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'Chemical exchange' in keywords
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2000 (1)
1992 (1)
1Author    Hiroshi Ohki, Nobuo NakamuraRequires cookie*
 Title    Sodium Ion Exchange in Na 1+x Zr 2 Si x P 3 _ ;c 0 1 2 as Studied by 23 Na Nutation NMR  
 Abstract    23 Na two-dimensional nutation NMR was applied to Nat + *Zr2SivP3_vO,2 with x = 0, 1, and 2. The nutation spectrum in each compound consists of two clearly separated peaks corresponding to the two crystallographically inequivalent sodium sites. In the compound with x = 2 the nuclear quadrupole coupling constants (e Qq/h) and the asymmetry parameters (rj) were by spectral simu-lation estimated to be 1.0 MHz and 0 for one site, and 1.5 MHz and 0.8 for the other site. The spectrum varies considerably on heating; the two peaks merge into a single peak at high tempera-tures due to fast ion exchange between the two different sites. For x = 0 and x = 1 the nutation spectra did not show any significant temperature dependence, suggesting that the rates of the sodium ion exchange are negligibly low. 
  Reference    Z. Naturforsch. 47a, 319—324 (1992); received August 10 1991 
  Published    1992 
  Keywords    Nutation NMR, Quadrupole effect, Superionic conductor, Chemical exchange 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0319.pdf 
 Identifier    ZNA-1992-47a-0319 
 Volume    47 
2Author    Hirotsugu Masui, Takahiro Ueda, Keisuke Miyakubo, Taro Eguchi, Nobuo NakamuraRequires cookie*
 Title    Na NMR Study of NASICON-type Compounds, Na 1+x Sc x Ti 2 x (P0 4 ) 3  
 Abstract    The structure of NASICON-type compounds, Nai +x Sc x Ti 2 _z(P0 4)3 (0 < x < 2), and the dynamics of Na + have been investigated by 23 Na NMR spectroscopy. It was found that the 23 Na ID and 2D MQMAS spectra depend on the Na concentration, suggesting strongly that the Na + ions are distributed between two crystallographically nonequivalent sites, one is a special position with axial symmetry, and the other a position of low symmetry. The chemical exchange between these different sites in the crystal takes place at room temperature, which may cause the high Na ion conduction of this material. 
  Reference    Z. Naturforsch. 55a, 348—352 (2000); received August 30 1999 
  Published    2000 
  Keywords    NASICON, Superionic Conductor, 2D MQMAS NMR, Chemical Exchange 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0348.pdf 
 Identifier    ZNA-2000-55a-0348 
 Volume    55