Crystal chemistry of the divalent cation in alluaudite-type phosphates: A structural and infrared spectral study of the Na{sub 1.5}(Mn{sub 1-x}M{sub x}{sup 2+}){sub 1.5}Fe{sub 1.5}(PO{sub 4}){sub 3} solid solutions (x=0 to 1, M{sup 2+}=Cd{sup 2+}, Zn{sup 2+})

Journal Article · Thu May 15 00:00:00 EDT 2008 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2008.02.035· OSTI ID:21128306

Hatert, Frederic ^[1]

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1. Laboratoire de Mineralogie, Universite de Liege, Batiment B18, B-4000 Liege (Belgium)

Compounds of the Na{sub 1.5}(Mn{sub 1-x}M{sub x}{sup 2+}){sub 1.5}Fe{sub 1.5}(PO{sub 4}){sub 3} (M{sup 2+}=Cd{sup 2+}, Zn{sup 2+}) alluaudite-type solid solutions were synthesized by solid-state reactions in air, between 800 and 900 deg. C, and were investigated by X-ray powder diffraction and infrared spectroscopy. The site occupancy factors of the Na{sub 1.5}(Mn{sub 1-x}Cd{sub x}{sup 2+}){sub 1.5}Fe{sub 1.5}(PO{sub 4}){sub 3} compounds, obtained from the Rietveld refinements of the X-ray powder patterns, indicate that the replacement of Mn{sup 2+} by Cd{sup 2+} takes place on the M(1) site for x=0.25 and 0.50, and then on the M(1) and M(2) sites for x=0.75 and 1.00. Small amounts of Cd{sup 2+} were also detected on the A(1) site, compensated by small amounts of Na{sup +} occurring on M(1). This partially disordered distribution is probably due to the similar effective ionic radii of Cd{sup 2+} and Na{sup +}. The cationic distributions in the Na{sub 1.5}(Mn{sub 1-x}Zn{sub x}{sup 2+}){sub 1.5}Fe{sub 1.5}(PO{sub 4}){sub 3} solid solution indicate that Zn{sup 2+} was first introduced in the M(2) site, before to replace Mn{sup 2+} in the M(1) site. The unit-cell parameters show a significant increase when Mn{sup 2+} is replaced by Cd{sup 2+}, and a significant decrease when it is replaced by Zn{sup 2+}. The variations of the {beta} angle were also correlated with the M(1)-M(2) distances. The infrared spectra show the displacement of an absorption band at ca. 400-425 cm{sup -1}, which is assigned to the vibrations of the M{sup 2+} cations localized on the M(1) site. This assignment is confirmed by the excellent correlations between the M(1)-O bond distances and the energy of the absorption band. - Graphical abstract: The crystal structure of Na{sub 1.5}Zn{sub 1.5}Fe{sup 3+}{sub 1.5}(PO{sub 4}){sub 3}.

• OSTI ID: 21128306
• Journal Information: Journal of Solid State Chemistry, Vol. 181, Issue 5; Other Information: DOI: 10.1016/j.jssc.2008.02.035; PII: S0022-4596(08)00118-7; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION
ABSORPTION SPECTROSCOPY
BOND LENGTHS
CADMIUM COMPOUNDS
CADMIUM IONS
CRYSTAL STRUCTURE
CRYSTALS
INFRARED SPECTRA
IRON COMPOUNDS
MANGANESE COMPOUNDS
MANGANESE IONS
PHOSPHATES
SODIUM COMPOUNDS
SODIUM IONS
SOLID SOLUTIONS
X-RAY DIFFRACTION
ZINC COMPOUNDS
ZINC IONS