Timothy J. McCarthy

Synthesis in molten alkali metal polythiophosphate fluxes. The new quaternary bismuth and antimony thiophosphates ABiP2S7 (A = K, Rb), A3M(PS4)2 (A = K, Rb, Cs; M = Sb, Bi), Cs3Bi2(PS4)3, and Na0.16 Bi1.28P2S6

Abstract We used the molten alkali metal polychalcogenide flux method to prepare the new compounds ABiP 2 S 7 (A = K, Rb), A 3 M(PS 4 ) 2 (A = K, Rb, Cs; M = Sb, Bi), Cs 3 Bi 2 (PS 4 ) 3 , and Na 0.16 Bi 1.28 P 2 S 6 . KBiP 2 S 7 crystallizes in the monoclinic space group P 2 1 / c with a = 9.500(3) A , b = 12.303(4) A , c = 9.097(3) A , β = 90.59(3)°, V = 1063 A 3 , at 23°C. D calc = 3.34 g cm −3 , μ = 184.85 cm −1 , 2 θ max = 50° Mo Kα. Data with I > 3 σ ( I ) 1672, R / Rw (%) = 2.8/3.1. K 3 Bi(PS 4 ) 2 crystallizes in the orthorhombic space group P 2 1 2 1 2 1 with a = 23.894(8)(3)A, b = 6.799(3)A, c = 9.049(2)A, V = 1470A 3 , at −60°C. D calc = 2.91 g cm −3 , μ = 140.8 cm −1 , 2 θ max = 50°. Data with I > 3 σ ( I ) 1745, R / Rw (%) = 5.5/6.0. Cs 3 Bi 2 (PS 4 ) 3 crystallizes in the monoclinic space group P 2 1 / c with a = 18.091(5) A , b = 6.791(2) A , c = 18.723(3) A , β = 97.95(2)°, V = 2278 A 3 , at 23°C. D calc = 3.77 g cm −3 , μ = 213.3 cm −1 , 2 θ max = 50°. Data with I > 3 σ ( I ) 2623, R / Rw (%) = 7.0/9.0. Na 0.16 Bi 1.28 P 2 S 6 crystallizes in the monoclinic space group P 2 1 / n with a = 6.554(2) A , b = 7.297(2) A , c = 9.371(1) A , β = 92.04(2)°, V = 447.8 A 3 , at 23°C. D calc = 3.73 g cm −3 , μ = 236.2 cm −1 , 2 θ max = 50°. Data with I > 3 σ ( I ) 892, R / Rw (%) = 7.7/8.5. The structural diversity in this family of compounds ranges from the one-dimensional non-centrosymmetric chains of A 3 M(PS 4 ) 2 and the layered compounds, ABiP 2 S 7 and Cs 3 Bi 2 (PS 4 ) 2 , to the dense three-dimensional framework of Na 0.16 Bi 1.28 P 2 S 6 . KBiP 2 S 7 is a layered solid with a complex new structure type, where corrugated layers are separated by eight-coordinate K + ions. It contains a [P 2 S 7 ] 4− ligand in a complicated coordination mode. The structure of K 3 Bi(PS 4 ) 2 is assembled from one-dimensional, helical [Bi(PS 4 ) 2 ] n 3 n − chains running along the crystallographic b -axis. The chain structure features two interesting binding modes for a tetrahedral [PS 4 ] 3− ligand. The structure of Cs 3 Bi 2 (PS 4 ) 3 has layers containing the same one-dimensional helical chains observed in K 3 Bi(PS 4 ) 2 . However, the PS 4 unit acts as a bridge to a Bi 2 (PS 4 ) 2 dimeric unit. This unit is linked to another chain via a second bridging PS 4 ligand to form sheets that are parallel to the [101] crystallographic plane. The structure of Na 0.16 Bi 1.28 P 2 S 6 is three dimensional but consists of layers of P 2 S 6 groups in the a-b plane separated by a single layer of Bi 3+ ions. The ethane-like [P 2 S 6 ] 4− ligand chelates to eight Bi atoms in a very convoluted fashion. Positional disorder was found between Na and Bi ions in one crystallographic site. Their synthesis, structural characterization, optical absorption and thermal properties are reported.

Ternary bismuth chalcogenides for thermoelectric applications. Synthesis and charge transport properties of new compounds in the K-Bi-S system

Group 15 chalcogenide compounds have received considerable attention, due to their potential application as thermoelectric cooling materials. KBi{sub 6.33}S{sub 10} and K{sub 2}Bi{sub 8}S{sub 13} were synthesized by the direct combination of K{sub 2}S/Bi{sub 2}S{sub 3} at high temperature (> 700 C). The reaction of K{sub 2}S/3.3Bi{sub 2}S{sub 3} at 800 C revealed the presence of a new ternary sulfide KBi{sub 6.33}S{sub 10} (1) (92% yield). The structure consists of blocks of Bi{sub 2}Te{sub 3} and CdI{sub 2}-type units that are connected to form a three-dimensional network with K{sup +} ions located in the channels that run along the b-axis. The same reaction but with a different ratio, at 750 C, gave the new ternary sulfide K{sub 2}Bi{sub 8}S{sub 13} (2) (94% yield). The structure of the shiny rod-like crystals is closely related to that of 1. As in 1, it also consists of Bi{sub 2}Te{sub 3} and CdI{sub 2}-type fragments that connect to form K{sup +}-filled channels. The two potassium atoms and one bismuth atom are disordered over three sites. Some preliminary electrical and optical properties of these materials are discussed.

Coordination chemistry of [P2Se6]4– in molten fluxes. Isolation of the structurally complex KMP2Se6(M = Sb, Bi)

The layered compounds, KMP2Se6(M = Sb, Bi), have been prepared by the reaction of Bi(Sb) with a molten alkali-metal polyselenophosphate flux.