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A high-resolution NMR study of the La-Si-Al-O-N system

Journal Article · · Journal of the American Chemical Society; (USA)
DOI:https://doi.org/10.1021/ja00196a016· OSTI ID:6903170
; ;  [1]
  1. Univ. of Warwick, Coventry (England)
High-resolution {sup 27}Al, {sup 29}Si, and {sup 139}La NMR spectra have been obtained from crystalline phases of the La-Si-Al-O-N system. These results have further defined the {sup 29}Si chemical shift ranges in mixed coordination tetrahedra (i.e., SiO{sub x}N{sub 4{minus}x}, 0 {le} x {le} 4) and enabled the cation's influence on the chemical shift in such units to be investigated for the first time. The ability to distinguish distinct local environments, despite overlap of the {sup 29}Si chemical shift ranges from different units, has allowed structural refine of certain phases (e.g., La{sub 4}Si{sub 2}O{sub 7}N{sub 2}). The {sup 27}Al NMR spectrum of LaAlO{sub 3} shows appreciable intensity from transitions other than the 1/2 {leftrightarrow} {minus}1/2, emphasizing the difficulties of quantitatively interpreting NMR spectra of quadrupole nuclei. For the first MAS is applied to {sup 139}La NMR and is shown to have some limited applicability to the study of ceramics. High-resolution multinuclear NMR is shown to be a powerful monitor of phase development and probe of compositional detail in complex ceramic phase mixtures.
OSTI ID:
6903170
Journal Information:
Journal of the American Chemical Society; (USA), Journal Name: Journal of the American Chemical Society; (USA) Vol. 111:14; ISSN 0002-7863; ISSN JACSA
Country of Publication:
United States
Language:
English