Structural significance of nickel sites in aluminosilicate glasses

Kado, Rikiya*; Kishi, Tetsuo*; Lelong, G.*; Galoisy, L.*; Matsumura, Daiju   ; Calas, G.*; Yano, Tetsuji*

We use Ni ions as a structural probe to investigate the influence of modifier cations on the structure of aluminosilicate glasses. The color of these glasses varies with the nature of the cations present in glass. Structural origin of this change is investigated by optical absorption and X-ray absorption spectroscopies. Our results reveal pronounced changes in Ni coordination. Tetrahedra Ni ins present in all these glasses and Ni in 5-fold coordination site also appears. There is a weak contribution from octahedral Ni. The concentration of tetrahedral Ni deduced from the optical absorption spectroscopy increases with decreasing cation field strength, explaining the variation of color from yellow and brown to purple. This is in line with X-ray absorption spectroscopy data. Cation-oxygen distances and site symmetry indicate a similar structural behavior of Mg and Ni, being a good structural probe to Mg.