Eu7Ga6Sb8: A Zintl phase with Ga-Ga bonds and polymeric gallium antimonide chains

Abstract

The Zintl phase Eu7Ga6Sb8 was obtained from a direct element combination reaction at 900°C. It crystallizes in the orthorhombic space group Pbca (No. 61) with a=15.6470(17)Å, b=17.2876(19)Å, c=17.9200(19)Å, and Z=8. In Eu7Ga 6Sb8, the anionic framework forms infinite chains of [Ga6Sb8]14- which are arranged side by side to make a sheet-like arrangement but without linking. The sheets of chains are separated by Eu2+ atoms and also within the sheet, Eu2+ atoms fill the spaces between two chains. The chain is made up of homoatomic tetramers (Ga4)6+ and dimers (Ga2)4+ connected by Sb atoms. The compound is a narrow band-gap semiconductor with Eg∼0.6eV and satisfies the classical Zintl concept. Extended Hückel band structure calculations confirm that the material is a semiconductor and suggest that the structure is stabilized by strong Ga-Ga covalent bonding interactions. Magnetic susceptibility measurements for Eu 7Ga6Sb8 show that the Eu atoms are divalent and the compound has an antiferromagnetic transition at 9K. © 2004 Elsevier Inc. All rights reserved.