X-ray absorption studies of the local environment of Zr in high-zirconia borosilicate glasses

• Published in: Journal of non-crystalline solids Vol. 258; no. 1; pp. 98 - 109
• Main Authors: McKeown, David A., Muller, Isabelle S., Buechele, Andrew C., Pegg, Ian L.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.11.1999; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Disordered solids; Exact sciences and technology; Glasses; Physics; Structure of solids and liquids; crystallography; 61.10.Lx; E330; 61.43.Fs; Z100; Local structure; Coordination number; XANES; Radial distribution function; Multiple system; Composition effect; X-ray spectra; Glass structure; Experimental study; Borosilicate glass; EXAFS; Synchrotron radiation
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/S0022-3093(99)00517-7

Zirconium X-ray absorption spectroscopic (XAS) data were collected and analyzed for a series of zirconia borosilicate glasses developed as potential formulations for immobilization of nuclear fuel reprocessing wastes. For the first time, XAS are presented for silicate glasses with zirconia concentrations as high as 21 wt% and for zektzerite (LiNaZrSi 6O 15), a crystalline standard that is chemically similar to the glasses. Two other glass series were investigated where the CaO and ZnO contents were varied individually, while the Zr content was held constant. The analysis results indicate that Zr 4+ is predominantly in octahedral sites in the glasses. Trends in the data also show that the Zr environments in the glasses are sensitive to changes in ZrO 2 concentration, but are less sensitive to changes in Zn or Ca content. With addition of zirconia, the Zr site population shifts from mostly six-coordinated with minor amounts of seven-coordinated Zr, to having a larger fraction of seven-coordinated Zr sites, while maintaining a majority of octahedral Zr. The seven-coordinated Zr atoms probably act as nucleation sites in the glass; as the zirconia content increases to 15 wt% and higher, the numbers of these sites become large enough to promote ZrO 2 baddeleyite crystallization. There is no evidence of Zr–Zr pair correlations, similar to those observed in baddeleyite, in any of the crystal-free glasses.