Synthesis and structure of some MII/MIII mixed fluorides with pyrochlore and weberite related structures

Abstract

New NH4MIIMIIIF6 and M IIMIIIF5 · 2H2O compounds with the pyrochlore and weberite structures, respectively, are reported. Structures of NH4CoCrF6, AlZnF5 · 2H2O, and GaMnF5 · 2H2O were refined using X-ray diffraction data from single crystals. The structures of Mg IIAlIIIF5 · H2O and NH 4MgIIAlIIIF6 were refined from powder X-ray diffraction data. Magnetic susceptibility data indicates antiferromagnetic ordering in NH4CoIIVIIIF 6 at 7 K but no ordering in NH4CoIICr IIIF6 down to 4.2 K. Electrical conductivity presumably due to protons was observed in MgAlF5 · (H2O) 2. © 2006 Verlag der Zeitschrift für Naturforschung.