Evidence for 6‐Coordinated Zirconium in Inactive Nuclear Waste Glasses

Abstract

In inactive glasses used as models for French nuclear waste forms, Zr K ‐ and L 2,3 ‐edge X‐ray absorption spectroscopy spectra indicate that Zr is only 6‐coordinated, with d (Zr‐O) distances of 2.08 ± 0.01 Å and with a small radial disorder. Beyond, the first coordination shell, next‐nearest Si neighbors occur at about 3.4 Å. These distances exclude the presence of [7] Zr and/or [8] Zr and suggest [6] Zr‐O‐Si angles close to 130°, indicating corner‐shared ZrO 6 and SiO 4 polyhedra. This structural configuration is similar to those observed in some crystalline zirconosilicates and is in agreement with the stability of Zr in borosilicate melts and glasses.