Effect of Dislocations on Low-Temperature Thermal Conductivity and Specific Heat of Copper-Aluminum Alloy Crystals

Abstract

Simultaneous measurements of the thermal conductivity and specific heat of copper-aluminum (2, 5, 8, and 12 at.%) alloy crystals have been done by the temperature-wave method at 1.4–7.5 K. Specimens containing dislocations of medium (10¹⁰ cm⁻²) and high (10¹² cm⁻²) densities were used. In the case of crystals of medium dislocation density, the lattice thermal conductivity data were well explained by the mechanism of the strain-field scattering of phonons, and the numerical results agreed with those recently calculated by the authors. The lattice specific heat of the crystals was found to be strongly decreased by the introduction of dislocations, and the results were interpreted by considering the effect of atmosphere of alloying atoms. Anomalous behaviors of the specific heat and thermal conductivity were found in crystals of high dislocation density. The origin was assumed to be quasi-local phonon modes around dislocations, and the analysis of the data along this idea gave reasonable results.