Synthesis and structure refinement of a new type of layered intergrowth phase: Sb3+x Nb3−x TiO14 and Sb3+x Ta3−x TiO14

1996 ◽  
Vol 52 (6) ◽  
pp. 932-938 ◽  
Author(s):  
C. D. Ling ◽  
S. Schmid ◽  
J. G. Thompson ◽  
R. L. Withers ◽  
M. Sterns
Keyword(s):  
Electron Diffraction ◽  
Structural Characterization ◽  
Structure Refinement ◽  
Aurivillius Phase ◽  
New Type

Attempts to synthesize Sb-based analogues of the known Bi-based Aurivillius phase, Bi3TiNbO9, have led to the discovery of an isomorphous pair of a new type of layered intergrowth phase of general stoichiometry Sb3+x Nb3−x TiO14 and Sb3+x Ta3−x TiO14. Electron diffraction proved essential for the initial recognition and structural characterization of these phases. The structures of Sb3+x Nb3−x TiO14, x = 0.89, and Sb3+x Ta3−x TiO14, x = 1.26, are reported. The structures are described as ordered intergrowths of β-Sb2O4-type and Sb2O5-type structures, with NbV/TaV substituting for SbV in the former and NbV/TaV/TiIV substituting for SbV in the latter.

Structural characterization of a new type of tetranuclear metal cluster system: Pt4(PMe2Ph)4(CO)5

1969 ◽  
Vol 91 (6) ◽  
pp. 1574-1576 ◽  
Author(s):  
Robert G. Vranka ◽  
Lawrence F. Dahl ◽  
Paolo Chini ◽  
Joseph Chatt
Keyword(s):  
Structural Characterization ◽  
Metal Cluster ◽  
Cluster System ◽  
New Type

Synthesis and structural characterization of tris(2-seleno-1-mesitylimidazolyl) hydroborato complexes: A new type of strongly electron donating tripodal selenium ligand

2006 ◽  
pp. 3990 ◽  
Author(s):  
Mao Minoura ◽  
Victoria K. Landry ◽  
Jonathan G. Melnick ◽  
Keliang Pang ◽  
Luciano Marchi? ◽  
...  
Keyword(s):  
Structural Characterization ◽  
New Type

Structural characterization of polycrystalline (Nd,Al)-substituted zirconolite

2002 ◽  
Vol 757 ◽  
Author(s):  
Pascal Loiseau ◽  
Daniel Caurant ◽  
Noël Baffier ◽  
Catherine Fillet
Keyword(s):  
Structural Characterization ◽  
Single Phase ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Significant Proportion ◽  
Optical Absorption Spectroscopy ◽  
Minor Actinides ◽  
X Ray

ABSTRACTZirconolite (formally CaZrTi2O7) is a crystalline phase particularly well adapted to actinide immobilization because of its excellent long-term behavior and its good containment capacity. Most of the French studies on zirconolite deal with minor actinides that are mainly responsible for the long-term radiotoxicity of high-level radioactive wastes. For these kind of studies, trivalent minor actinides (Am3+, Cm3+) can be simulated by a lanthanide ion with an ionic radius similar to that of Nd3+. Thus, several materials having the composition Ca1-xNdxZrTi2-xAlxO7 (0 ≤ x ≤ 0.8) were prepared by solid state reaction. These polycristalline materials were first characterized by X-ray diffraction and scanning electron microscopy associated with energy dispersive X-ray analysis in order to determine the nature of the crystalline phases formed. For low neodymium content (x ≤ 0.1), electron spin resonance of Nd3+ ions revealed that a significant proportion of these ions entered into trace amounts of perovskite. Nevertheless, all Ca1-xNdxZrTi2-xAlxO7 samples with x ≤ 0.6 can be considered as almost single phase zirconolite-2M. Structure refinement by the Rietveld method of Ca0.7Nd0.3ZrTi1.7Al0.3O7 showed that Nd3+ and Al3+ ions mainly entered respectively into the calcium site and into the split five-fold coordinated titanium site. Structural characterization of Ca0.3Nd0.7ZrTi1.3Al0.7O7 and Ca0.2Nd0.8ZrTi1.2Al0.8O7 samples confirmed that these compositions led to the crystallization of almost single phase zirconolite-3O, an orthorhombic polytype of zirconolite, whose structure was also refined by the Rietveld method. Results concerning neodymium location in Ca0.7Nd0.3ZrTi1.7Al0.3O7 and Ca0.3Nd0.7ZrTi1.3Al0.7O7 were qualitatively confirmed by optical absorption spectroscopy at low temperature.

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