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Condensed cluster phases in reduced oxoniobates: synthesis and studies of Sr4−xNb17O26 (x=0.0(1), 0.3(1)) and Eu4−xNb17O26 (x=0.3(1)):  
Institute of Solid State Chemistry, Russian Academy of Science, Ekaterinburg, Russia.
Institute of Solid State Chemistry, Russian Academy of Science, Ekaterinburg, Russia.
Max Planck Institute - Solid State Chemistr, Stuttgart, Germany.
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1997 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, Vol. 256, 129-139 p.Article in journal (Refereed) Published
Abstract [en]

Sr4−xNb17O26 (x=0.0, 0.3) and Eu4−xNb17O26 (x = 0.3) were synthesised from SrCO3/Eu2O3 and Nb2O5 in a vacuum furnace at temperatures up to 1600°C (1500°C for Eu) using acetylene soot or Nb as reducing agents. The synthetic studies show that these phases are only formed via an intermediate disordered ‘phase’ (or phasoid). Sr4−xNb17O26 and Eu4−xNb17O26 are isostructural with Ba4Nb17O26 and crystallise in space group P 4/m (83) with the unit cell parameters for   and and , respectively. The crystal structure can be described as an intergrowth between ANbO3 and NbO. Characteristic building blocks are quadruple chains of corner-sharing Nb6-octahedra. ?The structures of Sr4−xNb17O26 and Eu4−xNb17O26 were refined using X-ray powder diffraction and neutron diffraction data (only Sr4−xNb17O26). The Rietveld refiniments and microanalyses showed x in Eu4−xNb17O26 to be 0.3(l) while the Sr analogue both x= 0.0(1) and 0.3(1) were found. High resolution electron microscopy studies showed that the compounds frequently contained structural defects. The magnetic susceptibility of Eu4−xNb17O26 (x=0.3) shows a Curie-Weiss behaviour, with a magnetic moment in good agreement with the expected μeff=7.9 μB for Eu2+/ The Sr analogie is temperature-independent paramagnetic at room temperature, Sr4−xNb17O26 (x=0.3) and Eu4−xNb17O26 (x=0.3) are metallic, with a resistivity increasing with temperature.

Place, publisher, year, edition, pages
1997. Vol. 256, 129-139 p.
Keyword [en]
synthesis, Nb6O12 clusters, condensed cluster phases
National Category
Materials Chemistry
Research subject
Materials Chemistry
URN: urn:nbn:se:su:diva-43892OAI: diva2:371522
Available from: 2010-11-21 Created: 2010-10-29 Last updated: 2011-11-02Bibliographically approved

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Department of Materials and Environmental Chemistry (MMK)
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