Zinc environment in aluminoborosilicate glasses by Zn K-edge extended x-ray absorption fine structure spectroscopy

The structural surrounding of Zn in inactive nuclear glasses was determined using extended x-ray absorption fine structure spectroscopy. Zn was found in tetrahedralcoordination ([4]Zn) with [4]Zn–O distances of 1.95 Å. ZnO4 tetrahedra shared corners with SiO4 tetrahedra [d(Zn–Si) around 3.20 Å]. The oxygens of the Zn–O–Si bonds were charge compensated by Na+ and, to a minor extent, by Cs+. The influence of [4]Zn on the formation of charge-compensating cations at the expense of network modifiers may explain the stabilizing effect of Zn in these glasses.