Thermal conductivity electrons. In this case the mean velocity is the Fermi velocity which is temperature independent. The mean free path is determined by the impurities and the crystal imperfections which are temperature independent as well. So the only temperature-dependent quantity is the heat capacity "c", which, in this case, is proportional to "T". So with "k" a constant. For pure metals such as copper, silver, etc. "l" is large, so the thermal conductivity is high. At higher temperatures the mean free path is limited by the phonons, so the thermal conductivity tends to decrease with temperature. In alloys the density of
Thermal conductivity the impurities is very high, so "l" and, consequently "k", are small. Therefore, alloys, such as stainless steel, can be used for thermal insulation. Thermal conductivity Thermal conductivity (often denoted "k", "λ", or "κ") is the property of a material to conduct heat. It is evaluated primarily in terms of Fourier's Law for heat conduction. In general, thermal conductivity is a tensor property, expressing the anisotropy of the property. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity. Correspondingly, materials of high thermal conductivity are widely used in heat