High-resolution /sup 27/Al and /sup 29/Si NMR spectroscopy of glasses and crystals along the join CaMgSi/sub 2/O/sub 6/-CaAl/sub 2/SiO/sub 6/

Journal Article · · Am. Mineral.; (United States)

OSTI ID:6913792

Kirkpatrick, R J; Oestrike, R; Weiss, Jr, C A; Smith, K A; Oldfield, E

High-resolution magic-angle sample-spinning (MASS) /sup 27/Al and /sup 29/Si nuclear magnetic resonance (NMR) spectroscopic data are presented for glasses and crystals along the join CaMgSi/sub 2/O/sub 6/-CaAl/sub 2/SiO/sub 6/ (Di-Cats). For the glasses, the authors results indicate the following. (1) No /sup 27/Al NMR signal is detected for other than tetrahedrally coordinated Al, and all /sup 27/Al can be quantitatively accounted for. (2) For the glasses there is a systematic deshielding (more positive chemical shift) at Al with increasing Al content, paralleling the variation observed for crystals. (3) There is only a very small (about 2 ppm) nonsystematic variation in /sup 29/Si chemical shift cross the join. (4) The /sup 29/Si peak breadths of the glasses are much greater than for the typical crystals and become narrower with increasing Al content. (5) The observable /sup 27/Al resonances of the glasses do not change in line width with changing composition. They interpret these results as indicating that the glasses become increasingly polymerized with increasing Cats content, that Cats glass is fully polymerized, and that the lack of variation in the /sup 29/Si chemical shift is due to the opposing effects of increasing polymerization, which increases shielding, and the number of Al next-nearest neighbors, which decreases the shielding.

• Research Organization: Univ. of Illinois, Urbana
• OSTI ID: 6913792
• Journal Information: Am. Mineral.; (United States), Vol. 71:5-6
• Country of Publication: United States
• Language: English

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