Synthesis, crystal structure and transport properties of the cluster compounds Tl2Mo15S19 and Ag3Tl2Mo15S19
Résumé
We report the syntheses and crystal structures of the cluster compounds Tl2Mo15S19 and Ag3Tl2Mo15S19, two novel members of the series M2Mo15X19 (M = In, Tl, K, Rb, Cs, Ba; X = S, Se). While only single crystals of Tl2Mo15S19 were obtained, Ag3Tl2Mo15S19 powders were synthesized, allowing for a study of its thermoelectric properties. Their structures contain Mo6S8iS6a and Mo9S11iS6a units separated by Tl+ cations. Silver insertion increases the electron transfer towards the Mo clusters leading to modifications of the Mo-Mo distances. Electrical resistivity measurements on Tl2Mo15S19 evidence its metallic character. Inserting Ag drives the transport properties towards a semiconducting state characterized by relatively low electrical resistivity and thermopower values. The large, complex unit cell of these compounds results in very low lattice thermal conductivity values below 1 Wm−1 K−1. Although the Ag insertion improves the thermoelectric performances, the ZT value remains moderate with a maximum value of 0.2 at 800 K.
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Gougeon et al. - 2020 - Synthesis, Crystal Structure and Transport Propert.pdf (1.48 Mo)
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