SOME OBSERVATIONS ON THE GD-RICH SIDE OF THE GD-C SYSTEM

The phase relationships at the Gd-rich end of the Gd-C system were est ablished. The addition of C expands the lattice parameters of pure Gd, indicating that C dissolves in Gd, but the solid solubility of C is l ess than 2 at.% below 600 degrees C. Below 600 degrees C the 'Gd2C' ph ase appears to exist as a line compound, but exhibits a narrow solid s olution region above this temperature. This phase is slightly C defici ent, i.e., Gd2C1-x, where x=0.015 [Gd2C0.985]. 'Gd2C' has the rhombohe dral C19, CdCl2-type structure with a=6.29 Angstrom and alpha=33.70 de grees. The Gd-C alloys are quite reactive in moist air, forming gaseou s hydrocarbons and a white powder which flakes off of the metallic ing ots, and must be handled in glove boxes. Magnetic measurements indicat ed that 'Gd2C' orders ferromagnetically at 350 degrees C. This is the highest known magnetic ordering temperature for any binary lanthanide compound which does not contain Fe or Co. (C) 1997 Elsevier Science S. A.