Synthesis and study of a new mixed-layered compound GeBi3Te4 belonging to the nBi2–mGeBi2Te4 homologous series

Abstract

In light of the structural properties of tetradymite-like layered chalcogenide compounds, the mixed-layered compound GeBi3Te4 was predicted and synthesized for the first time, which belongs to the nBi2–mGeBi2Te4 homologous series in the Ge-Te-Bi system. A polycrystal of a new phase was synthesized, and its single crystal was grown by the Bridgman–Stockbarger method. The obtained samples were investigated by differential thermal analysis (DTA) and powder X-ray diffraction (XRD). It was found that the compound melts peritectically at 563 C and has a rhombohedral lattice-type structure with the following lattice parameters: a = 4.3625 (5) Å, c = 31.381 (2) Å (sp. gr R3m). The crystal structure of the layered van der Waals compound GeBi3Te4 consists of a repetition of seven-layer GeBi2Te4 packets and two-layer Bi packets in the form of -7- 2-7-7-2-7-7-2-7- which differ from the previously discovered GeBi4Te4 phase, which consists of unit cells from only one seven-layer packet. The discovery of a new mixed-layered compound indicates the possibility of the formation of similar compounds in AIV–BV–Te (AIV = Ge, Sn, Pb; BV = Sb, Bi) systems.