Expanding multiple anion superlattice chemistry: Synthesis, structure and properties of Bi4O4SeBr2 and Bi6O6Se2Cl2

Abstract

The synthesis, structure, and properties of the three-anion superlattice materials Bi4O4SeBr2 and Bi6O6Se2Cl2 are reported. These materials crystallise in structures that form part of a homologous series of compounds comprised of stackings of BiOCl- and Bi2O2Se-like units. Bi4O4SeBr2 is analogous to Bi4O4Se2Cl2, whereas Bi6O6Se2Cl2 contains an additional Bi2O2Se layer that produces off-centred anions. The band gaps of both materials are indirect, with Eg ​= ​1.15(5) eV, and the materials behave as doped semiconductors with very low thermal conductivities. These materials expand the synthetic scope of multiple anion superlattice materials and, with optimisation, may also be platforms for future thermoelectric materials.