29SI AND 27AI MAS-NMR SPECTROSCOPY OF β-EUCRYPTITE (LIALSIO4): THE ENTHALPY OF SI,AL ORDERING
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dc.contributor.author | Phillips B.L. | |
dc.contributor.author | Hongwu X.U. | |
dc.contributor.author | Navrotsky A. | |
dc.contributor.author | Heaney P.J. | |
dc.date.accessioned | 2021-02-03T02:20:26Z | |
dc.date.available | 2021-02-03T02:20:26Z | |
dc.date.issued | 2000 | |
dc.identifier | https://elibrary.ru/item.asp?id=31920050 | |
dc.identifier.citation | American Mineralogist, 2000, 85, 1, 181-188 | |
dc.identifier.issn | 0003-004X | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/24472 | |
dc.description.abstract | By combining data from oxide melt solution calorimetry and 29Si MAS-NMR spectroscopy, the enthalpy for short-range Si.Al ordering in β-eucryptite (LiAlSiQ4) was determined for a series of samples prepared by glass annealing. Si.Al ordered β-eucryptite gives a single 29Si NMR peak for two unresolved crystallographic sites, but two distinct 27A1 resonances that differ in both chemical shift and quadrupolar coupling. Samples of β-eucryptite crystallized from glass contain additional 29Si NMR peaks, indicating significant levels of short-range Si, Al disorder. This disorder decreases exponentially with annealing time at 1173 K, from 0.55(±0.04) Al-O-Al linkages per formula unit after one hour to 0.05(±0.01) after 70.5 hours. The decrease in the concentration of A1-O-A1 linkages with annealing time correlates linearly with enthalpies of drop-solution in molten lead borate, giving an enthalpy of ΔHord = -26 ± 3 kJ/mol for the reaction: Al-O-Al + Si-O-Si → 2(Si-O-Al). Additional NMR results are presented for samples synthesized along the SiO2-Li AlSiO4 join (quartz to β-eucryptite). Solid solution samples with compositions 20 and 69 mol% quartz appear to have very few Al-O-Al linkages (<0.04 per formula unit). | |
dc.title | 29SI AND 27AI MAS-NMR SPECTROSCOPY OF β-EUCRYPTITE (LIALSIO4): THE ENTHALPY OF SI,AL ORDERING | |
dc.type | Статья |
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