Crystal structure, magnetic susceptibility and Mössbauer spectroscopy of the mixed-valence iron phosphate Na1/2Cu4/3Fe2(PO4)3

Single crystals of a new mixed-valent iron phosphate Na1/2Cu4/3Fe2(PO4)3 have been synthesized by a flux method and structurally characterized from X-ray diffraction data. Crystal data: space group P1¯; a=6.2882(1)Å; b=8.0459(1)Å; c=9.3255(1)Å; α=105.881(1)°α=105.881(1)°; β=107.202(1)°β=107.202(1)°; γ=101.467(1)°γ=101.467(1)°; Z=2Z=2; R1=0.03R1=0.03; wR2=0.093wR2=0.093. The three-dimensional structure was found to be closely related to that of the well known Howardevansite structural type. It results from infinite chains of CuO5 and FeO6 polyhedra, joined together by (Cu,□)O6 octahedra and PO4 tetrahedra by corner-sharing. The large cavities in framework are occupied by Na+ ions. The magnetic susceptibility study revealed an antiferromagnetic behavior with Neel temperature of approximately 40 K. The Mössbauer spectroscopy confirmed the presence of iron in both +2 and +3 oxidation states.

A view of the infinite zigzag chains in the Na1/2Cu4/3Fe2(PO4)3 structure.Figure optionsDownload as PowerPoint slide