β-Cu3Fe4(VO4)6: Structural Study and Relationships; Physical Properties

✍ Scribed by M.A. Lafontaine; J.M. Grenéche; Y. Laligant; G. Férey

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 400 KB
• Volume: 108
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1994.1001

✦ Synopsis

A new form of (\mathrm{Cu}{3} \mathrm{Fe}{4}\left(\mathrm{VO}{4}\right){6}), different from the mineral lyonsite, has been isolated. It is triclinic (S.G. (\overline{P 1} ; a=6.600(3) \AA), (b=8.048(4) \AA, c=9.759(5) \AA, \alpha=106.08(3)^{\circ}, \beta=103.72(3)^{\circ}), (\left.\gamma=102.28(2)^{\circ}, V=461.8 \AA^{3}, Z=1\right)). This three dimensional compound is characterized by the existence of edge sharing octahedral dimers of iron, connected by (\mathrm{VO}{4}) tetrahedra and two sorts of copper polyhedra: square planes and trigonal bipyramids. Some cationic disorder between octahedral iron and fivefold coordinated copper sites is, however, detected by Mössbauer spectroscopy. This structure is closely related to howardevansite (\mathrm{NaCuFe}{2}\left(\mathrm{VO}{4}\right){3}) and to other phosphates, vanadates, and molybdates of various compositions which can however, be described in a common cell in order to explain the relationships among all these compounds. Finally, physical properties of this copper iron vanadate are given. (\mathrm{Cu}{3}) (\mathrm{Fe}{4}\left(\mathrm{VO}{4}\right){6}) is a semiconductor ( (E_{\mathrm{a}} \sim 0.20 \mathrm{eV}) ). Below (15 \mathrm{~K}), it becomes antiferromagnetic. O 1994 Academic Press, Inc.