Thermal conductivity

  1. For a nonmetal what determines thermal conductivity is the propagation of lattice vibrations. As T increases these lattice vibrations collide with each other more often. Does this mean that the thermal conductivity will de- or increase?
  2. jcsd
  3. DrDu

    DrDu 4,639
    Science Advisor

    What would you guess?
  4. Im guessing the phonon collisions act as a sort of resistance, so the conductivity drops with increasing temperature. But on the other hand, what if there were no collisions? What would then transmit heat?
  5. DrDu

    DrDu 4,639
    Science Advisor

    If there are no collisions, e.g. at very low temperatures, you have ballistic transport which is very rapid.
    I think that only so-called Umklapp scattering processes actually can reduce the heat transport and this requires the sum of the crystal momenta of the two phonons to be larger than a reciprocal lattice vector. So it is only important at relatively high energies ~ Debye energy. Whether this includes room temperature depends on the material.
    1 person likes this.
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