Unravelling the influence of the local structure on the ultralow thermal conductivity of the bismuthinite-aikinite series, Cu1–x□xPb1–xBi1+xS3

Vaqueiro, P. ORCID: https://orcid.org/0000-0001-7545-6262, Herlihy, A., Elgaml, M., Mukherjee, S., Keen, D. A., Voneshen, D. J. and Powell, A. V. (2025) Unravelling the influence of the local structure on the ultralow thermal conductivity of the bismuthinite-aikinite series, Cu1–x□xPb1–xBi1+xS3. Journal of the American Chemical Society, 147 (41). pp. 37598-37610. ISSN 1520-5126 doi: 10.1021/jacs.5c12526

Abstract/Summary

Understanding the relationship between crystal structure, bonding and thermal transport is critical for the discovery of materials with ultralow thermal conductivities. Materials in the bismuthinite-aikinite series, Cu1–x□xPb1–xBi1+xS3 (0 <= x <= 1), in which a Bi3+ cation and a vacancy (□) are progressively substituted by a Pb2+ and a Cu+ cation, exhibit ultralow thermal conductivities (~ 0.5 Wm-1K-1 for x < 1). Here, we investigate the effect of decreasing the Pb2+ and Cu+ content on the crystal structure and properties of Cu1–x□xPb1–xBi1+xS3 (x = 0, 0.33, 0.6 and 0.83). These materials exhibit two-channel thermal transport, with non-propagating phonons being the dominant contribution. Neutron diffraction data reveal that intermediate compositions crystallise in the krupkaite structure (x = 0.5, P21ma), instead of the end-member aikinite structure (x = 0, Pnma). Pair distribution function (PDF) analysis reveals that the disordering of vacancies and cations deviates significantly from that expected for a statistical distribution and that, at a local level, copper-rich and copper-poor regions occur. Reducing the Pb²⁺ and Cu⁺ content results in lattice softening, which may be attributed to the increased concentration of vacancies in copper-poor regions. Moreover, the persistence of short Pb2+-Cu+ distances in the copper-rich regions is likely to facilitate the cooperative interaction between lone pairs and rattling Cu+ cations that leads to phonon scattering. These findings provide crucial insights into the effect of the local structure on the phonon transport and highlight the potential of local-structure design to achieve high thermoelectric performance in crystalline solids.

Item Type	Article
URI	https://centaur.reading.ac.uk/id/eprint/124334
Identification Number/DOI	10.1021/jacs.5c12526
Refereed	Yes
Divisions	Interdisciplinary centres and themes > Chemical Analysis Facility (CAF) Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry Interdisciplinary centres and themes > Energy Research
Publisher	American Chemical Society
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