|Title||Solid-state NMR characterization of the mineral searlesite and its detection in complex synthesis mixtures|
|Publication Type||Journal Article|
|Year of Publication||2001|
|Authors||Fyfe, CA, Skibsted, J, Schwieger, W|
|Type of Article||Article|
|Keywords||BORATE, BORON, ISOMORPHOUS SUBSTITUTION, LAYERED SILICATES, MAGADIITE, MAS NMR, QUADRUPOLAR NUCLEI, SATELLITE, SILICON, TRANSITIONS|
The mineral searlesite (NaBSi2O5(OH)(2)) was synthesized and characterized by H-1, B-11, Na-23, and Si-29 magic-angle spinning (MAS) NMR spectroscopy. From these spectra, the B-11 and Na-23 quadrupole coupling parameters and isotropic chemical shifts and the Si-29 chemical shift anisotropies have been precisely determined. These parameters are all consistent with the local environments obtained from the crystal structure for searlesite from X-ray diffraction, and they demonstrate that the synthetic sample has a high degree of both short- and long-range order. Furthermore, these anisotropic parameters are found to provide a unique fingerprinting of searlesite in complex mixtures where the presence of this mineral is not anticipated. This is demonstrated for product mixtures formed in attempts to incorporate boron in the structures of the layer silicates magadiite and kenyaite. These. mixtures have been investigated by B-11, Na-23, and Si-29 MAS NMR which clearly reveal that the samples are mixtures of searlesite and magadiite/kenyaite and that searlesite production consumes all of the boron in these synthesis mixtures. However, the Si-29 MAS NMR spectra of these mixtures indicate that the presence of boron in the reaction mixtures nevertheless has an important influence on the quality of the magadiite and kenyaite layer silicates produced.
|URL||<Go to ISI>://000171932500026|