MICROSCOPIC INVESTIGATIONS OF THE THMN12-TYPE URANIUM TERNARIES

The structure of the ThMn12-type uranium ternaries (UNi10Si2, UFe0.5Ni 2 and UCo0.5Ni9.5Si2) was studied by high resolution transmission elec tron microscopy and electron diffraction. The general appearance of al l the samples was similar, i.e. large individual crystals (a few micro metres) and aggregates of very fine, randomly oriented crystallites (1 0-30 nm) were observed. In addition, especially for the Fe-contaiming sample, another, distinct phase comprising very fine crystallites embe dded in an amorphous matrix could be seen. The main constituent of all the samples was a tetragonal I4/mmm phase, isomorphous with ThMn12, w ith lattice parameters a=0.82 nm and c=0.47 nm. In addition, individua l crystallites of a cubic phase (a=0.55 nm), probably UO2, and another , unidentified phase exhibiting unusual contrast variations were found .