The ternary system: silicon-titanium-uranium

Phase equilibria in the system Si-Ti-U were established at 1000 deg. C by optical microscopy, EMPA and X-ray diffraction. Two ternary compounds were observed and were characterised by X-ray powder data refinement: (1) stoichiometric U2Ti3Si4 (U2Mo3Si4-type) with a small homogeneity region of about 3 at.% exchange U/Ti and (2) U2-xTi3+xSi4 (Zr5Si4-type) extending at 1000 deg. C for 0.7<x<1.3. Mutual solubility of U-silicides and Ti-silicides was found to be below about 1 at.%. The Ti,U-rich part of the diagram was also investigated at 850 deg. C establishing the tie-lines to the low temperature compounds U2Ti and U3Si. U2Ti3Si4 is weakly paramagnetic following a Curie-Weiss law above 50 K with μeff.=2.67 μB/U, ΘP=-150 K and χ0=1.45x10-3 emu/mol (18.2x10-9 m3/mol)