Influence of zirconium on the structure of pristine and leached soda-lime borosilicate glasses:: Towards a quantitative approach by 17O MQMAS NMR

O-17 MQMAS NMR was used to characterize the influence of zirconium on the structural organization of soda-lime borosilicate glasses. A new method of quantitative analysis of the O-17 MQIMAS spectra is presented, by a direct fit of the two-dimensional MQIMAS spectrum which provides the resolution of all the structural groups in glasses containing up to five oxides. Additional data were also obtained from the quantitative deconvolution of the B-11 MAS NMR spectra, with the help of the direct fit of MQMAS data as well. Excess of non-bridging oxygen is clearly identified in these glasses. Sixfolded zirconium is preferentially compensated rather than the tetrahedral boron and calcium only partially compensate the tetrahedral boron. Alteration gels arising from glass leaching were probed by oxygen-17 supplied by the alteration solution. Most of the zirconium is inserted in the silicate network forming Si-O-Zr bonds with the same configuration in the glass and in the gel. During leaching, calcium clearly remains in the alteration gel, either near non-bridging oxygen or as a zirconium charge compensator. This quantitative approach applied to O-17 MQMAS spectra demonstrates its potential for investigating the structure of increasingly complex glass and gel compositions. (C) 2008 Elsevier B.V. All rights reserved.