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 containing "I" terms have to be zero. Now if we assume that where "δ" is the Dirac delta function, "I" terms get the following expressions By substituting these expressions to the equation for "λ", we see that it goes to zero. Therefore, "P"("x") has to be delta function. In an isotropic medium the thermal conductivity is the parameter "k" in the Fourier expression for the heat flux where formula_2 is the heat flux (amount of heat flowing per second and per unit area) and formula_66 the temperature gradient. The sign in the expression is chosen so that always "k" >