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Crystal structures of spinel-type Na2MoO4 and Na2WO4 revisited using neutron powder diffraction

Fortes, AD; (2015) Crystal structures of spinel-type Na2MoO4 and Na2WO4 revisited using neutron powder diffraction. Acta Crystallographica Section E , 71 (Pt 6) pp. 592-596. 10.1107/S2056989015008774. Green open access

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Abstract

Time-of-flight neutron powder diffraction data have been collected from Na2MoO4 and Na2WO4 to a resolution of sin (θ)/λ = 1.25 Å(-1), which is substanti-ally better than the previous analyses using Mo Kα X-rays, providing roughly triple the number of measured reflections with respect to the previous studies [Okada et al. (1974 ▶). Acta Cryst. B30, 1872-1873; Bramnik & Ehrenberg (2004 ▶). Z. Anorg. Allg. Chem. 630, 1336-1341]. The unit-cell parameters are in excellent agreement with literature data [Swanson et al. (1962 ▶). NBS Monograph No. 25, sect. 1, pp. 46-47] and the structural parameters for the molybdate agree very well with those of Bramnik & Ehrenberg (2004 ▶). However, the tungstate structure refinement of Okada et al. (1974 ▶) stands apart as being conspicuously inaccurate, giving significantly longer W-O distances, 1.819 (8) Å, and shorter Na-O distances, 2.378 (8) Å, than are reported here or in other simple tungstates. As such, this work represents an order-of-magnitude improvement in precision for sodium molybdate and an equally substantial improvement in both accuracy and precision for sodium tungstate. Both compounds adopt the spinel structure type. The Na(+) ions have site symmetry .-3m and are in octa-hedral coordination while the transition metal atoms have site symmetry -43m and are in tetra-hedral coordination.

Type: Article
Title: Crystal structures of spinel-type Na2MoO4 and Na2WO4 revisited using neutron powder diffraction
Location: England
Open access status: An open access version is available from UCL Discovery
DOI: 10.1107/S2056989015008774
Publisher version: http://dx.doi.org/10.1107/S2056989015008774
Language: English
Additional information: This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
Keywords: neutron powder diffraction, sodium molybdate, sodium tungstate
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/1468469
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