Structure and properties of ion-exchanged Na 2OCu 2OAl 2O 3SiO 2 glass system

Abstract

The structure and properties of an ion exchanged sample in the Na 2OCu 2OAl 2O 3SiO 2 system were compared with those of a melt-quenched sample of the same composition. Glasses containing the same amount of copper ion can be prepared by both melt quenching and Cu +/Na + ion exchange. A sample of 20Na 2O · 10Al 2O 3 · 70SiO 2 (mol%) in composition was subjected to the ion exchange in a molten CuClCul salt mixture, under an N 2 atmosphere within a glove box at 400°C. After ion exchange of 20 days, 75% of Na + in the initial sample was exchanged by Cu + and Tg of the initial sample decreased from 550 to 250°C. The thermal expansion coefficient and electric conductivity of the ion exchanged sample were 32.2 × 10 −7 °C −1, 1.3 × 10 −4 S cm −1 at 200°C, 1 kHz, respectively. These values are, respectively 6 and 10 4 times larger than those of the melt quenched sample. From these results, Cu +/Na + ion exchange changes the network structure of alumino silicate glass to a more open structure and exchanged Cu + is assumed to be a charge carrier.