The effect of impurities on the residual electrical resistivity of thallium
Аннотация
The effects of twelve impurities (Te, Sb, Bi, As, Ag, Mg, Cd, Sn, Pb, Hg, In, and Zn) on the residual resistivity (ρ0) of thallium have been studied. The thallium used was ≥ 99.999% pure with a resistance ratio δ0 = ρ0/ρ293 = 3.5 × 10–5, and the alloys were prepared in the concentration range from 1 × 10–3 to 2 wt.% with subsequent homogenization by annealing in a pure helium atmosphere. The values found for the change in residual resistance of thallium (Δρ0/c) upon dissolution of 1 at .% of impurity depend quadratically on the valence difference between impurity and host (Δ z) for the group V and VI impurities. Calculations of Δρ0/c have been carried out using phase shifts, using the form factors of Appapillai found from first principles, and using the Ashcroft model pseudopotential which showed that the latter case gives the best agreement with experiment (discrepancy no more than a factor of 2) with ∼0.5 conduction electrons per atom.