Fu Qiang Huang

Syntheses and structures of the quaternary alkali-metal bismuth coinage-metal chalcogenides K3Bi5Cu2S10, CsBi2CuS4, RbBi2.66CuSe5, and CsBiAg2S3

Abstract The four compounds K 3 Bi 5 Cu 2 S 10 , CsBi 2 CuS 4 , RbBi 2.66 CuSe 5 , and CsBiAg 2 S 3 were synthesized at 873 K by reactions of the elements in the reactive fluxes of A 2 Q 3 (A=K, Rb, Cs; Q=S, Se). All crystallographic data were collected at 153 K. K 3 Bi 5 Cu 2 S 10 crystallizes in the Rb 3 Bi 5 Cu 2 S 10 structure type in space group Pnnm of the orthorhombic system with two formula units in a cell of dimensions a =14.173(2) A, b =17.690(2) A, c =4.0362(5) A; CsBi 2 CuS 4 crystallizes as a racemic twin in space group Cmc2 1 of the orthorhombic system with four formula units in a cell of dimensions a =4.0730(6) A, b =14.212(2) A, c =14.568(2) A; RbBi 2.66 CuSe 5 crystallizes in a new structure type in space group Cmcm of the orthorhombic system with four formula units in a cell of dimensions a =4.1961(9) A, b =14.420(3) A, c =18.266(4) A; CsBiAg 2 S 3 crystallizes in a new structure type in space group P2 1 /c of the monoclinic system with four formula units in a cell of dimensions a =13.3523(14) A, b =8.1052(8) A, c =6.9162(7) A, β =99.766(2)°. K 3 Bi 5 Cu 2 S 10 , CsBi 2 CuS 4 , and RbBi 2.66 CuSe 5 are related; they are all tunnel structures with the A atoms located in tunnels formed by BiQ 6 octahedra and CuQ 4 tetrahedra. CsBiAg 2 S 3 is composed of two-dimensional ∞ 2 [BiAg 2 S 3 1− ] layers separated by the Cs atoms. The ∞ 2 [BiAg 2 S 3 1− ] layer is built from BiS 6 octahedra, linear AgS 2 groups, and AgS 4 tetrahedra.

Oxide Addition to a Reactive Polysulfide Flux: Synthesis of K4Ba[Ti6OS20] Containing Isolated [Ti6OS8(S2)6]6− Clusters

The zero-dimensional cluster compound K4 Ba[Ti6 OS8 (S2 )6 ] has been synthesized from a reactive flux similar to that of K2 Sn and Ti used in the synthesis of the one-dimensional compound K4 Ti3 S14 , but augmented by the deliberate introduction of TiO2 . The picture shows the structure of the [Ti6 OS8 (S2 )6 ]6- ion.

Syntheses, crystal structures, and physical properties of La 5Cu6O4S7 and La5Cu 6.33O4S7

Single crystal and bulk powder samples of the quaternary lanthanum copper oxysulfides La5Cu6.33O4S7 and La5Cu6O4S7 have been prepared by means of high-temperature sealed-tube reactions and spark plasma sintering, respectively. In the structure of La 5Cu6.33O4S7, Cu atoms tie together the fluorite-like (2)infinity[La5O4S(5+)] and antifluorite-like (2) infinity[Cu6S6(5-)] layers of La5Cu6O4S7. The optical band gap, E g, of 2.0 eV was deduced from both diffuse reflectance spectra on a bulk sample of La5Cu6O4S7 and for the (010) crystal face of a La 5Cu6.33O4S7 single crystal. Transport measurements at 298 K on a bulk sample of La 5Cu 6O 4S 7 indicated p-type metallic electrical conduction with sigma electrical =2.18 S cm(-1), whereas measurements on a La 5Cu6.33O4S7 single crystal led to sigma electrical =4.5 10(-3) S cm(-1) along [100] and to semiconducting behavior. In going from La 5Cu6O4S7 to La5Cu6.33O4S7, the disruption of the (2)infinity[Cu6S6(5-)] layer and the decrease in the overall Cu(2+)(3d(9)) concentration lead to a significant decrease in the electrical conductivity.

Syntheses, crystal structures, and physical properties of La 5 Cu 6 O 4 S 7 and La 5 Cu 6.33 O 4 S 7

Single crystal and bulk powder samples of the quaternary lanthanum copper oxysulfides La5Cu6.33O4S7 and La5Cu6O4S7 have been prepared by means of high-temperature sealed-tube reactions and spark plasma sintering, respectively. In the structure of La 5Cu6.33O4S7, Cu atoms tie together the fluorite-like (2)infinity[La5O4S(5+)] and antifluorite-like (2) infinity[Cu6S6(5-)] layers of La5Cu6O4S7. The optical band gap, E g, of 2.0 eV was deduced from both diffuse reflectance spectra on a bulk sample of La5Cu6O4S7 and for the (010) crystal face of a La 5Cu6.33O4S7 single crystal. Transport measurements at 298 K on a bulk sample of La 5Cu 6O 4S 7 indicated p-type metallic electrical conduction with sigma electrical =2.18 S cm(-1), whereas measurements on a La 5Cu6.33O4S7 single crystal led to sigma electrical =4.5 10(-3) S cm(-1) along [100] and to semiconducting behavior. In going from La 5Cu6O4S7 to La5Cu6.33O4S7, the disruption of the (2)infinity[Cu6S6(5-)] layer and the decrease in the overall Cu(2+)(3d(9)) concentration lead to a significant decrease in the electrical conductivity.