Investigation of the ternary systems containing A F-BaF2-MF2 (A = Li, Na; M = Mn, Fe, Co) shows the existence of a new series of perovskite-type structures Na4BaxM4-xF12 (M = Mn, Fe, Co) and Na4-xLixBaxCo4-xF12, isostructural to Na4BaxFe4-xF12 (x = 0.84), the structure of which has been determined from X-ray single-crystal data. In each system, the homogeneity range of the phases has been determined. The space group is Im3 with a unit-cell constant which is twice that of the parent ABX3 perovskite. The cationic distribution in the different sites can be expressed by the detailed formula [BaxNaI-x]Na3(Fe4-xNax)F12 (x = 0.84). A Rietveld profile analysis from X-ray spectra for the cobalt phases and from neutron diffraction spectra for the manganese and iron phases confirmed the same cationic distribution. The magnetic properties of these fluorides, at low temperature, are characteristic of a 3D antiferromagnetic order. The magnetic structures of Na4BaxMn4-xF12 (x = 0.75) and Na4BaxFe4-xF12 (x = 0.87) have been determined.

The new Ba6Mn2ZnF12Cl6 phase has an hexagonal symmetry (space group P6(3)/m) with a=10.081(1)angstrom c=5.8476(1)angstrom and Z=1. The structure has been refined from 1046 reflections down to R=0.0221, wR=0.0227. It can be described as built up from isolated [ZnCl6]n and [MnF6]n chains parallel to c-axis which are separated from each other by the barium cations in ten-fold coordination. The [ZnCl6]n chains are formed by face sharing octahedra similar to those of the 2H hexagonal perovskite but zinc occupies in a disordered way only one half of the sites. Manganese is located in a fluorine triangular prism (D3h symmetry) which is an unusual environment for this cation. The prisms are associated by face sharing along the c-axis with an 1-1 ordering between occupied and vacant sites. As a consequence manganese atoms are isolated in the chains. This result has been confirmed by magnetic susceptibility measurements, Ba6Mn2ZnF12Cl6 following a Curie law down to 4.2K.

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A new NaBa2Mn3F11 fluoride has been prepared by solid-state reaction. The crystal structure has been determined from X-ray diffraction measurements on a single crystal (R=0.0317, wR=0.0295). The crystal symmetry is rhombohedral, space group R3¯c with the unit cell constants of a=7.003 Å and c=35.466 Å. The most important feature of the structure is the unusual environment of Mn2+, which is located in a pentagonal bipyramid (CN=7). To our knowledge this is the second example of such a surrounding for Mn2+ in fluoride compounds. These bipyramids are linked by edge sharing and constitute [Mn3F11] layers which are perpendicular to the c-axis and separated by the Na+ and Ba2+ cations. The surrounding of the Ba2+ ions is a tricapped trigonal prism. Along the c-axis these prisms form [Ba2F15] pairs by edge sharing. The Na atoms exhibit a distorted cubic environment. Above 40 K the magnetic susceptibility follows a Curie-Weiss law with Θp = − 31.5 K and C=4.1. The broad maximum observed around T=15 K can result from the low dimensionality of the magnetic arrangement (2D).

The crystal structure of NaBaLiNiF6 has been determined from X-ray single crystal data The crystal symmetry is cubic, space group Fm3m, with an unit-cell constant of a = 7.992(1)angstrom. Barium and sodium atoms occupy the A-sites (CN=12) with a small disordering of 10% between the two independent positions. The Li and Ni atoms are statistically disordered in the B-sites. These crystallographic results have been confirmed by magnetic susceptibility measurements and by NMR experiments on F-19, Na-23 and Li-9 nuclei.

The crystal data of Na2BaMn4F12 and Na2BaFe4F12 have been determined by X-ray and neutron diffractions respectively. The crystal symmetry of Na2BaFe4F12 is cubic, space group Im3, with an unit cell constant of a = 8.075Å, which is twice that of a simple ABX3 perovskite. Barium and sodium atoms occupy the A sites (CN  12) of the ideal perovskite structure, while iron atoms are located in the octahedral B sites. In the Im3 space group, the A sites have different point symmetry and therefore the (AF12) polyhedra exhibit different types of distortions. In our case a cationic ordering occurs in those CN=12 sites and the site corresponding to the sodium atoms is not fully occupied. This ordering can be compared with that found in Na4BaCu3F12 (1) . This new perovskite-type structure is closely related to the [AC3](B4)O12 ordered perovskite-like series whose prototype is [NaMn3](Mn4)O12. These results have been confirmed in the case of the Mn compound by powder neutron diffraction studies.

The compound Bi2Sr2CuO6 has been prepared by solid state reaction under inert gas flow (Ar) at 800-degrees-C. It has been observed that the control of the gas flow is a prime necessity to prepare it as single phase. The same results have been obtained when the solid state reaction are made under vacuum. Using electron diffraction and high resolution electron microscopy, it has been possible to deduce the cell-parameters and to index the x-ray pattern. The symmetry is monoclinic (C-centered) with a = 24.451(5)angstrom, b = 5.425(2)angstrom, c = 21.954(5)angstrom and beta = 105.41(1)-degrees. The experimental density confirms the proposed unit-cell parameters and also that the compound does not contain excess of oxygen above the stoichiometric value of six oxygens per formula unit. These results are in good agreement with reference [13]. Bi2Sr2CuO6, which is normally the n = 1 member of the superconducting series A2B2Ca(n-1)Cu(n)O4+2n (A = Sr,Ba;B = Bi,Tl), seems to be a different phase from that expected in this series.