NEW ORTHORHOMBIC APPROXIMANTS OF THE AL70CO15NI10TB5 DECAGONAL QUASI-CRYSTAL

Three new orthorhombic approximants, C1, C2, and C3, have been found in the Al70Co15Ni10Tb5 decagonal quasicrystal, which was prepared by a method of quenching from the melt under a high static pressure. The lattice parameters of these orthorhombic phases are as follows: C1, a = 2.28 nm, b = 1.60 nm and c = 5.46 nm (B type); C2 a = 6.1 nm, b = 0.4 nm and c = 8.4 nm (P type); C3, a = 6.1 nm, b = 0.4 nm and c = 8.4 nm (B type). The strong diffraction spots in the electron diffraction patterns of these phases show the same intensity modulation as those of the decagonal quasicrystal, implying a close relationship between them.