title: Ln18Li8Rh5O39 (Ln = La, Pr): a mixed-metal oxide with a charge-ordered arrangement of Rh3+ and Rh4+.
abstract: Polycrystalline samples of Ln18Li8Rh5O39 (Ln = La, Pr) have been synthesized by the ceramic method and characterized by X-ray and neutron diffraction. The compounds crystallize in the cubic space group Pmn, with a0 approximately 12.1 Angstroms. The unit cell contains four intersecting 111 chains, each comprised of an alternating sequence of face-sharing RhO6 octahedra and LiO6 trigonal prisms. The octahedra located at the points of intersection contain Rh4+, whereas the remainder contain Rh3+; the compounds thus contain a charge-ordered arrangement of the two cations. The polyhedral chains are enclosed in tunnels formed by the Ln-O sublattice. The magnetic properties of the two new compounds are discussed briefly: both are paramagnetic over the temperature range 5 < TK < 300.
authors.affiliation: Inorganic Chemistry Laboratory, Oxford University, UK.
authors.forename: Philip P C
authors.initials: PP
authors.lastname: Frampton
authors.forename: Peter D
authors.initials: PD
authors.lastname: Battle
authors.forename: Clemens
authors.initials: C
authors.lastname: Ritter