Thermal Conductivity: Nonmetal Impact on Change

Click For Summary

Discussion Overview

The discussion revolves around the factors influencing thermal conductivity in nonmetals, particularly focusing on the role of lattice vibrations and temperature effects. Participants explore the relationship between temperature, phonon collisions, and heat transport mechanisms.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that thermal conductivity in nonmetals is determined by the propagation of lattice vibrations and questions how increasing temperature affects this conductivity.
  • Another participant speculates that phonon collisions may act as resistance, potentially leading to a decrease in conductivity with rising temperature.
  • A different viewpoint introduces the concept of ballistic transport at very low temperatures, where the absence of collisions allows for rapid heat transmission.
  • One participant mentions Umklapp scattering processes as a mechanism that can reduce heat transport, noting that this effect is significant at higher energies, which may or may not include room temperature depending on the material.

Areas of Agreement / Disagreement

Participants express differing views on the impact of temperature on thermal conductivity, with no consensus reached on whether conductivity increases or decreases with temperature in nonmetals.

Contextual Notes

The discussion includes assumptions about the behavior of phonons and the conditions under which different transport mechanisms dominate, such as the significance of Umklapp scattering at various energy levels.

aaaa202
Messages
1,144
Reaction score
2
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?
 
Physics news on Phys.org
What would you guess?
 
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?
 
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.
 
  • Like
Likes   Reactions: 1 person

Similar threads

  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
8K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 9 ·
Replies
9
Views
14K
Replies
1
Views
1K
  • · Replies 26 ·
Replies
26
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K