EFFECTS OF EXCHANGE TEMPERATURE ON PROPERTIES IN FIELD-ASSISTED ION-EXCHANGED GLASS

In situ strain measurements were performed during field-assisted ion-exchange processes at high (380(DEGREES)C) and low temperatures (290(DEGREES)C). Results of strain measurements confirmed that the residual stress in field-assisted ion-exchanged glasses depended on the ion exchange temperature. Measured strain data indicated that structural relaxation of the parent glass occurred during the field-assisted ion exchange.;A viscoelastic model for field-assisted ion-exchanged glass was proposed based on the known residual-stress data for both singly and doubly ion-exchanged glass and on the strain data. The governing viscoelastic stress-strain equations for a field-assisted ion-exchanged glass tube were solved numerically by iterative finite-difference techniques.;The stresses in a mixed-alkali-ion layer in doubly ion-exchanged glass were dependent on the ion-exchange temperature and the ratio of the integrated flux of alkali ions in the second ion-exchange process to the one in the first ion-exchange process. It was found that the mixed-alkali-ion layer was not a thermo-rheologically simple material.