Crossover from Germanite to Renierite-Type Structures in Cu 22– x Zn x Fe 8 Ge 4 S 32 Thermoelectric Sulfides

Ventrapati Pavan Kumar (1) , Laura Paradis-Fortin (1, 2) , Pierric Lemoine (2) , Gérard Le Caër (3) , Bernard Malaman (4) , Philippe Boullay (1) , Bernard Raveau (1) , Gabin Guelou (1) , Emmanuel Guilmeau (1)

1 CRISMAT - Laboratoire de cristallographie et sciences des matériaux
2 ISCR - Institut des Sciences Chimiques de Rennes
3 IPR - Institut de Physique de Rennes
4 IJL - Institut Jean Lamour

Copper-rich sulfides with the composition Cu 22-x Zn x Fe 8 Ge 4 S 32 (0 ≤ x ≤ 2) have been investigated. The detailed structural study combining powder X-ray diffraction, electron microscopy and Mössbauer spectroscopy shows a crossover from a germanite-type domain for 0 ≤ x ≤ 0.4 to a renierite-type domain for 1.2 ≤ x ≤ 2.0, with a biphasic region for x = 0.8. Both sulfides are p-type thermoelectrics due to the presence of the conductive "Cu-S" network containing univalent copper as a major cationic element. All these sulfides exhibit a semiconducting behavior. However, the renierite-type sulfides show a higher resistivity and a lower thermal conductivity than the germanite ones. As a consequence, the ZT figures of merit are similar for germanite and renierite domains reaching values of around 0.23 at 700 K.

Mots clés: Germanite; Renierite; Disorder; Sulfide; Thermoelectric; Crystal structure; Chemical structure; Physical and chemical processes; Cations

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

Ventrapati Pavan Kumar, Laura Paradis-Fortin, Pierric Lemoine, Gérard Le Caër, Bernard Malaman, et al.. Crossover from Germanite to Renierite-Type Structures in Cu 22– x Zn x Fe 8 Ge 4 S 32 Thermoelectric Sulfides. ACS Applied Energy Materials, 2019, 2 (10), pp.7679-7689. ⟨10.1021/acsaem.9b01681⟩. ⟨hal-02354451⟩