Hydrothermal synthesis, structure, and characterization of a mixed-valent iron(II/III) phosphate, NaFe{sub 3.67}(PO{sub 4}){sub 3}: A new variation of the alluaudite structure type
- Clemson Univ., SC (United States). Dept. of Chemistry
- Univ. of Missouri, Rolla, MO (United States). Dept. of Chemistry
A mixed-valent Fe(II/III) phosphate, NaFe{sub 3.67}(PO{sub 4}){sub 3}, has been synthesized by high-temperature/high-pressure hydrothermal methods and characterized by single-crystal X-ray diffraction, EDAX, magnetic susceptibility, Moessbauer, infrared, and diffuse reflectance spectroscopies, DTA, and bond valence sum calculations. The compound crystallizes in the monoclinic space group C2/c (No. 15) with a = 11.881(4) {angstrom}, b = 12.564(3) {angstrom}, c = 6.522(2) {angstrom}, {beta} = 115.09(2){degree}, V = 881.7(5) {angstrom}{sup 3}, and Z = 4 with R/R{sub w} = 0.029/0.033. It exhibits a three-dimensional channel-like structure with an open framework that is similar to the naturally occurring iron-containing mineral alluaudite, NaFe{sub 3}(PO{sub 4}){sub 3}. In alluaudite there are two distinct channels, one which contains the sodium cations and the second which remains empty. In the title phase, this second channel is partially occupied by a square-planar iron atom. The Moessbauer spectral parameters are consistent with the structure and indicate that the fully occupied iron sites are octahedral Fe(II) and the square-planar iron is Fe(III). Structural comparisons to a number of phosphates and arsenates that also possess the alluaudite-type structure, including NaCu{sub 4}(AsO{sub 4}){sub 3} and NaMn{sub 4}(AsO{sub 4}){sub 3} are discussed.
- Sponsoring Organization:
- National Science Foundation, Washington, DC (United States)
- OSTI ID:
- 653138
- Journal Information:
- Journal of Solid State Chemistry, Vol. 139, Issue 1; Other Information: PBD: Aug 1998
- Country of Publication:
- United States
- Language:
- English
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