Effect of atom substitution on the low-temperature phase transitions in Cd- and Zn-based 1/1 cubic approximants

Abstract

Effect of atom substitution on the low-temperature phase transitions in binary Cd6Ca and Zn6Sc 1/1 cubic approximants were investigated by means of electrical resistivity and X-ray diffraction. By adding thirdelements such as Yb, Cu and Fe to the binary approximants, it is concluded that Yb is substituted to the icosahedron site in both Cd6Ca and Zn6Sc, and Cu and Fe are substituted to the Zn sites in Zn 6Sc. Upon the substitutions of the third elements, the temperature of the resistivity anomaly decreases without an exception and the anomaly disappears above a certain level of substitutions. Moreover, it is found that the chemical disorder introduced in the 2nd shell of the icosahedral cluster plays a crucial role in the suppression of the ordering of the Zn tetrahedron. On the other hand, the chemical disorder introduced in the 3rd icosahedron shell affects the transition temperature (Tc) rather weakly. Finally, the variation of Tc has been found to depend on the difference of the atomic radius between the host and the guest elements and the distortion of the outer shells is considered to be mainly responsible for the suppression of the ordering of the tetrahedra. © by Oldenbourg Wissenschaftsverlag.