Lone-Electron-Pair Micelles Strengthen Bond Anharmonicity in MnPb16Sb14S38 Complex Sulfosalt Leading to Ultra-Low Thermal Conductivity

• Published in: ACS applied materials & interfaces Vol. 12; no. 40
• Main Authors: Dawahre, Lamia, Lu, Ruiming, Djieutedjeu, Honore, Lopez, Juan S., Bailey, Trevor P., Buchanan, Brandon, Yin, Zhixiong, Uher, Ctirad, Poudeu, Pierre F. P.
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society (ACS) 09.09.2020
• Subjects: Bond anharmonicity; Hierarchical structure; Lone electron pair micelles; MATERIALS SCIENCE; Paramagnetism; Sulfosalt; Ultra-low thermal conductivity
• ISSN: 1944-8244; 1944-8252

Designing crystalline solids in which intrinsic extremely low lattice thermal conductivity mainly arises from its unique bonding nature rather than structure complexity and/or atomic disorder could promote thermal energy manipulation and utilization for applications ranging from thermoelectric energy conversion to thermal barrier coatings. Here, we report an extremely low lattice thermal conductivity of ~0.34 W m-1 K-1 at 300 K in the new complex sulfosalt MnPb16Sb14S38. We attribute the ultra-low lattice thermal conductivity to a synergistic combination of scattering mechanisms involving (1) strong bond anharmonicity in various structural building units, owing to the presence of stereoactive lone-electron-pair (LEP) micelles, and (2) phonon scattering at the interfaces between building units of increasing size and complexity. Remarkably, low-temperature heat capacity measurement revealed a Cp value of 0.206 J g-1 K-1 at T > 300 K, which is 22% lower than the Dulong-Petit value (0.274 J g-1 K-1). Further analysis of the Cp data and sound velocity (ν = 1834 m/s) measurement yielded Debye temperature values of 161 K and 187 K, respectively. Here, the resulting Grüneisen parameter, γ = 1.65, further supports strong bond anharmonicity as the dominant mechanism responsible for the observed extremely low lattice thermal conductivity.