Thermal transport crossover from crystalline to partial-crystalline partial-liquid state

• Published in: Nature communications Vol. 9; no. 1; pp. 4712 - 8
• Main Authors: Zhou, Yanguang, Xiong, Shiyun, Zhang, Xiaoliang, Volz, Sebastian, Hu, Ming
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 09.11.2018; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/119/2795; 639/638/563/606; Condensed Matter; Converters; Crossovers; Crystal structure; Crystallinity; Engineering Sciences; Fluidization; Fluidizing; Heat conductivity; Heat transfer; High temperature; Humanities and Social Sciences; Low temperature; Materials Science; Mean free path; Mechanics; Micro and nanotechnologies; Microelectronics; multidisciplinary; Phase change materials; Phonons; Physics; Science; Science (multidisciplinary); Temperature dependence; Thermal conductivity; Thermics; Transport; Vibrations
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-07027-x

Phase-change materials (crystalline at low temperatures and partial-crystalline partial-liquid state at high temperatures) are widely used as thermoelectric converters and battery electrodes. Here, we report the underlying mechanisms driving the thermal transport of the liquid component, and the thermal conductivity contributions from phonons, vibrations with extremely short mean free path, liquid and lattice-liquid interactions in phase-changed Li 2 S. In the crystalline state ( T  ≤ 1000 K), the temperature dependent thermal conductivity manifests two different behaviors, i.e., a typical trend of 1/ T below 800 K and an even faster decrease between 800 and 1000 K. For the partial-crystalline partial-liquid Li 2 S when T  ≥ 1100 K, the contributions of liquid and lattice-liquid interactions increase significantly due to the fluidization of Li ions, and the vibrations with extremely short mean free path, presumably assimilated to diffusons, can contribute up to 46% of the total thermal conductivity at T  = 1300 K. Phase-change materials are applied as thermoelectric converters and battery electrodes, but underlying mechanisms are not fully understood. Here, the authors comprehensively describe thermal transport mechanisms of lithium sulfide based on molecular dynamics and first-principles simulations.