LOGARITHMIC KINETICS OF THE AMORPHOUS-AMORPHOUS TRANSFORMATIONS IN SIO2 AND GEO2 GLASSES UNDER HIGH-PRESSURE

We have studied in situ the kinetics of the amorphous-amorphous coordi nation transformation in GeO2 glass and of the initial stage of transf ormation in vitreous SiO2 up to 9 GPa by volume vs time measurements u sing the precise strain-gauge technique. The volume vs time dependence at all pressure points was found to obey the logarithmic law, which d istinguishes the observed transformation kinetics from that of the ord inary transitions in crystals. The first evidence of anelastic behavio r was found from the quasistatic equation of state at P approximate to 6-7 GPa for SiO2 glass and at 2-3 GPa for GeO2 glass, i.e., at lower pressures than previously believed.