title: Nonstoichiometry in Strontium Uranium Oxide: Understanding the Rhombohedral-Orthorhombic Transition in SrUO4.
abstract: In situ neutron and synchrotron X-ray diffraction studies demonstrate that SrUO4 acts as an oxygen transfer agent, forming oxygen vacancies under both oxidizing and reducing conditions. Two polymorphs of SrUO4 are stable at room temperature, and the transformation between these is observed to be associated with thermally regulated diffusion of oxygen ions, with partial reduction of the U(6+) playing a role in both the formation of oxygen deficient α-SrUO4-δ and its subsequent transformation to stoichiometric β-SrUO4. This is supported by ab initio calculations using density functional theory calculations. The oxygen vacancies play a critical role in the first order transition that SrUO4 undergoes near 830 °C. The changes in the oxidation states and U geometry associated with the structural phase transition have been characterized using X-ray absorption spectroscopy, synchrotron X-ray diffraction, and neutron diffraction.
authors: School of Chemistry, The University of Sydney , Sydney, New South Wales 2006, Australia.
authors: Gabriel L
authors: GL
authors: Murphy
authors: School of Chemistry, The University of Sydney , Sydney, New South Wales 2006, Australia.
authors: Brendan J
authors: BJ
authors: Kennedy
authors: Australian Synchrotron , 800 Blackburn Road, Clayton, Victoria 3168, Australia.
authors: Justin A
authors: JA
authors: Kimpton
authors: Australian Synchrotron , 800 Blackburn Road, Clayton, Victoria 3168, Australia.
authors: Qinfen
authors: Q
authors: Gu
authors: Australian Synchrotron , 800 Blackburn Road, Clayton, Victoria 3168, Australia.
authors: Bernt
authors: B
authors: Johannessen
authors: Institute of Energy and Climate Research, IEK-6 Nuclear Waste Management and Reactor Safety, Forschungszentrum Jülich GmbH , Wilhelm-Johnen-Strasse, 52428 Jülich, Germany.|JARA High-Performance Computing , Schinkelstrasse 2, 52062 Aachen, Germany.
authors: George
authors: G
authors: Beridze
authors: Institute of Energy and Climate Research, IEK-6 Nuclear Waste Management and Reactor Safety, Forschungszentrum Jülich GmbH , Wilhelm-Johnen-Strasse, 52428 Jülich, Germany.|JARA High-Performance Computing , Schinkelstrasse 2, 52062 Aachen, Germany.
authors: Piotr M
authors: PM
authors: Kowalski
authors: Institute of Energy and Climate Research, IEK-6 Nuclear Waste Management and Reactor Safety, Forschungszentrum Jülich GmbH , Wilhelm-Johnen-Strasse, 52428 Jülich, Germany.|JARA High-Performance Computing , Schinkelstrasse 2, 52062 Aachen, Germany.
authors: Dirk
authors: D
authors: Bosbach
authors: Australian Nuclear Science and Technology Organisation , Lucas Heights, New South Wales 2234, Australia.
authors: Maxim
authors: M
authors: Avdeev
authors: Australian Nuclear Science and Technology Organisation , Lucas Heights, New South Wales 2234, Australia.
authors: Zhaoming
authors: Z
authors: Zhang