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'Quadrupole effect' in keywords Facet   Publication Year 1992  [X]
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1992[X]
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    V. P. Tarasov, G. A. Kirakosyan, K. E. German, Acad Sei, UssrRequires cookie*
 Title    Anomalous Temperature Dependence of the "Tc Quadrupole Coupling and Disordering of Cesium Positions in CsTc0 4  
 Abstract    A "Tc and 133 Cs solid-state NMR study of polycrystalline CsTc04 at a field of 7.04 T and temperatures from 90 to 430 K revealed first-order quadrupole effects. "Tc quadrupole coupling constant, Cq, shows anomalous positive temperature coefficients and decreases from 2.0 MHz at 430 K to 0.45 MHz at 90 K. The asymmetry parameter, rj ("Tc), is zero at 430 K and at 210 K. The high-temperature minimum of rj is associated with a phase transition from orthorhombic to tetrag-onal and the second minimum reflects an orientational change of the principal axes q xx and q yy of the EFG-tensor. The 133 Cs NMR spectra are characterised by a superposition of the two powder multiplets from the first-order couplings which arise from magnetically and crystallographically nonequivalent cesium sites, Cs (1) and Cs (2); the population ratio of Cs (2) and Cs (1), p2/p1, varies from 2.0 at 120 K to 6.5 at 373 K. The nonequivalence and population changes are attributed to the temperature change of the crystal field potential in the vicinity of the cations. 
  Reference    Z. Naturforsch. 47a, 325—329 (1992); received July 26 1991 
  Published    1992 
  Keywords    Technetium, Cesium, Solid State NMR, Quadrupole Effects, Phase Transitions 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0325.pdf 
 Identifier    ZNA-1992-47a-0325 
 Volume    47