Synthesis and Structure of Some MII/MIII Mixed Fluorides with Pyrochlore and Weberite Related Structures

Abstract

New NH4MIIMIIIF6 and MIIMIIIF5 ・ 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 MgIIAlIIIF5 ・H2O and NH4MgIIAlIIIF6 were refined from powder X-ray diffraction data. Magnetic susceptibility data indicates antiferromagnetic ordering in NH4CoIIVIIIF6 at 7 K but no ordering in NH4CoIICrIIIF6 down to 4.2 K. Electrical conductivity presumably due to protons was observed in MgAlF5 ・ (H2O)2.