Electronic Band Structure and Transport Properties of the Cluster Compound Ag₃Tl₂Mo₁₅Se₁₉

Patrick Gougeon (1) , Philippe Gall (1) , Rabih Al Rahal Al Orabi (1) , Benoît Boucher (1) , Bruno Fontaine (1) , Regis Gautier (1) , Anne Dauscher (2) , Christophe Candolfi (2) , Bertrand Lenoir (2)

1 ISCR - Institut des Sciences Chimiques de Rennes
2 IJL - Institut Jean Lamour

Mo-based cluster compounds are a large class of materials with complex crystal structures that give rise to very low lattice thermal conductivity. Here, we report on the crystal structure and transport property measurements (5–800 K) of the novel Tl-filled compound Ag₃Tl₂Mo₁₅Se₁₉. This compound adopts a crystal structure described in the rhombohedral R3c space group [a = 9.9601(1) Å, c = 57.3025(8) Å, and Z = 6] built by the covalent arrangement of octahedral Mo₆ and bioctahedral Mo₉ clusters in a 1:1 ratio, with the Ag and Tl atoms filling the large cavities between them. Transport property measurements performed on polycrystalline samples indicate that this compound behaves as a heavily doped semiconductor with mixed electrical conduction. Electronic band structure calculations combined with a semiclassical approach using the Boltzmann transport equation are in good agreement with these measurements. This compound exhibits a lattice thermal conductivity as low as 0.4 W m^–1 K^–1 because of highly disordered Ag and Tl atoms. Because of the low thermopower values induced by the mixed electrical conduction, the dimensionless thermoelectric figure of merit ZT remains moderate with a peak value of 0.18 at 750 K.

Domaines: Chimie inorganique; Science des matériaux [cond-mat.mtrl-sci]

Patrick Gougeon, Philippe Gall, Rabih Al Rahal Al Orabi, Benoît Boucher, Bruno Fontaine, et al.. Electronic Band Structure and Transport Properties of the Cluster Compound Ag₃Tl₂Mo₁₅Se₁₉. Inorganic Chemistry, 2019, 58 (9), pp.5533-5542. ⟨10.1021/acs.inorgchem.8b03452⟩. ⟨hal-02120748⟩