Engineering Transport Properties in Interconnected Enargite‐Stannite Type Cu2+x Mn1−x GeS4 Nanocomposites

• Published in: Angewandte Chemie International Edition Vol. 61; no. 49
• Main Authors: Pavan Kumar, V., Passuti, S., Zhang, B., Fujii, S., Yoshizawa, K., Boullay, P., Le Tonquesse, S., Prestipino, C., Raveau, B., Lemoine, P., Paecklar, A., Barrier, N., Zhou, X., Yoshiya, M., Suekuni, K., Guilmeau, E.
• Format: Journal Article
• Language: English
• Published: Hoboken John Wiley and Sons Inc 05.12.2022
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202210600

Understanding the mechanisms that connect heat and electron transport with crystal structures and defect chemistry is fundamental to develop materials with thermoelectric properties. In this work, we synthesized a series of self‐doped compounds Cu 2+ x Mn 1− x GeS 4 through Cu for Mn substitution. Using a combination of powder X‐ray diffraction, high resolution transmission electron microscopy and precession‐assisted electron diffraction tomography, we evidence that the materials are composed of interconnected enargite‐ and stannite‐type structures, via the formation of nanodomains with a high density of coherent interfaces. By combining experiments with ab initio electron and phonon calculations, we discuss the structure–thermoelectric properties relationships and clarify the interesting crystal chemistry in this system. We demonstrate that excess Cu + substituted for Mn 2+ dopes holes into the top of the valence band, leading to a remarkable enhancement of the power factor and figure of merit ZT . A particular biphasic compound, which consists of interconnected enargite‐ and stannite‐type tetrahedral frameworks at the nanoscale, has been synthesized. The complex crystal chemistry of such nanocomposites raises the issue of the role of the two structures and of their interfaces in the mechanism governing their electrical and thermal conductivities.