Title: Triclinic-Cubic Phase Transition and Negative Expansion in the Actinide IV (Th, U, Np, Pu) Diphosphates
Authors: WALLEZ GRAISON PhilippeDACHEUX NicolasCLAVIER NicolasBYKOV DENISDELEVOYE LaurentPOPA KarinBREGIROUX D.FITCH AndrewKONINGS Rudy
Citation: INORGANIC CHEMISTRY vol. 51 no. 7 p. 4314-4322
Publisher: AMER CHEMICAL SOC
Publication Year: 2012
JRC N°: JRC67988
ISSN: 0020-1669
URI: http://pubs.acs.org/doi/abs/10.1021/ic300036y
http://publications.jrc.ec.europa.eu/repository/handle/JRC67988
DOI: 10.1021/ic300036y
Type: Articles in periodicals and books
Abstract: The AnP2O7 diphosphates (An = Th, U, Np, Pu) have been synthesized by various routes depending on the stability of the AnIV cation and its suitability for the unusual octahedral environment. Synchrotron and X-ray diffraction, thermal analysis, Raman spectroscopy and 31P nuclear magnetic resonance reveal them as a new family of diphosphates which probably includes the recently studied CeP2O7. Although they adopt at high temperature the same cubic archetypal cell as the other known MP2O7 diphosphates, they differ by a very faint triclinic distortion at room temperature that results from an ordering of the P2O7 units, as shown using highresolution synchrotron diffraction for UP2O7. The uncommon triclinic-cubic phase transition is first-order, and its temperature is very sensitive to the ionic radius of AnIV. The conflicting effects which control the thermal variations of the P-O-P angle are responsible for a strong expansion of the cell followed by a contraction at higher temperature. This inversion of expansion occurs at a temperature significantly higher than the phase transition, at variance with the parent compounds with smaller MIV cations in which the two phenomena coincide. As shown by various approaches, the P-Ob-P linkage remains bent in the cubic form.
JRC Directorate:Nuclear Safety and Security

Files in This Item:
There are no files associated with this item.


Items in repository are protected by copyright, with all rights reserved, unless otherwise indicated.