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1995 (1)
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1Author    H. D. Lutz, J. Himmrich, H. HaeuselerRequires cookie*
 Title    Lattice Vibration Spectra. LX. Lattice Dynamical Calculations on Spinel Type MCr 2 S 4 (M = Mn, Fe, Cd)  
 Abstract    Lattice dynamical calculations of the spinel type MCr 2 S 4 (M = Mn, Fe, Cd) have been done using various potential models (short-range, rigid-ion, polarizable-ion). The main results are that (i) the vibrational modes (eigenvectors) and potential energy distributions of the Raman and IR allowed phonon modes of the three chromium sulfides are very similar, (ii) the A-X and B-X short-range force constants (referring to AB 2 X 4) strongly depend on the structural parameter u, i.e., the tetrahedral A-X force constants are smaller than the respective octahedral B-X ones opposite to previous calculations on the basis of an ideal spinel structure with u = 0.25, (iii) bending force constants (X-A-X and X-B-X), but not X-X and B-B repulsive forces, are negligible, (iv) in the case of the breathing mode of the tetrahedral AX 4 unit (species A lg) the demand on B-X and X-X (stretching and repulsion) forces is larger than that on the A-X force, and (v) the effective dynamic charges of the bivalent metal ions are nearly zero. 
  Reference    Z. Naturforsch. 45a, 893—902 (1990); received April 9 1990 
  Published    1990 
  Keywords    Chromium sulfides, Spinels, Lattice dynamics, Force constant calculation, Vibrational modes 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0893.pdf 
 Identifier    ZNA-1990-45a-0893 
 Volume    45 
2Author    H. Haeuseler, A. CansizRequires cookie*
 Title    Die quaternären Systeme ZnAl2S4-ZnGa2S4, ZnAl2S4-CdAl2S4 und ZnAl2S4-ZnAl2Se4. Röntgenographische und schwingungsspektroskopisehe Untersuchungen Investigation of the Quaternary Systems ZnAl2S4-ZnGa2S4, ZnAl2S4-CdAl2S4, and ZnAl2Se4-ZnAl2Se4 by X-Ray Diffraction and Vibrational Spectroscopy  
 Abstract    The quasi-binary systems Zni_a:Cda;Al2S4, ZnAl^i-zjGao.^, and ZnAl2S4(i_a;)Se4:r have been investigated by X-ray diffraction and vibrational spectroscopy. In the spinel Z11AI2S4 up to 20% of Zn can be replaced by Cd. In the two other systems, ZnAl2S4 has no detectable homogeneity range. The thiogallate phases have much broader ranges of homogeneity. The compositions of the compounds at the phase boundary of the thiogallate phase are Zno.4Cdo.6Al2S4, ZnGao.4Alx.6S4, and ZnAl2S2.8Sei.2. At approximately 950 °C ZnAl2Se4 undergoes a reversible phase transition to a wurtzite-type structure. This phase transition is also observed for the solid solutions ZnAl2S4(i_a;)Se4a; with 1.0 > x > 0.3. The FIR spectra are discussed. 
  Reference    Z. Naturforsch. 38b, 311—316 (1983); eingegangen am 27. Oktober 1982 
  Published    1983 
  Keywords    Spinel, Thiogallate Type, Wurtzite Type, FIR Spectroscopy, Solid Solution 
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 TEI-XML for    default:Reihe_B/38/ZNB-1983-38b-0311.pdf 
 Identifier    ZNB-1983-38b-0311 
 Volume    38 
3Author    Y. Waseda, K. Shinoda, K. SugiyamaRequires cookie*
 Abstract    a tio n D is tr ib u tio n o f Z n F e 20 4 a n d C o F e 20 4 S p in e ls F r o m A n o m a lo u s X -R a y S c a tte r in g The distribution of Zn2 + and Co2 + cations in ferrite spinels has been determined by applying anomalous X-ray scattering (AXS) near the K absorption edges of Fe, Co and Zn. The energy dependence of the reflection intensities of ZnFe20 4, detected at the Fe K and Zn K absorption edges, can only be explained when all Zn2+ being allocated to the tetrahedral site formed by oxygens. On the other hand, the results for CoFe20 4 suggest that 78% of Co2+ occupy the octahedral site, and that the present CoFe20 4 sample is classified as inverse spinel, although a partial disorder is included. The usefulness of this AXS method coupled with the common Rietveld analysis was well-recognized by determining the cation distribution even in a system with next neighboring elements of the periodic table. 
  Reference    Z. Naturforsch. 50a, 1199—1204 (1995); received November 6 1995 
  Published    1995 
  Keywords    Anomalous X-ray scattering, Rietveld, Synchrotron radiation, Ferrite, Spinel, ZnFe20 4, CoFe20 4 
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 TEI-XML for    default:Reihe_A/50/ZNA-1995-50a-1199.pdf 
 Identifier    ZNA-1995-50a-1199 
 Volume    50