EXAFS study on the local environment of Cu+ ions in glasses of the Cu2O–Na2O–Al2O3–SiO2 system prepared by Cu+/Na+ ion exchange

Abstract The local environment around Cu + in Cu + /Na + ion-exchanged sodium aluminosilicate glasses was investigated as a function of the ratio x (x= Cu + /[ Cu + + Na + ]) by extended X-ray absorption fine structure spectroscopy (EXAFS). Glass specimens with various ratios were prepared by ion exchange in 20Na 2 O–10Al 2 O 3 –70SiO 2 (mol%) glass at 400°C followed by concentration equalizing treatment. The coordination number N of Cu + in the glasses of x 20Cu 2 O–(1− x )20Na 2 O–10Al 2 O 3 –70SiO 2 (mol%) increased accompanying the increase of the interatomic distance r Cu–O with increasing x: N=2.2, 2.8 and 3.7, and r Cu – O =0.184, 0.188 and 0.191 nm for the samples of x=0.2, 0.4 and 0.63, respectively. The change in the coordination of Cu + was discussed in relation to the structural evolution caused by ion exchange. These changes seem to induce a change in the environment around Cu + from twofold to fourfold coordination structure. The fourfold site for Cu + offered a favorable situation for ionic conduction, because these highly ion-exchanged glass samples showed high electrical conductivity.