Viscosity of Glasses in the System As-Se, As-Se-S, As-Se-Te and As-Se-Tl

Abstract

The viscosity of glass in the system As-Se, As-Se-S, As-Se-Te and As-Se-Tl was measured by a new penetration viscometer2) at temperature ranging approximately from room temperature to 285°C. The results are shown in Fig. 1, 2, 4, 5 and 6. The density of the glass was also determfined within the same temperature range. The results of variation of viscosity with composition and temperature in the system As-Se, are summarized in Fig. 2, which show that the viscosity increases steadily at all temperatures with the As content up to 45 atomic per cent. The maximum at 45 atomic per cent As in the curves is interpreted as evidence of structural grouping in the glass corresponding to the compound As2Se3.From tine values of viscosity of the glass at different temperatures, the apparent activation energy Ep, that is, the activation energy at constant pressure was calculated. Its values are given in Fig. 10. Using the Macedo's equation3) for the viscosity of glass containing both the activation energy and the free volume, the relation between the activation energy at constant volume Ev and the composition of the glass was made clear.The effect of lowering viscosity (η) of glass in the ternary system was found as ranging in the order η(s)>η(Te)>η(Tl).