A new 3-D incommensurate structure in the Bi-Re-O system

School of Chemistry, University of Sydney
â—‹Neeraj Sharma Chris D Ling

Here we report the discovery and characterisation of a new phase in the Bi-Re-O system that exhibits rare three-dimensionally incommensurate structural and compositional modulations. The phase has the cubic fluorite-type substructure of the high-temperature form of bismuth oxide, d-Bi2O3. Rhenium becomes the latest in a series of transition metal dopants known to give rise to 3-D incommensurate modulations in bismuth oxides, the others being Nb(V), Ta(V), Mo(VI), and Cr(VI)[1],[2],[3]. Electron and X-ray powder diffraction data indicate a modulation vector of ~0.29<111>*F, and energy-dispersive X-ray analysis using scanning electron microscopy indicate a Bi-Re ratio of ~5.9:1. These results suggest that the new phase has more in common with the Mo(VI) and Cr(VI) doped bismuth oxides than with the Nb(V) and Ta(V) cases, suggesting an oxidation state of Re(VI). This is backed up by magnetic susceptibility data that shows a weak antiferromagnetic signal below ~150 K, attributable to interactions among the single unpaired d electrons of Re(VI). Further investigations to confirm the valence state of rhenium are ongoing and will be presented along with further structural data.


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