Evidence for 6-coordinated zirconium in inactive nuclear waste glasses

In inactive glasses used as models for French nuclear waste forms, Zr K- an d L-2,L-3-edge X-ray absorption spectroscopy spectra indicate that Zr is on ly 6-coordinated, with d(Zr-O) distances of 2.08 +/- 0.01 Angstrom and with a small radial disorder. Beyond, the first coordination shell, next-neares t Si neighbors occur at about 3.4 Angstrom. These distances exclude the pre sence of Zr-[7] and/or Zr-[8] and suggest Zr-[6]-O-Si angles close to 130 d egrees, indicating corner-shared ZrO6 and SiO4 polyhedra, This structural c onfiguration is similar to those observed in some crystalline zirconosilica tes and is in agreement with the stability of Zr in borosilicate melts and glasses.