Oxidation/reduction studies on Zr{sub y}U{sub 1-y}O{sub 2+x} and delineation of a new orthorhombic phase in U-Zr-O system

Journal Article · Fri Aug 15 04:00:00 EDT 2008 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2008.03.039· OSTI ID:21128385

Kulkarni, N K; Krishnan, K ^[1]; Achary, S N; Tyagi, A K ^[2]

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1. Fuel Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)
2. Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

In this communication, we report the oxidation and reduction behavior of fluorite type solid solutions in U-Zr-O. The maximum solubility of ZrO{sub 2} in UO{sub 2} lattice could be achieved with a mild oxidizing followed by reducing conditions. The role of valency state of U is more dominating in controlling the unit cell parameters than the incorporated interstitial oxygen in the fluorite lattice. The controlled oxidation studies on U-Zr-O solid solutions led to the delineation of a new distorted fluorite lattice at the U:Zr=2:1 composition. The detailed crystal structure analysis of this ordered composition Zr{sub 0.33}U{sub 0.67}O{sub 2.33} (ZrU{sub 2}O{sub 7}) has been carried from the powder XRD data. This phase crystallizes in an orthorhombically distorted fluorite type lattice with unit cell parameters: a=5.1678(2), b=5.4848(2), c=5.5557(2) A and V=157.47(1) A{sup 3} (Space group: Cmcm, No. 63). The metal ions have distorted cubical polyhedra with anion similar to the fluorite structure. The excess anions are occupied in the interstitial (empty cubes) of the fluorite unit cell. The crystal structure and chemical analyses suggest approximately equal fractions of U{sup 4+} and U{sup 6+} in this compound. The details of the thermal stability as well as kinetics of formation and oxidation of ZrU{sub 2}O{sub 7} are also studied using thermogravimetry. - Graphical abstract: Local surrounding of M ions in Zr{sub 0.33}U{sub 0.67}O{sub 2.33}.

• OSTI ID: 21128385
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 8 Vol. 181; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ANIONS
FLUORITE
INTERSTITIALS
KINETICS
ORTHORHOMBIC LATTICES
OXIDATION
REDUCTION
SOLID SOLUTIONS
SOLUBILITY
SPACE GROUPS
THERMAL GRAVIMETRIC ANALYSIS
URANATES
URANIUM DIOXIDE
URANIUM IONS
X-RAY DIFFRACTION
ZIRCONIUM OXIDES