Structural significance of nickel sites in aluminosilicate glasses

•Aluminosilicate glasses containing Ni were studied by spectroscopic techniques.•The proportion of [4]Ni2+ was quantified from optical absorption spectra.•Coordination of Ni2+ strongly depends on optical basicity or cation field strength.•Ni–O distance obtained from EXAFS was correlated with coordination number of Ni2+.•Ni2+ probes the local structure of Mg2+ in glass. We use Ni ions as a structural probe to investigate the influence of modifier cations (Na, K, Mg, Ca, and Ba) 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 Ni2+ is present in all these glasses and Ni2+ in 5-fold coordinated site also appears. There is a weak contribution from octahedral Ni2+. The concentration of tetrahedral Ni2+ deduced from the optical absorption spectroscopy increases with decreasing CFS, 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 Mg2+ and Ni2+, being a good structural probe of Mg.