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 established. The addition of C expands the lattice parameters of pure Gd, indicating that C dissolves in Gd, but the solid solubility of C is less than 2 at.% below 600 degrees C. Below 600 degrees C the 'Gd2C' phase appears to exist as a line compound, but exhibits a narrow solid solution region above this temperature. This phase is slightly C deficient, i.e., Gd2C1-x, where x=0.015 [Gd2C0.985]. 'Gd2C' has the rhombohedral C19, CdCl2-type structure with a=6.29 Angstrom and alpha=33.70 degrees. The Gd-C alloys are quite reactive in moist air, forming gaseous hydrocarbons and a white powder which flakes off of the metallic ingots, and must be handled in glove boxes. Magnetic measurements indicated 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.