032ChemInform Abstract The title compounds M(AuF6)2 (M: Mg, Ca, Sr, Ba) are prepared by reacting MF2, Au and KrF2 in anhydrous HF at 0-20 rc C. Their structures are elucidated by Raman spectroscopy and by powder XRD. The compounds Mg(AuF6)2 and Ca(AuF6)2 elong to the space group P4 with Z=1 and the compounds Sr(AuF6)2 and Ba(AuF6)2 crystallize in the space group P43m or P23 (no distinction can be made, so far) with Z=4. The structure of the four compounds consists of AuF6-octahedra and M2+ cations. Further eatures of the structures are discussed.

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Abstract. The anisotropy of the ionic conductivity and permittivity of (1) BaRzF 8 (R = rare earth element) single crystals with monoclinic BaTm2F 8 structure and of (2) (~-YF 3 structured) rare earth trifluorides is studied. Single crystals, eutectic composites and ceramics are investigated in a broad temperature range. In the monoclinic BaR2F 8 crystals, a pronounced anisotropy of the ionic conductivity and a slight anisotropy of the permittivity are found. The fastest ionic transport with the lowest activation energy (0.563 eV) and the highest value of the permittivity are observed along the a axis. The temperature dependencies of the fluoride ion conductivities of various orthorhombic rare earth trifluorides differ only slightly from one another. For the bulky single crystals, the conductivity at 500 ~ and the conduction activation enthalpy are equal to 1.1(4)x10 -5 S/cm and 0.75(3) eV, respectively. The ionic conductivity is almost isotropic, but the anisotropy of the permittivity is significant. For the fluorides of both structural types, plausible conduction mechanisms are proposed, networks of most probable conduction paths are presented and the origin of the observed anisotropy of the ionic conductivity is elucidated.

Synthesis and Properties of Cesium and Sodium Cuprates.-The formation of the cuprates(II) and cuprates(III) specified in the title is reinvestigated for the systems M2O2 (M: Na,Cs)-CuO between 200 and 800 • C under oxygen. At lower temp. (200-600 • C) mixtures of the cuprates(II) and the cuprates(III) are formed which are converted into the single-phase cuprates(II) on heating to 800 . degree.C under air. Both cuprates(II), M2CuO2, crystallize in the tetragonal system with Z = 2. Their structures are composed of planar layers of Cu and O atoms. The O atoms are at the junctions of an endless square lattice and the Cu atoms are in the centers of every second of the square cells. The alkali atoms are located between the layers. -(KOPELEV, N. S.; VAL'KOVSKII, M. D.; POPOV, A. I.; OSKOLOK, K. V.; Zh. Neorg. Khim. 36 (1991) 11, 2745-2752; Inst. obshch. neorg. khim. im. Kurnakova Akad. nauk SSSR, USSR; RU)