ISSN:
0044-2313
Keywords:
UNb2O7
;
Chemical Transport
;
Crystal Structure
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Description / Table of Contents:
Chemical Transport and Structure of UNb2O7 - a New Type of MM′2O7Powdery UNb2O7 could be obtained by heating an äquimolar mixture of UO2 and Nb2O5 in an evacuated silica tube at 1 100°C. Chemical transport in a small temperature gradient with NbCl5/Cl2 as transport agent was successfully used for crystal synthesis. UNb2O7 crystallizes with orthorhombic symmetry; the lattice constants are a = 3.8012(7) Å; b = 21.170(8) Å; c = 6.440(2) Å and Z = 4. Structure determination in the space group Cmcm (nr. 63) let to R = 0.021 (Rw = 0.019). U and Nb1 have CN = 7, Nb2 has CN = 6 (5 + 1). Uranium is surrounded by oxygen like an doma-octahedron, niobium1 like an pentagonal-bipyramid and niobium2 like an distorted octahedron.
Notes:
Pulverförmige Präparate lassen sich durch Tempern des äquimolaren Gemenges aus UO2 und Nb2O5 in evakuierten Quarzglasampullen bei 1 100°C darstellen. Einkristalle sind durch chemischen Transport im geringen Temperaturgefälle (1 000°C → 990°C; Transportmittelkombination NbCl5/Cl2) zugänglich. UNb2O7 kristallisiert orthorhombisch mit den Gitterkonstanten a = 3,8012(7) Å; b = 21,170(8) Å; c = 6,440(2) Å und Z = 4. Die Strukturaufklärung in der Raumgruppe Cmcm (Nr. 63), die bei R = 0,021 (Rw = 0,019) konvergierte, ergab für U und Nb1 CN = 7, für Nb2 CN = 6 (5 + 1). Uran ist in Form eines Doma-Oktaeders, Niob1 pentagonal-bipyramidal, Niob2 verzerrt oktaedrisch von Sauerstoff umgeben.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/zaac.19946200620
