title: The key role of the composition and structural features in fluoride ion conductivity in tysonite Ce1-xSrxF3-xsolid solutions.
abstract: Pure tysonite-type Ce1-xSrxF3-xsolid solutions for 0 ≤ x < 0.15 were prepared by a solid-state route at 900 °C. The cell parameters follow Vegard's laws for 0 ≤ x ≤ 0.10 and the solubility limit is identified (0.10 < xlimit< 0.15). For 0 ≤ x ≤ 0.05, the F2-(Ce,Sr) and F3-(Ce,Sr) bond distances into [Ce1-xSrxF](2-x)+slabs strongly vary with x. This slab buckling is maximum around x = 0.025 and strongly affects the more mobile F1 fluoride ions located between the slabs. The19F MAS NMR spectra show the occurrence of F1-F2,3 exchange at 64 °C. The fraction of mobile F2,3 atoms deduced from the relative intensity of the NMR resonance is maximum for Ce0.99Sr0.01F2.99(22% at 64 °C) while this fraction linearly increases with x for La1-xAExF3-x(AE = Ba, Sr). The highest conductivity found for Ce0.975Sr0.025F2.975(3 × 10-4S cm-1at RT, Ea= 0.31 eV) is correlated to the largest dispersion of F2-(Ce,Sr) and F3-(Ce,Sr) distances which induces the maximum sheet buckling. Such a relationship between composition, structural features and fluoride ion conductivity is extended to other tysonite-type fluorides. The key role of the difference between AE2+and RE3+ionic radii and of the thickness of the slab buckling is established and could allow designing new ionic conductors.
authors.affiliation: CNRS, Univ Bordeaux, ICMCB, UPR 9048, F 33600 Pessac, France. alain.demourgues@icmcb.cnrs.fr.
authors.forename: Belto
authors.initials: B
authors.lastname: Dieudonné
authors.affiliation: CNRS, Univ Bordeaux, ICMCB, UPR 9048, F 33600 Pessac, France. alain.demourgues@icmcb.cnrs.fr and Université du Maine, Institut des Matériaux et des Molécules du Mans (IMMM), UMR CNRS 6283, avenue O. Messiaen, 72085 Le Mans, France.
authors.forename: Johann
authors.initials: J
authors.lastname: Chable
authors.affiliation: Université du Maine, Institut des Matériaux et des Molécules du Mans (IMMM), UMR CNRS 6283, avenue O. Messiaen, 72085 Le Mans, France.
authors.forename: Monique
authors.initials: M
authors.lastname: Body
authors.affiliation: Université du Maine, Institut des Matériaux et des Molécules du Mans (IMMM), UMR CNRS 6283, avenue O. Messiaen, 72085 Le Mans, France.
authors.forename: Christophe
authors.identifier: http://orcid.org/0000-0001-7426-8817
authors.initials: C
authors.lastname: Legein
authors.affiliation: CNRS, Univ Bordeaux, ICMCB, UPR 9048, F 33600 Pessac, France. alain.demourgues@icmcb.cnrs.fr.
authors.forename: Etienne
authors.initials: E
authors.lastname: Durand
authors.affiliation: CNRS, Univ Bordeaux, ICMCB, UPR 9048, F 33600 Pessac, France. alain.demourgues@icmcb.cnrs.fr.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Mauvy
authors.affiliation: CNRS, Univ Bordeaux, ICMCB, UPR 9048, F 33600 Pessac, France. alain.demourgues@icmcb.cnrs.fr.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Fourcade
authors.affiliation: Université du Maine, Institut des Matériaux et des Molécules du Mans (IMMM), UMR CNRS 6283, avenue O. Messiaen, 72085 Le Mans, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Leblanc
authors.affiliation: Université du Maine, Institut des Matériaux et des Molécules du Mans (IMMM), UMR CNRS 6283, avenue O. Messiaen, 72085 Le Mans, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Maisonneuve
authors.affiliation: CNRS, Univ Bordeaux, ICMCB, UPR 9048, F 33600 Pessac, France. alain.demourgues@icmcb.cnrs.fr.
authors.forename: Alain
authors.identifier: http://orcid.org/0000-0002-3828-8498
authors.initials: A
authors.lastname: Demourgues