Crystal chemistry of the G-phases in the systems Ti–{Fe, Co, Ni}–Al with a novel filled variant of the Th6Mn23-type

The crystal structures of the compounds Ti6M7Al17 with M=Fe,Co,Ni have been investigated by X-ray powder and single crystal, neutron powder and electron diffraction. These compounds crystallize with a new filled variant of the Mg6Cu16Si7-type (space group Fm3̄m). A close structural relation is encountered for the series of crystal structures: Th6Mn16Mn7?, Mg6Cu16Si7?, Sc6Sc16Ir7Ir, Zr6Zn16Zn7Si, Ti6Al16M7Al, and Ti6Ni16Si7Si. Electrical resistivity of the Fe, Co-based compounds is typical metallic and temperature dependence follows the Bloch Grüneisen relation with a Debye temperature of about 300 K. No hydrogen was found to be absorbed in the Fe-, and Co-based compounds at room temperature under a H2 pressure of 5 MPa.