Synthesis and Structure of Some M^II/M^III Mixed Fluorides with Pyrochlore and Weberite Related Structures

Abstract

New NH 4 M II M III F 6 and M II M III F 5 ・ 2H 2 O compounds with the pyrochlore and weberite structures, respectively, are reported. Structures of NH 4 CoCrF 6 , AlZnF 5 ・ 2H 2 O, and GaMnF 5 ・ 2H 2 O were refined using X-ray diffraction data from single crystals. The structures of Mg II Al III F 5 ・H 2 O and NH 4 Mg II Al III F 6 were refined from powder X-ray diffraction data. Magnetic susceptibility data indicates antiferromagnetic ordering in NH 4 Co II V III F 6 at 7 K but no ordering in NH 4 Co II Cr III F 6 down to 4.2 K. Electrical conductivity presumably due to protons was observed in MgAlF 5 ・ (H 2 O) 2 .