  Starting from the Zn17Sc3 cubic approximant, new quasicrystal alloys were
searched by replacement of Zn with transition elements, T. In the cases of
T=Mn, Fe, Co and Ni, new icosahedral quasicrystals are formed in as-cast alloys
as major phases at the alloy compositions of Zn75T10Sc15. All these
quasicrystals belong to a primitive type, and have 6-dimensional lattice
parameters, a6D, ranging from 7.044 to 7.107 A. They have the valence electron
concentrations, e/a, ranging from 2.01 to 2.14, and almost the same ratios
between the edge-length of the Penrose tile, aR, and the averaged atomic
diameter d: aR/d~1.75. Moreover other Zn- and Cd-based quasicrystals including
the same type of atomic cluster, Tsai-type cluster, also have the same values
of e/a~2.1 and aR/d~1.75. The equality in e/a indicates that the Hume-Rothery
mechanism plays an important role for the formation of these quasicrystals.
