Heat Conduction in Complex Metallic Alloys

Thermal conductivity, κ, of ε-phase Al73Pd25Fe2 and "Bergman phase" Mg-Al-Zn is presented, which resembles the features common to all complex metallic alloys: relatively low value, shallow local maximum or change of slope at approximately 50 K, and a rise above 100 K. The electron contribution, κel, is calculated using Wiedemann-Franz law, while the calculation of the phonon thermal conductivity, κph, below 50 K is calculated employing Debye model. The sum of the two does not explain the experimental data at higher temperatures (above 100 K). This discrepancy is analyzed in three competitive ways: assuming an increase of an effective Lorenz number, taking into account the hopping of localized lattice vibrations, and employing a "bipolar diffusion effect", known from the theory of semiconductors. While the results of the former two approaches confirm other findings in literature, "bipolar diffusion effect" needs to be adopted for the specific electron structure of complex metallic alloys.