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'Mixed Valence' in keywords Facet   Publication Year 1998  [X]
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1Author    Wolfgang Jeitschko, HorstA. Mons, Ute Ch, ManfredH. Rodewald, MöllerRequires cookie*
 Title    The Crystal Structure of the Potential Ferroelectric Calcium Rhenate(VI, VII) CanRe4 0 24 and its Relation to the Structure of S rn 0 s40 24  
 Abstract    The title compound was prepared in well-crystallized form by thermal decomposition of Ca5Re20i2. Its structure was determined from single-crystal X-ray diffractometer data: /4 j, a = 1107.0(1), c = 1609.3(1) pm, Z = 4, R -0.056 for 4565 structure factors and 119 variable parameters. The calcium atoms occupy seven different sites with 8, 9, or 10 oxygen neighbors. The two different rhenium atoms are octahedrally coordinated by oxygen atoms with average Re-O distances of 193.1 and 187.7 pm for the six-and seven-valent rhenium atoms, respectively. The compound shows Curie-Weiss behavior with a magnetic moment of n exp = 1.15(±0.10) Pb per Re(VI) atom. The structure is closely related to that of Srn0s4024 which, however, crystallizes in the space group I2la. The difference between the two structures arises through the higher coordination numbers of the strontium atoms. It is suggested that at high temperature both compounds crystallize in the common higher symmetry space group I4\/a. Since CanRe4024 crystallizes in the pyroelectric class 4 this compound is expected to be ferroelectric. 
  Reference    (Z. Naturforsch. 53b, 31—36 [1998]; received October 17 1997) 
  Published    1998 
  Keywords    Crystal Structure, Ferroelectrics, Mixed Valence, Rhenates, Perrhenates 
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 TEI-XML for    default:Reihe_B/53/ZNB-1998-53b-0031.pdf 
 Identifier    ZNB-1998-53b-0031 
 Volume    53