Structure and properties of ion-exchanged Na2O-Cu2O-Al2O3-SiO2 glass system

The structure and properties of an ion exchanged sample in the Na2O-Cu2O-Al2O3-SiO2 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(2)O . 10Al(2)O(3) . 70SiO(2) (mol%) in composition was subjected to the ion exchange in a molten CuCl-CuI salt mixture, under an N-2 atmosphere within a glove box at 400 degrees 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 degrees C. The thermal expansion coefficient and electric conductivity of the ion exchanged sample were 32.2 x 10(-7)degrees C-1, 1.3 x 10(-4) S cm(-1) at 200 degrees 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. (C) 1997 Elsevier Science B.V.