The solid solutions RETi2Al20−x Ga x (0 ≤ x ≤ 10) with RE = Eu, Gd, Tb, Dy and Yb − first gallides with CeCr2Al20-type structure

Abstract The CeCr 2 Al 20 -type aluminides RE Ti 2 Al 20 ( RE = Eu, Gd, Tb, Dy and Yb), space group F d 3 ‾ m $Fd\overline{3}m$ , show the formation of solid solutions RE Ti 2 Al 20− x Ga x with gallium in the ranges 0 ≤ x ≤ 10. Polycrystalline samples were prepared from the elements in alumina crucibles or directly via arc-melting followed by annealing in order to increase crystallinity. The structures of six single crystals were refined from single crystal X-ray diffractometer data for determining the precise occupancy parameters of the aluminum and gallium atoms. The solubility limit of gallium was found at around x ≈ 10. The RE Ti 2 Al 20− x Ga x structures show a MgCu 2 -related substructure of the rare earth and titanium atoms. The Al/Ga atoms then form Frank-Kasper type polyhedra around the RE and Ti atoms, i. e., RE @(Al/Ga) 16 and Ti@(Al/Ga 12 ). These are the basic building units of the RE Ti 2 Al 20− x Ga x structures. Temperature-dependent magnetic susceptibility studies show Pauli paramagnetic behavior for the YbTi 2 Al 10 Ga 10 sample, i. e., a stable divalent ytterbium ground state.