PHASE RELATIONS IN THE SYSTEM UO$sub 2$-UO$sub 3$-Y$sub 2$$O$$sub 3$

Journal Article · Tue Apr 21 04:00:00 EST 1964 · Journal of the American Ceramic Society (U.S.)

DOI:https://doi.org/10.1111/j.1151-2916.1964.tb14386.x· OSTI ID:4052470

Bartram, S F; Juenke, E F; Aitken, E A

Phase relations in the system UO/sub 2/--UO/sub 3/--Y/sub 2/O/sub 3/, particu larly in the Y/sub 2/O/sub 3/-rich region, were examined by x-ray and chemical analyses of reacted powders heated at temperatures up to 1700 deg C in H/ sub 2/, CO/sub 2/--CO, and air. Four phases were identified in the system at temperntures between 1000 deg and 1700 deg C: U/sub 3/O/sub 8/, face-centered cubic solid solution. body-centered cubic solid solution, and a rhombohedral phase of composition (U,Y)/sub 7/O/sub 12/ ranging from 52.5 to 75 mole % Y/sub 2/ O/sub 3/. The rhombohedral phase oxidized to a second rhombohedral phase with a nominal composition (U,Y)/sub 8/O/sub 15/ at temperatures below 1000 deg C. This phase transformed to a face-centered cubic phase after heating in air above 1000 deg C. The solubility of UO/sub 2/ in the body-centered cubic phase is about 14 mole% between 1000 and 1700 deg C but decreases to zero as the uranium approaches the hexavalent oxidation state. The solubility of Y/sub 2/O/sub 3/ in the facecertered cubic solid solution ranges from 0 to 50 mole % Y/sub 2/O/sub 3/ under reducing conditions and from 33 to 60 mole % Y/sub 2/O/sub 3/ under oxidizing conditions at 1000 deg C. At temperatures above 1000 deg C, the face- certered cubic solid solution is limited by a filled fluorite lattice of composition (U,Y)O/sub 2/. For low-yttria content, oxidation at low temperatures (<300 deg C) permits additional oxygen to be retained in the structure to a composition approaching (U,Y)O/sub 2.2.5/. A tentative ternary phase diagram for the system UO/sub 2/-UO/sub 3/Y/sub 2/O/sub 3/ is presented and the change in lattice parameter and in cell volume for the solid-solution phases is correlated with the composition. (auth)

• Research Organization: General Electric Co., Cincinnati
• Sponsoring Organization: USDOE
• NSA Number: NSA-18-018370
• OSTI ID: 4052470
• Journal Information: Journal of the American Ceramic Society (U.S.), Journal Name: Journal of the American Ceramic Society (U.S.) Vol. Vol: 47; ISSN JACTA
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

AIR
CALCIUM FLUORIDES
CARBON DIOXIDE
CARBON MONOXIDE
CONFIGURATION
FLUORITE
HEATING
HIGH TEMPERATURE
HYDROGEN
LATTICES
METALS, CERAMICS, AND OTHER MATERIALS
MINERALS
OXIDATION
PHASE DIAGRAMS
POWDERS
QUALITATIVE ANALYSIS
SOLID SOLUTIONS
SOLUBILITY
TEMPERATURE
URANIUM DIOXIDE
URANIUM TRIOXIDE
VOLUME
X RADIATION
YTTRIUM OXIDES