Thermal Conductivity of Germanium from 3°K to 1020°K

The thermal conductivity of germanium has been measured from 3^∘{}K to 1020^∘{}K. From 3^∘{}K to 300^∘{}K a longitudinal heat flow method was used. A radial flow method employing small samples was used from 300^∘{}K to 1020^∘{}K. The advantages and special experimental techniques required in this radial method are discussed. From 3^∘{}K to 10^∘{}K the results are explained by a simple combination of boundary plus isotope scattering in which all phonon-phonon processes can be neglected. At all temperatures below 940^∘{}K the heat is carried by phonons, but at 940^∘{}K a sharp rise in the thermal conductivity indicates the presence of a second conduction mechanism which may be electron-hole pairs.