Kwasi Mitchell

Synthesis, crystal structure, and optical properties of CeMn0.5OSe

The new quaternary selenide CeMn0.5OSe has been synthesized by the reaction of Ce, Mn, Se, and SeO2 at 1223 K. This compound crystallizes in space group P4/nmm of the tetragonal system with two formula units in a cell of dimensions at 153 K of a ¼ 4:0260ð7Þ A ˚ , c ¼ 9:107ð2Þ A ˚ . CeMn0.5OSe has the LaAgOS structure type. It is built from [CeO] fluorite-like layers where Ce4O tetrahedra share Ce–Ce edges that alternate with [MnSe] anti-fluorite like layers along [001]. An optical band gap of 2.01 eV has been derived from absorption measurements on the (100) crystal face of a CeMn0.5OSe single crystal. r 2003 Elsevier Inc. All rights reserved.

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.