Temperature dependence of thermal conductivity for MgxSi 1-xGex solid solution

The thermal conductivity of n-type Mg₂Si_0.6Ge_0.4 doped with 8000 ppm of Sb was measured over the temperature range from 80 to 350 K. The measurement was carried out by a comparative static method using transparent quartz as a reference specimen. The carrier concentration at 300 K was 6.25×10²⁵ m^-3 determined from Hall measurement. The Hall coefficient was almost constant over the whole temperature range, which indicates the degenerate state of electrons. The κ was separated into two components of phonon κ_ph and electron κ_el on the basis of Wiedemann-Franz law. Assuming that the Lorenz number is 2.44×10^-8 V²/K² which is a value for a metal and using values of the electrical conductivity σ, it was found that κ _ph has a temperature dependence proportional to T^-1/2 and that point defects related to the mass difference between Si and Ge is predominant for the phonon conduction