PREPARATION AND STRUCTURE OF MONODISPERSE D SUPERFINE PARTICLES OF COMPLEX RARE-EARTH-OXIDES AND OXYSULFIDES

Monodispersed fine spherical particles (similar to 100 nm) of complex rare earth hydroxycarbonates are prepared by hydrolizing mixed rare ea rth nitrates solution at elevated temperature in the presence of urea. By calcining the hydroxycarbonates at moderate temperature, complex r are earth sesquioxides (similar to 70 nm) of C-type can be obtained. T he mechanism of the decomposition of hydroxycarbonate at different tem peratures have been verified to proceed through monoxydicarbonate diox ymonocarbonate to sesquioxide of body-centered structure by DTA, TGA, XRD and HREM. The experimental EDP diagrams of complex rare earth sesq uioxides have been identified with those of calculated C-type structur e. Complex rare earth oxysulfides of hexagonal structure can be prepar ed by firing a blend of complex rare earth hydroxycarbonate; S, Na2CO3 and KH2PO4 at 1000 degrees C.