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Synthesis and Structural, Magnetic and Electrical Characterization of the Reduced Oxoniobates BaNb8O14, EuNb8O14, Eu2Nb5O9 and EuxNbO3 (x = 0.7, 1.0).
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1995 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, Vol. 226, 24-30 p.Article in journal (Refereed) Published
Abstract [en]

Powder samples of the reduced oxoniobates Eu0.7NbO3, EuNbO3, Eu2Nb5O9, EuNb8O14 and BaNb8O14 have been synthesised. EuNbO3 and Eu0.7NbO3 adopt the perovskite type structure (space group Pm3m) with unit cell parameters a = 4.021 (1) and 3.981 (3) Angstrom, respectively. Eu,Nb,Og exhibits an intergrowth structure which can be described as alternating slabs of NbO and EuNbO3. It crystallises in P4/mmm with a = 4.131(1) and c = 12.043(5) Angstrom. EuNb8O14 and the here synthesised modification of BaNb8O14 is isostructural with SrNb8O14. The structures of EuNb8O14 and BaNb8O14 have been refined from X-ray powder diffraction data with the Rietveld technique, They have the unit cell parameters a = 9.2272(1), b = 10.2647(2), c = 5.9381(1) and a = 9.3451(1), b = 10.2689(2), c = 5.9470(4) Angstrom, (space group Pbam), respectively. In all the studied compounds AO(12) cuboctahedra (A = Eu, Ba) form either chains (in ANb(8)O(14)), double layers (in Eu2Nb5O9) or three-dimensional nets (in EuNbO3 and Eu0.7NbO3). Magnetic susceptibility measurements show temperature independent paramagnetism for BaNb8O14, while the susceptibilities of the Eu niobates follow Curie-Weiss laws with effective magnetic moments in good agreement with the expected mu(eff)=7.9 mu(B) for EU(2+). Eu0.7NbO3 and Eu1.0NbO3 exhibit ferromagnetic ordering below 4 K. BaNb8O14 and EuNb8O14 are semiconductors, while Eu2Nb5O9, EuNbO3 and Eu0.7NbO3 are metallic.

Place, publisher, year, edition, pages
1995. Vol. 226, 24-30 p.
Keyword [en]
MAGNETIC CHARACTERIZATION, ELECTRICAL CHARACTERISTICS, REDUCED OXONIOBATES, niobium, Nb;europium, Eu;barium, Ba;structure (solids and liquids);electric properties, superconductors, semiconductors
National Category
Materials Chemistry
Research subject
Materials Chemistry
URN: urn:nbn:se:su:diva-43898OAI: diva2:371118
Available from: 2010-11-18 Created: 2010-10-29 Last updated: 2011-11-16Bibliographically approved

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Svensson, Gunnar
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Department of Materials and Environmental Chemistry (MMK)
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