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)) / Zubkov VG,Pereliaev VA,Tyutyunnik AP,Kohler J,Simon A,Svensson G // JOURNAL OF ALLOYS AND COMPOUNDS. - 1997. - V. 256, l. 1-2. - P. 129-139.

ISSN/EISSN:

0925-8388 / 1873-4669

Type:

Article

Abstract:

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 degrees C (1500 degrees C for Eu) using acetylene soot or Nh 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 x = 0.3: a = 12.023(1) Angstrom, c = 4.1411(4) Angstrom and a = 12.015(2) Angstrom, c = 4.135(1) Angstrom, Z = 1, respectively. The crystal structure can be described as an intergrowth between ANbO(3) and NbO. Characteristic building blocks are quadruple chains of corner-sharing Nb-6-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 refinements and microanalyses showed x in Eu4-xNb17O26 to be 0.3(1) while in 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 mu(eff) = 7.9 mu(B) for Eu2+. The Sr analogue 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. (C) 1997 Elsevier Science S.A.

Author keywords:

synthesis; Nb6O12 clusters; condensed cluster phases CRYSTAL-STRUCTURE; POWDER

DOI:

10.1016/S0925-8388(96)03024-1

Web of Science ID:

ISI:A1997XJ45000028

Соавторы в МНС:

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Другие поля

Поле	Значение
Month	JUL 5
Publisher	ELSEVIER SCIENCE SA
Address	PO BOX 564, 1001 LAUSANNE, SWITZERLAND
Language	English
EISSN	1873-4669
Keywords-Plus	CRYSTAL-STRUCTURE; POWDER
Research-Areas	Chemistry; Materials Science; Metallurgy \& Metallurgical Engineering
Web-of-Science-Categories	Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy \& Metallurgical Engineering
ResearcherID-Numbers	Tyutyunnik, Alexander/P-2230-2015
Number-of-Cited-References	21
Usage-Count-Since-2013	5
Journal-ISO	J. Alloy. Compd.
Doc-Delivery-Number	XJ450