Zr₄CuSb₇ – A PbFCl-related Polyantimonide, and Structure Relations of Zirconium-Transition Metal Polyantimonides

Abstract

Single crystals of tetrazirconium copper heptaantimonide were obtained by arc-melting and annealing from the elements in ideal ratios including a 10% excess of Sb. The excess of Sb is needed to compensate for the evaporation loss during arc-melting synthesis. Zr4CuSb7 crystallizes tetragonally, space group P4bm (no. 100) as a racemic twin. It adopts a unique structure that can be regarded as a composite of a PbClF unit and a layered, partially copper-substituted polyantimonide substructure. Zr4CuSb7 represents a filling and substitution variant of the Hf5Sb9 structure type. The copper atoms fill voids and partially replace antimony atoms in the 4.82 Sb net of the Hf5Sb9 polyantimonide substructure to form a distorted 44 net in Zr4CuSb7. Structure relations to known zirconium-transition metal polyantimonides are given, and new structures are predicted based on these relations.