title: Structure determination of La18W10O57.
abstract: We report the synthesis, structure determination, and structure analysis of La(18)W(10)O(57), which presents 52.65 WO(3) mol % in the binary system La(2)O(3)-WO(3) in place of the previous reported compound: La(14)W(8)O(45), 53.3 WO(3) mol %. The structure has been determined from synchrotron and laboratory X-ray, neutron, and electron diffraction data. This tungstate crystallizes in the non-centrosymmetric hexagonal space group (no. 190) P62c, with Z = 2, a = 9.0448(1) A, c = 32.6846(3) A, and a measured density of 7.28(3) g x cm(-3). The structure consists of [WO(6)] octahedra, isolated or sometimes sharing a face, and unusual tungsten [WO(6)] trigonal prisms. This compound presents a subcell c' = c/6 = 5.45 A. Polytypism has been observed concerning this compound. Transmission electronic microscopy, ionic conductivity, and thermal expansion have been explored.
authors: Laboratoire des Oxydes et Fluorures, UMR-CNRS 6010, Université du Maine, 72085 Le Mans Cedex 9, France. marie-helene.chambrier.etu@univ-lemans.fr
authors: Marie-Hélène
authors: MH
authors: Chambrier
authors: Armel
authors: A
authors: Le Bail
authors: Stéphanie
authors: S
authors: Kodjikian
authors: Emmanuelle
authors: E
authors: Suard
authors: François
authors: F
authors: Goutenoire