Copper Bismuth Chalcogenide Halogenides with Extensively Disordered and Mobile Copper(I) Cations

A new family of quaternary phases with the general sum formula Cu 3+ δ Bi 5– δ Se 8–2 δ X 2+2 δ ( X = Cl, Br) was discovered by slow cooling of high temperature melts. Cu 3.58(1) Bi 4.42(1) Se 6.84(2) Cl 3.16(2) ( δ = 0.58) and Cu 4.52(1) Bi 3.48(1) Se 4.96(2) Br 5.04(2) ( δ = 1.52) crystallize isostructural in the orthorhombic space group type Pnnm with a = 1332.3(1)/1340.2(3) pm, b = 1683.7(2)/1717.2(1) pm, and c = 406.2(1)/407.1(2) pm. The new structure type resembles in some aspects the hollandite as well as the pavonite type. A framework of face‐ and edge‐sharing anion polyhedra around Bi 3+ cations hosts Cu + cations. The characteristic motif is an infinite band of polyhedra that has the width of five polyhedra, with three octahedra being enclosed by capped trigonal prisms. The octahedrally coordinated Bi 3+ cations are partially substituted by Cu + (in octahedra faces), while Se 2– anions are replaced by X – . The sulfide iodide Cu 3.33(2) Bi 2 S 3.33(2) I 2.67(2) crystallizes in the monoclinic space group C 2/ m with a = 2803.6(9) pm, b = 409.9(1) pm, c = 1058.0(3) pm, and β = 110.68(2)°. Double strands of face‐sharing [BiS 1/1 S 2/2 I 4/4 ] as well as [BiS 3/3 I 2/2 (S 0.33 /I 0.67 ) 2/2 ] polyhedra run along [010]. In between them, the Cu + cations are spread over numerous closely spaced sites. They define a ladder‐shaped continuous path for ion conduction along [010].