Thermal conductivity the list of thermal conductivities. These should be considered approximate due to the uncertainties related to material definitions. High energy generation rates within electronics or turbines require the use of materials with high thermal conductivity such as copper "(see: Copper in heat exchangers)", aluminium, and silver. On the other hand, materials with low thermal conductance, such as polystyrene foam and fire brick, are used in building construction or in furnaces in an effort to slow the flow of heat, i.e. for insulation purposes. The reciprocal of thermal conductivity is "thermal resistivity", usually expressed in kelvin-meters per watt (K⋅m⋅W). For a
Thermal conductivity is the electronic thermal conductivity when the electrochemical potential gradient inside the sample is zero, as a starting point. As next step the transport coefficients are written as following where formula_56 and "a" the Bohr radius. The dimensionless integrals "I" are defined as where "s"("x") is the dimensionless transport distribution function. The integrals "I" are the moments of the function where "x" is the energy of carriers. By substituting the previous formulas for the transport coefficient to the equation for "λ" we get the following equation From the previous equation we see that "λ" to be zero the bracketed term