|Source||United States Department of Energy Office of Scientific and Technical Information|
|Subject Keyword||GEOLOGY, MINERALOGY, AND METEOROLOGY ♦ AGE ESTIMATION ♦ CALCIUM FLUORIDES ♦ CATIONS ♦ CRYSTALS ♦ DEFECTS ♦ DEFORMATION ♦ FLUORITE ♦ HEAT TREATMENTS ♦ LATTICES ♦ LEAD ♦ OXIDATION ♦ OXYGEN ♦ PHASE DIAGRAMS ♦ QUANTITY RATIO ♦ THORIUM ORES ♦ URANINITES ♦ URANIUM ♦ URANIUM DIOXIDE ♦ VOLUME|
|Abstract||A study was made of the effect of heat treatment on reduction of cell size of gamma uraninite to correspond to age values consistent with those of the a1pha type. A number of specimens of uraninite from Bisundni and Gaya and thorianite from Ceylon was used for the study. Data are tabulated on the shrinkage of the cell size of uranium dioxide as followed by a close doubling of the higher-angle diffraction lines. The oxidation of uraninite out of contact with oxygen suggests that in the oxygen-rich lattice of natural uraninite the excess of oxygen occupies the available interstitial positions in six-fold coordination with uranium and the shrinkage of cell size implies simultaneous replacement of U/sup 4+/ cations by the U/sup 6+/ cations, that is, the substitution of cations of smaller ionic radii and higher charge is preceded by readjustment of interstitial anions in the fluorite-type lattice. The progressive reduction of cell size of uranium dioxide due to the substitution of Pb/sup 4+/ for U/sup 4+/ within the lattice with time is considered to be negligible. (C.H.)|
|Learning Resource Type||Article|
|Publisher Department||Geological Survey of India, Calcutta|
|Organization||Geological Survey of India, Calcutta|
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