High-temperature 23 Na MAS NMR data for albite; comparison to chemical-shift models

Other| October 01, 1995 High-temperature 23Na MAS NMR data for albite: Comparison to chemical-shift models Anna M. George; Anna M. George Stanford University, Department of Geological and Environmental Sciences, Stanford, CA, United States Search for other works by this author on: GSW Google Scholar Jonathan F. Stebbins Jonathan F. Stebbins Search for other works by this author on: GSW Google Scholar Author and Article Information Anna M. George Stanford University, Department of Geological and Environmental Sciences, Stanford, CA, United States Jonathan F. Stebbins Publisher: Mineralogical Society of America First Online: 02 Mar 2017 Online ISSN: 1945-3027 Print ISSN: 0003-004X Copyright © 1995 by the Mineralogical Society of America American Mineralogist (1995) 80 (9-10): 878–884. https://doi.org/10.2138/am-1995-9-1002 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Anna M. George, Jonathan F. Stebbins; High-temperature 23Na MAS NMR data for albite: Comparison to chemical-shift models. American Mineralogist 1995;; 80 (9-10): 878–884. doi: https://doi.org/10.2138/am-1995-9-1002 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Recently, correlations of 23Na chemical shifts with structural parameters such as bond length, coordination number, and bond strength in inorganic compounds have been proposed. When considering only silicate materials we have found that some of these models lead to conflicting predictions.To test the applicability of these correlations to silicates, we collected 23Na MAS NMR spectra of a pure, ordered albite (NaAlSi3O8) from 25 to 352 °C. Over this temperature range, the Na-O bond lengths increase, and the measured isotropic shifts relative to 1 M NaCl decrease linearly from −7.1 ppm at room temperature to −7.8 ppm at 352 °C. This agrees with the observed trend in silicates of increasing bond length leading to more negative values of δ but is not consistent with the bond-valence model, which predicts a change of several parts per million in the opposite direction over this temperature range.Quadrupolar coupling constants were also seen to change, decreasing linearly with temperature from 2.69 MHz at 20 °C to 2.30 MHz at 352 °C. Static spectra measured from 22 to 1020 °C yielded values consistent with this in the low-temperature range and continued to decrease linearly to 1.50 MHz at the highest temperature. The 23Na spin-lattice relaxation times (T1) were collected between 25 and 1140 °C as well. T1 decreases gradually up to about 500 °C and then drops rapidly, indicating that there is a change in the relaxation mechanism at this temperature. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.