Yb-Zn-Al ternary system: CaCu5-type derived compounds in the zinc-rich corner

摘要

As part of a study of the Yb-Zn-Al system, this first article reports the synthesis and crystal structure of four compounds. The crystal structures were determined by single crystal diffractometer data for three of them: Yb3.36Zn30.94Al4.34, hexagonal, P6/mmm, a = 9.061(2) angstrom, c = 8.878(2) angstrom, Z = 1, wR(2) = 0.055, with a structure derived from the SmZn11 similar to type; (Yb6.4ZnAl3.4)-Al-46.8, hexagonal, P6/mmm, a = 9.096(3) angstrom, c = 13.178(5) angstrom, Z = 1, wR(2) = 0.060, with its own structure; Yb12.4Zn96.8Al4.4, hexagonal, P6(3)/mmc, a = 9.068(2) angstrom, c = 26.369(8) Z = 1, wR(2) = 0.088, with a structure derived from the U2Zn17 type. The structure of Yb3Zn17.7Al4.3, tetragonal, I4(1)/amd, a = 8.920(1) angstrom, c = 21.294(1) angstrom, Z = 4, related to the Ce3Zn22 type, was refined from powder data by the Rietveld method. The four structures belong to the same family, derived from the CaCu5 type by replacing totally or partially some Ca atoms with dumbbells of partner elements. All the structures show no order for the aluminium atoms, but they preferentially occupy the dumbbells sharing the sites with zinc. (C) 2006 Elsevier Inc. All rights reserved.