Structural, thermal, magnetic and electrical studies of the iron oxophosphate Rb{sub 7}Fe{sub 7}(PO{sub 4}){sub 8}O{sub 2}.2H{sub 2}O

Journal Article · Wed Sep 15 00:00:00 EDT 2010 · Materials Research Bulletin

DOI:https://doi.org/10.1016/J.MATERRESBULL.2010.05.008· OSTI ID:22207384

Hidouri, Mourad ^[1]; Lajmi, Besma; Gmati, Nadia ^[1]; Wattiaux, Alain ^[2]; Nenert, Gwilherm; Ritter, Clemens ^[3]; Fournes, Leopold; Darriet, Jacques ^[2]; Lopez, Maria Luisa; Pico, Carlos ^[4]; Amara, Mongi B. ^[1]

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1. UR Materiaux Inorganiques, Faculte des Sciences, 5019, rue de l'environnement, Monastir (Tunisia)
2. CNRS, Universite de Bordeaux, ICMCB, 87 avenue du Dr. A. Schweitzer, Pessac, F-33608 (France)
3. ILL, Diffraction Group, BP 156, 6 rue Jules Horowitz, 38042, Grenoble Cedex 9 (France)
4. Departamento de Quimica Inorganica I, Facultad de Ciencias Quimicas, Universidad Complutense, 28040 Madrid (Spain)

A new iron oxophosphate of composition Rb{sub 7}Fe{sub 7}(PO{sub 4}){sub 8}O{sub 2}.2H{sub 2}O has been synthesized and studied by X-ray diffraction, TG and DTA analysis, magnetic susceptibility, neutron diffraction, Moessbauer spectroscopy and ionic conductivity. This compound crystallizes in the monoclinic system with the P2{sub 1}/c space group and the unit cell parameters a = 8.224(8) A, b = 22.162(6) A, c = 9.962(6) A and {beta} = 109.41(8){sup o}. Its structure is built up from Fe{sub 7}O{sub 32} clusters of edge- and corner-sharing FeO{sub 5} and FeO{sub 6} polyhedra. Neighboring clusters are connected by the phosphate tetrahedra to form a three-dimensional framework. The Rb{sup +} cations and the water molecules are occupying intersecting tunnels parallel to a and c. The presence of water molecules was confirmed by TG and DTA analysis. The magnetic susceptibility measurements have shown the existence of antiferromagnetic ordering below 22 K with a weak ferromagnetic component. Additionally, these measurements show evidence for a strong magnetic frustration characterized by |{theta}/T{sub N}| {approx} 12. Powder neutron diffraction study confirms the presence of a long range antiferromagnetic order coupled to a weak ferromagnetic component along the b-axis. The strongly reduced magnetic moments extracted from the refinement support the existence of a magnetically frustrated ground state. The Moessbauer spectroscopy results confirmed the presence of only Fe{sup 3+} ions in both five and six coordination. The ionic conductivity measurements led to activation energy of 0.81 eV, a value that agrees with the obtained for other rubidium phosphates.

• OSTI ID: 22207384
• Journal Information: Materials Research Bulletin, Vol. 45, Issue 9; Other Information: Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ACTIVATION ENERGY
ANTIFERROMAGNETISM
CATIONS
DIFFERENTIAL THERMAL ANALYSIS
IRON IONS
IRON OXIDES
MAGNETIC MOMENTS
MAGNETIC SUSCEPTIBILITY
MOESSBAUER EFFECT
MONOCLINIC LATTICES
NEUTRON DIFFRACTION
POWDERS
RUBIDIUM IONS
RUBIDIUM PHOSPHATES
SPACE GROUPS
SPECTROSCOPY
X-RAY DIFFRACTION