LAUSR

Abstract The hydrogenation properties of binary palladium-rich intermetallic compounds MPd3 (M = Pb, Bi) were studied by X-ray powder diffraction and by in situ thermal analysis (DSC) under hydrogen pressure. Ex situ neutron powder diffraction reveals deuterium filled [Pd6] octahedral voids in a cubic anti-perovskite type structure for PbPd3D0.13(1) (Pm 3 ¯ m, a = 404.033(6) pm, deuterium occupation = 0.13(1)) and in a ZrAl3 type for BiPd3D0.19(1) and BiPd3D0.23(1) (I4/mmm, a = 404.72(1) pm, c = 1662.64(6) pm, z(Bi) = 0.1320(1), z(Pd3) = 0.3797(2), deuterium occupation = 0.46(1)). In situ neutron diffraction (using deuterium) reveals full reversibility of the hydrogenation and dehydrogenation reaction for BiPd3 without intermediate phases and variable hydrogen content in the hydride. The relation of the crystal structures of BiPd3 (akin to double-hexagonal close packing) and its hydride with filled ZrAl3 type (ordered superstructure of cubic close packing) is discussed in view of a possible reaction mechanism.