Phonon‐Dislocation Scattering and Low‐Temperature Lattice Thermal Conductivity of Niobium and Tantalum Single Crystals Deformed at Low Temperatures

The thermal conduction of niobium and tantalum single crystals plastically deformed in steps at low temperatures is measured between 0.3 and 20 K. The dislocation arrangement is studied by X‐ray topography and transmission electron microscopy. The thermal resistivity Wd due to the plastic deformation deduced in the temperature range 0.3 K < T < 5 K is found to be proportional to about T−3 after weak deformation. Strong deformation gives rise to a thermal resistivity proportional to T−2. The results are consistent with the model of scattering of phonons by the static distortion field of dislocations.