THERMOPOWER AND ELECTRICAL RESISTIVITY OF LaxY1−xAl2 ALLOYS

Abstract

The electronic transport theory predicts linear temperature dependences for the thermopower (S) and the electrical resistivity (ρ) at elevated temperatures. However, the experimental data for La x Y 1− x Al 2 alloys reveal nonlinear dependences for both, S(T) and ρ (T) . We relate this disagreement to the density of states (DOS) structure in the vicinity of the Fermi level. Based on the linearised Boltzmann transport equation, we obtain from the experimental temperature dependences of ρ and S an electron dependent function ϕ(ε), reflecting the energy dependence of DOS and that of scattering processes. In the scope of Mott's s-d model the 1/ϕ(ε) function is proportional to the DOS near the Fermi level. A comparison of the 1/ϕ(ε) function with available band structure calculations shows good agreement for YAl 2 and LaAl 2. In the case of alloys, the structure of DOS may cause a temperature dependence of the impurity contribution to the resistivity but has only a minor effect on S(T) at evelated temperatures.