NMR Study of a Rare-Earth Aluminoborosilicate Glass with Varying CaO-to-Na2O Ratio

• DOI: 10.1007/s00723-007-0041-0
• Publication Date: 2008-04-10T00:11:58Z
• Authors: A. Quintas; T. Charpentier; O. Majérus; D. Caurant; J.-L. Dussossoy; P. Vermaut
• Keywords: 0103 physical sciences; 01 natural sciences

The effect of substituting two Na+ by one Ca2+ in a rare-earth aluminoborosilicate glass is investigated by multinuclear magic-angle spinning (MAS) and multiple-quantum (MQ)MAS nuclear magnetic resonance (NMR) spectroscopy. Quantitative analysis of the 23Na and 27Al MAS/MQMAS data along with the 11B MAS NMR data provides complementary information enabling to cast light on different structural key points. A strong decrease of the N4 = BO4/(BO3 + BO4) ratio is observed consecutively to this substitution, indicating that sodium is more favorable than calcium to the formation of BO4 units. The experimental N4 ratio is compared to the Dell and Bray model prediction and it is shown that several adjustments, due to the presence in our glass of Nd and Zr, are necessary to obtain acceptable agreement with experimental data. 29Si MAS NMR data also put in evidence an effect of the substitution on the polymerization degree. Glass in glass phase separation is clearly detected when the ratio of CaO to Na2O is greater than 1 and a different evolution of NMR parameters is observed for the ratio of CaO to Na2O being less than or equal to 1. Concerning aluminum charge compensation, it is demonstrated that, as long as no phase separation is detected, the negative charge of AlO4− entities is almost exclusively balanced by sodium cations. Finally, changes of the sodium ions organization within the glass network are also evidenced by spin–lattice relaxation and spin echo decay measurements.