Two new quaternary copper bismuth sulfide halides: CuBi2S3Cl and CuBi2S3Br as candidates for copper ion conductivity

Abstract

Abstract Two new copper bismuth sulfide halides, CuBi2S3Cl and CuBi2S3Br, were synthesized by a two-step process of ball milling followed by annealing. Both compounds are obtained as dark grey powders and crystallize in the monoclinic space group C2/m with lattice parameters a = 12.9458(11) Å, b = 3.9845(3) Å, c = 9.1024(8) Å and β = 91.150(3)° for the sulfide chloride and a = 13.3498(8) Å, b = 4.1092(2) Å, c = 9.4173(6) Å and β = 90.322(4)° for the sulfide bromide. Also known for related compounds, the copper atoms are strongly disordered. Quantum-chemical calculations suggest that modelling the structure with fixed copper positions does not satisfactorily describe all structural features, which insinuates copper ion mobility at elevated temperatures.