A Study on New Orthorhombic Approximants of the Al70Co15Tb5Ni10 Decagonal Quasi-crystal

Two new orthorhombic approximants with the largest until cell observed up to now were found in the Al70Co15Tb5Ni10 decagonal quasi-crystal, which were prepared by quenching (102 ℃/s) the melt state (1 700 ℃) under high static pressure (7.0 GPa). The lattice parameters of the orthorhombic approximant are the same (a=6.1 nm, b=0.4 nm, c=8.4 nm), but the structure of the first phase is P-type and that of the second phase is a B-type. Their structures and lattice parameters are in accordance with that of the present theoretical predictions.