Structural investigation of Na3NpO4 and Na3PuO4 using X-ray diffraction and 237Np Mössbauer spectroscopy

A. L. Smith; P. E. Raison; A. Hen; D. Bykov; E. Colineau; J.-P. Sanchez; R. J. M. Konings; A. K. Cheetham

doi:10.1039/C5DT02168E

Structural investigation of Na₃NpO₄ and Na₃PuO₄ using X-ray diffraction and ²³⁷Np Mössbauer spectroscopy†

A. L. Smith,*^ab P. E. Raison,*^a A. Hen,^a D. Bykov,^a E. Colineau,^a J.-P. Sanchez,^cd R. J. M. Konings^a and A. K. Cheetham^b

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* Corresponding authors

^a European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, D-76125 Karlsruhe, Germany
E-mail: als77@cantab.net, philippe.raison@ec.europa.eu

^b Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, UK

^c CEA, INAC-SPSMS, Grenoble, France

^d Université de Grenoble Alpes, INAC-SPSMS, Grenoble, France

Abstract

α-Na₃NpO₄ and α-Na₃PuO₄ exhibit an orthorhombic structure (Z = 8), in space group Fmmm, with lattice parameters a = 13.352(2) Å, b = 9.629(2) Å, and c = 6.673(2) Å for the neptunium compound, and a = 13.302(2) Å, b = 9.634(2) Å, and c = 6.651(2) Å for the plutonium analogue. The corresponding structure has been solved ab initio as no structural analogue could be found in the literature. The pentavalent state of neptunium has moreover been confirmed by ²³⁷Np Mössbauer spectroscopy, and the local structural properties inferred from the X-ray Rietveld refinement have been related to the fitted quadrupole coupling constant and asymmetry parameters. The existence of a low temperature metastable m phase of Na₃NpO₄ and Na₃PuO₄, of the NaCl type, has also been suggested.

$Graphical abstract: Structural investigation of Na3NpO4 and Na3PuO4 using X-ray diffraction and 237Np Mössbauer spectroscopy$

This article is part of the themed collection: In celebration of Tony Cheetham’s 70th birthday

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DOI: https://doi.org/10.1039/C5DT02168E
Article type: Paper
Submitted: 08 Jun 2015
Accepted: 23 Aug 2015
First published: 08 Sep 2015
This article is Open Access

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Dalton Trans., 2015,44, 18370-18377

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Structural investigation of Na₃NpO₄ and Na₃PuO₄ using X-ray diffraction and ²³⁷Np Mössbauer spectroscopy

A. L. Smith, P. E. Raison, A. Hen, D. Bykov, E. Colineau, J.-P. Sanchez, R. J. M. Konings and A. K. Cheetham, Dalton Trans., 2015, 44, 18370 DOI: 10.1039/C5DT02168E

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