The structure of Co₂Al₉

Phase equilibria in the system Al–Co–Si

“…Given the radii of Al and Si (atomic radius: r(Al)Z1.43 Å , r(Si)Z 1.17 Å ; covalent radius (r(Al)Z1.25 Å , r(Si)Z1.17 Å ) [23], the substitution of Al by Si will be accompanied by a decrease of unit cell volume and vice versa. For monoclinic Co 2 Al 9 the lattice parameters were found to range from aZ10.149(6)-10.118(1) Å , bZ6.290(5)-6.2299(6) Å , cZ8.5565(5) -8.5508(8) Å and bZ 142.40(5)-142.434(4)8 between the binary compound Co 2 Al 9 [7] and the solubility limit at 6.6 at.% Si corresponding to the formula Co 2 Al 8.27 Si 0.73 . The volume change from 333.28 to 328.60 Å 3 is consistent with Al/Si Among binary Co-Si phases, cubic CoSi was found to form the most extended solid solution with Al.…”

“…In the binary Al-Co system seven different phases have been found to exist. These compounds are Co 2 Al 9 (Pearson symbol mP22, space group P2 1 /c, Co 2 Al 9 -type) [7], a bundle of three different phases at Co 4 Al 13 stoichiometry: o-Co 4 Al 13 (oP102, Pmn2 1 , o-Co 4 Al 13 -type) [8], m-Co 4 Al 13 (mC102-7.2, Cm, m-Co 4 Al 13 -type) [9,10] and h-Co 4 Al 13 (also designated as Y-phase) (mC34, C2/m, Os 4 Al 13 -type) [5]. The compound CoAl 3 (also designated as Z-phase or t 2 -Co 4 Al 13 ) is reported to be decagonal quasicrystalline and different approximant models have been given for the compound [11,12].…”

Structure and transformation behaviour of a rapidly solidified Al–Y–Ni–Co–Pd alloy

“…11(b). The subsequent exothermic DSC peaks correspond to precipitation of an orthorhombic Cmcm Al 4 YNi [36] and monoclinic P2 1 /a Al 9 Co 2 [37] phases ( Fig. 11(c)).…”

The Co2Al9 Structure Type Revisited.

“…Four representatives of the Co 2 Al 9 structure type [1] have been found exclusively among aluminides and gallides of the cobalt group transition metals: Rh 2 Al 9 , Ir 2 Al 9 [2], Rh 2 Ga 9 and Ir 2 Ga 9 [3]. Except for Co 2 Al 9 , none of the structures have previously been refined from single crystal or powder diffraction data.…”