Synthesis and Structural, Magnetic and Electrical Characterization of the Reduced Oxoniobates BaNb8O14, EuNb8O14, Eu2Nb5O9 and EuxNbO3 (x = 0.7, 1.0).
1995 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, Vol. 226, 24-30 p.Article in journal (Refereed) Published
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.
MAGNETIC CHARACTERIZATION, ELECTRICAL CHARACTERISTICS, REDUCED OXONIOBATES, niobium, Nb;europium, Eu;barium, Ba;structure (solids and liquids);electric properties, superconductors, semiconductors
Research subject Materials Chemistry
IdentifiersURN: urn:nbn:se:su:diva-43898OAI: oai:DiVA.org:su-43898DiVA: diva2:371118