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Crystal chemistry of some monazite-structured phosphates and silicates

Technical Report ·
OSTI ID:6323579
; ; ;
Ca/sub 0/ /sub 5/U/sub 0/ /sub 5/PO/sub 4/ can be synthesized phase-pure in a neutral atmosphere or a closed system at about 1200/sup 0/C by ceramic techniques, and it forms complete solid solutions with Ca/sub 0/ /sub 5/Th/sub 0/ /sub 5/PO/sub 4/ and NdPO/sub 4/. Uranium appears to occur in monazite essentially in only the tetravalent state. The possible role of some other ions in monazite was also studied. Monazite prepared at 1200/sup 0/C in air was observed to incorporate cerium as 3+ and not 4+ even when charge compensation mechanisms for Ce/sup 4 +/ inclusion were present. The consequences of this phenomenon for the use of monazite structure-type solid solutions for transuranic nuclide isolation in radioactive waste management are discussed. We could not prepare CeSiO/sub 4/ by conventional ceramic techniques, hydrothermal treatment at 700/sup 0/C, or precipitation. The use of cerium as a substitute for the actinides is also considered. Unit cell constants for REPO/sub 4/ (RE = La to Gd) have been redetermined. Nine-fold coordinated ionic radii for Pu/sup 3 +/, Am/sup 3 +/, and Cm/sup 3 +/ in the monazite structure type have been calculated.
Research Organization:
Rockwell International Corp., Canoga Park, CA (USA). Energy Systems Group
DOE Contract Number:
AC09-79ET41900
OSTI ID:
6323579
Report Number(s):
DOE/ET/41900-7; ESG-DOE-13351; ON: DE81028554
Country of Publication:
United States
Language:
English

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ACTINIDE COMPOUNDS
ACTINIDES
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
AMERICIUM
CALCIUM COMPOUNDS
CALCIUM PHOSPHATES
CATIONS
CERIUM
CERIUM COMPOUNDS
CERIUM PHOSPHATES
CESIUM COMPOUNDS
CESIUM SILICATES
CHARGED PARTICLES
CRYSTAL STRUCTURE
CURIUM
DATA
DISPERSIONS
ELEMENTS
EUROPIUM COMPOUNDS
EUROPIUM PHOSPHATES
EXPERIMENTAL DATA
GADOLINIUM COMPOUNDS
GADOLINIUM PHOSPHATES
INFORMATION
IONS
LANTHANUM COMPOUNDS
LANTHANUM PHOSPHATES
LATTICE PARAMETERS
MATERIALS
METALS
MINERALS
MIXTURES
MONAZITES
NEODYMIUM COMPOUNDS
NEODYMIUM PHOSPHATES
NUMERICAL DATA
OXYGEN COMPOUNDS
PHASE STUDIES
PHOSPHATES
PHOSPHORUS COMPOUNDS
PLUTONIUM
PRASEODYMIUM COMPOUNDS
PRASEODYMIUM PHOSPHATES
RADIOACTIVE MATERIALS
RADIOACTIVE MINERALS
RARE EARTH COMPOUNDS
RARE EARTHS
SAMARIUM COMPOUNDS
SAMARIUM PHOSPHATES
SILICATES
SILICON COMPOUNDS
SOLID SOLUTIONS
SOLUTIONS
SYNTHESIS
THORIUM COMPOUNDS
THORIUM MINERALS
THORIUM PHOSPHATES
TRANSPLUTONIUM ELEMENTS
TRANSURANIUM ELEMENTS
URANIUM COMPOUNDS
URANIUM PHOSPHATES
VERY HIGH TEMPERATURE