<Dl> <Dd> k = k 0 T (metal at low temperature) (\ displaystyle k = k_ (0) \, T (\ text ((metal at low temperature)))) </Dd> </Dl> <Dd> k = k 0 T (metal at low temperature) (\ displaystyle k = k_ (0) \, T (\ text ((metal at low temperature)))) </Dd> <P> 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 the impurities is very high, so l and, consequently k, are small . Therefore, alloys, such as stainless steel, can be used for thermal insulation . </P>

Thermal conductivity as a function of temperature equation