Forced bond ionization-driven design of ultralow lattice thermal conductivity materials for flexible thermoelectrics.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41348874.
- Also identified by DOI 10.1126/sciadv.adz7487 and PMC identifier 12680034.
- Licence recorded as CC BY-NC.
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Abstract
The search for development strategies that yield low κ<sub>lat</sub> has become the focus of thermoelectrics and barrier coatings. Here, we propose a "forced bond ionization" strategy by integrating conflicting coordination environments (planar three coordination versus tetrahedral four coordination of Cu) to form pseudo-tetrahedral structures. This approach induces partial ionization of Cu─I bonds in Cu<sub>5</sub>TeS<sub>3</sub>I<sub>3</sub> (CTSI), yielding a record-low κ<sub>lat</sub> of 0.17 W/(m·K) for dense inorganic polycrystals. The pseudo-tetrahedral configuration triggers shear modes, markedly reducing the transverse speed of sound (ν<sub>T</sub> = 839 m/s) and amplifying anharmonicity (Grüneisen parameter γ = 2.76). Theoretical analysis reveals that coordination preference competition provides Cu atoms a metastable site, promoting the disordered behavior. The corresponding vibrations of I atoms and disordered Cu atoms dominate the phonon scattering while the material having remarkable flexibility and certain thermoelectric potential. This work establishes a bond ionization-driven design paradigm for ultralow κ<sub>lat</sub> materials, marking a leap toward potential flexible thermoelectric applications.