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'Neutron scattering' in keywords Facet   Publication Year 2001  [X]
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2001[X]
1Author    Uwe Hoppe, Rainer Kranold, Emil Gattefa, Jörg Neuefeindb, DavidA. KeencRequires cookie*
 Title    An X-ray and Neutron Scattering Study of the Structure of Zinc Vanadate Glasses  
 Abstract    The short-range order of vitreous V20 5 and of three (Zn0)Jt(V20 5)1_x glasses with x = 0.2, 0.4, and 0.5 is studied by X-ray and neutron diffraction experiments where the change of the contrast allows to resolve the V -0 and Z n -0 correlations. The V -0 and the Z n -0 first-neighbor peaks are approximat­ ed by several Gaussian functions. In case of vitreous V20 5 two obvious V -0 distances exist which are related with V 0 4 and V 0 5 units. With ZnO additions the V -O coordination number decreases from 4.4 in vitreous V20 5 to 4.0 in the metavanadate glass where the strongest decrease of the fraction of V 0 5 units is found for glasses of * < 0.2. Dominantly, the V 0 5 groups are linked with the neighboring units by comers. The Z n-0 coordination numbers of the modified glasses are about five with closest dis­ tances of = 0.200 nm. 
  Reference    Z. Naturforsch. 56a, 478—4 (2001); received April 3 2001 
  Published    2001 
  Keywords    Neutron Scattering, X-ray Scattering, Short-range Order, Vanadate Glasses 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0478.pdf 
 Identifier    ZNA-2001-56a-0478 
 Volume    56 
2Author    Z. NaturforschRequires cookie*
 Title    A Neutron and X-ray Diffraction Study of the Structure of Nd Phosphate Glasses  
 Abstract    Diffraction experiments were performed on two (Nd203)x(P205)i_ x glasses for studying the en­ vironmental order of the Nd3+ cations. In case of the metaphosphate glass (x = 0.25) a combination of X-ray and neutron diffraction data was used to separate the N d-0 and 0 -0 first neighbor peaks. An N d-0 coordination number of 6.6±0.3 and a mean N d-0 distance of (0.239±0.001) nm were determined. In the ultraphosphate glass studied (x = 0.20) these values increase to 6.9±0.3 and (0.240±0.001) nm where the N d-0 coordination number is equal to the number of terminal oxygen atoms (0 T) which are available for coordination of each Nd3+ cation. This indicates the formation of NdOn polyhedra not sharing any O atom where also all 0 T's are in N d-0T-P positions. In the metaphosphate glass the NdO" polyhedra have to share some 0 T sites. 
  Reference    Z. Naturforsch. 56a, 237—243 (2001); received January 8 2001 
  Published    2001 
  Keywords    Neutron Scattering, X-ray Scattering, Short-range Order, Phosphate Glasses 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0237.pdf 
 Identifier    ZNA-2001-56a-0237 
 Volume    56 
3Author    E. Mikuli, A. Migdał-Mikuli, I. Natkanieca, B. GradRequires cookie*
 Title    Phase Transitions and Water Dynamics of [Co(H20 ) 6](C104)2 and [Mn(H20 ) 6](BF4)2 Studied by Neutron Scattering Methods  
 Abstract    Inelastic incoherent neutron scattering (IINS) spectra and neutron powder diffraction (NPD) patterns, registered for [Co(H20) 6](C104)2 at 18 -270 K and for [Mn(H20) 6](BF4)2 at 18 -230 K, provided evidence that these crystals possess three solid phases in these ranges of temperatures. In both compounds the phase transition occurring at T C3 is connected with a change of the crystal structure, and that occurring at T C2 with a change in the rate of the reorientational motions of H20 ligands. 
  Reference    Z. Naturforsch. 56a, 244 (2001); received December 12 2000 
  Published    2001 
  Keywords    Hexaaquacobalt(II) chlorate(VII) and Hexaaquamanganese(II) tetrafluoroborate, Phase Transitions, Structural Changes, Water Reorientation, Neutron Scattering 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0244.pdf 
 Identifier    ZNA-2001-56a-0244 
 Volume    56 
4Author    P. Andonov, H. E. Fischer3 ', P. Palleau3, S. KimurabRequires cookie*
 Title    Structural Study of Liquid Lithium Niobate by Neutron Diffraction Role of the Li Atom in the Clustering Near Solidification  
 Abstract    The structure of liquid LiNb03 has been investigated by neutron diffraction using samples with dif­ ferent isotopic composition of lithium. The intensity scattered by these samples has been measured for momentum transfers 0.4 A-1 < Q < 17.1 Ä-1 and temperatures 1600 K>T> 1500 K, which include the undercooling domain. From an analysis of the correlation functions Gt j (r) of the atomic pairs Li-Li, Li-Nb, Li-O and their structural evolutions, given by A G,_v (r) = G,_j (r)1500 -G,_, (r)1550 made with reference to the crystalline LiNb03 ferroelectric structure, it was possible to confirm a local ordering similar to that of the crystal. The presence of clusters (groupings of N b 03 octahedra) is confirmed. Both regular and irregular N b06 octahedra are observed in the liquid near solidification. With its high mobil­ ity in the melt, the Li atom plays an important role in the clustering: the Li— O and Li— Nb bonds make possible the staking of four octahedra groups into clusters of eight octahedra or more. The Li-Li bonds join these groups. The diameter of the clusters is a least 22 A in the undercooling regime. 
  Reference    Z. Naturforsch. 56a, 395—406 (2001); received February 12 2001 
  Published    2001 
  Keywords    Structure of Liquids, Neutron Scattering, Atomic Clusters, Liquid Lithium Niobate 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0395.pdf 
 Identifier    ZNA-2001-56a-0395 
 Volume    56