title: Analysis of the local structure of phosphorus-substituted LAMOX oxide ion conductors.
abstract: The effect of partial substitution of molybdenum by phosphorus on the global and local structural arrangement of the fast oxide-ion conductor La(2)Mo(2)O(9) (LAMOX) has been studied by X-ray powder diffraction as well as (139)La and (31)P solid state NMR. The diffraction patterns show that La(2)Mo(2-y)P(y)O(9-y/2) forms a solid solution at low phosphorus concentrations, and that there is a structural phase transition upon increasing phosphorus concentration. This phase transition is also reflected in (139)La and (31)P NMR spectra. The possibility to excite (31)P multiple-quantum coherences of one of the (31)P NMR signals gives evidence of an accumulation of phosphorus atoms on neighbouring Mo-type sites already before formation of three-dimensional precipitates. On the basis of our X-ray and NMR results we propose a possible structural arrangement of the compound La(2)Mo(2-y)P(y)O(9-y/2) that explains the experimental observations by crystal twinning.
authors.affiliation: LUNAM Université, Université du Maine, UMR CNRS 6283, Institut des Molécules et Matériaux du Mans (IMMM), Olivier Messiaen, F-72085 Le Mans Cedex, France.
authors.forename: Bholanath
authors.initials: B
authors.lastname: Pahari
authors.forename: Noureddine
authors.initials: N
authors.lastname: Mhadhbi
authors.forename: Gwenaël
authors.initials: G
authors.lastname: Corbel
authors.forename: Philippe
authors.initials: P
authors.lastname: Lacorre
authors.forename: Jens
authors.initials: J
authors.lastname: Dittmer