of silicate and tungstate glasses yielded large slopes of 680 and 260 °C/(mm s~ 1 ) f rom the slope of the straight lines when Fe + occupied, as network former (NWF), distorted tetrahedral Si and distorted octahedral W 6 + sites, respectively. This linear relationship, named a 'T g -Z \ rule", suggests that Fe is in proportion to the distortion of NWF-oxygen polyhedra and a higher activation energy is required for the f ragments of glass to have a cooperative movement in the supercooled liquid state. The rule" was also valid in the case of potassium silicate glasses heat treated at the temperature close to 7g, indicating a distortion of S i 0 4 and F e 0 4 tetrahedra. Substitution of Fe + for individual N W F in silicate and tungstate glasses was confirmed f rom the Fourier t ransform infrared (FT-IR) spectra because only the absorption bands due to Si and W were respectively observed without the bands due to Fe.