Thermal transport and Thermoelectrics

Understanding origin, effects and implications of thermal transport is of great interest for applications like energy devices and thermal management of electronics. The main control parameter of thermal transport is thermal conductivity of material, originating from scattering of phonons with different sources. By first principles density functional theory and Boltzmann transport theory we provide an explanation about the origin of striking variation of κlatt and its anisotropy in group-IV (Zr and Hf) and group-VI (Mo and W) TMDs. The lower thermal conductivity of group IV TMDs is substantiated by 4 times larger Grüneisen parameter (γ) and twice as large anharmonic scattering rate (Wanhar) as compared to the group-VI TMDs. The Born effective charges, which are very different for two class of materials, are the driving factor of this phenomena, as it quantifies interlayer van der Waals (vdW) interaction strengths. We report for the first time an inverse correlation between the strength of vdW interaction and anisotropy in thermal conductivity of these TMDs.

Reference

  1. R. Juneja, T. Pandey, and A. K. Singh, High Thermoelectric Performance in n-doped Silicon-Based Chalcogenide Si2Te3 Chem. Mater. 29, 3723 (2017)
  2. G. Yumnam, T. Pandey, and A. K. Singh, High temperature Thermoelectric Properties of Zr and Hf Based Transition Metal Dichalcogenides: A First Principles Study, J. Chem. Phys. 143, 234704 (2015) 
  3. T. Pandey, and A. K. Singh, Simultaneous enhancement of electrical conductivity and thermopower in Bi2S3under hydrostatic pressure, J. Mater. Chem. C, 4, 1979 (2016)
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