Grain-size dependence and anisotropy of nanoscale thermal transport in MgO

DOI PDF 3 Citations 36 References Open Access
  • Susumu Fujii
    Division of Materials and Manufacturing Science, Osaka University 1 , Suita, Osaka 565-0871, Japan
  • Kohei Funai
    Department of Adaptive Machine Systems, Osaka University 3 , Suita, Osaka 565-0871, Japan
  • Tatsuya Yokoi
    Department of Materials Physics, Nagoya University 4 , Chikusa, Nagoya 464-8603, Japan
  • Masato Yoshiya
    Division of Materials and Manufacturing Science, Osaka University 1 , Suita, Osaka 565-0871, Japan

Abstract

<jats:p>Controlling thermal conductivity in nanocrystalline materials is of great interest in various fields such as thermoelectrics. However, its reduction mechanism has not been fully given due to the difficulty to assess local thermal conduction at grain boundaries (GBs) and grain interiors. Here, we calculated spatially decomposed thermal conductivities across and along MgO symmetric GBs using perturbed molecular dynamics, varying the GB separation from 2.1 to 20.0 nm. This reveals the different length scale of GB scattering for two directions: over hundreds of nanometers across GBs while within a few nanometers along GBs. Numerical analyses based on the spatially decomposed thermal conductivities demonstrate that the former is dominant upon suppressing thermal conductivity in polycrystalline materials, whereas the latter has a non-negligible impact in nanocrystalline materials because of a large reduction of intragrain thermal conductivity along GBs. These insights provide the exact mechanisms of heat transport in nanocrystalline materials toward more precise control of thermal conductivity.</jats:p>

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