ONE-DIMENSIONALLY MODULATED QUASI-CRYSTAL PHASE RELATED TO ICOSAHEDRAL AL-MN-PD

A new one-dimensionally modulated quasicrystal phase related to the ic osahedral Al-Mn-Pd quasicrystal is described from an alloy with compos ition Al69.8Mn8.3Pd21.9 annealed at temperatures between 550 and 715 d egrees C and subsequently quenched in water. Systematic tilting experi ments reveal that this phase is an icosahedral quasicrystal with a mod ulation along one of its threefold symmetry axes. It therefore has a t rigonal-symmetric Fourier spectrum and a modulation period along the u nique threefold axis which corresponds to 15.7 nm. This long-range ord ered phase is related to the usual F-type icosahedral quasicrystal as well as to the F2 icosahedral quasicrystal which has a P-type icosahed ral lattice.