An experimental investigation of the electrical and thermal conductivity of iron and some dilute iron alloys at temperatures above 100°K

Conductivity measurements have been performed at 90–300°K on iron of high purity and dilute alloys of this metal with Mn, Ni or Si. For the elimination of the parasitic thermal losses in the heat-conductivity measurements a special method has been worked out. The validity of the Wiedemann-Franz-Lorenz law (W-F-L law) for the investigated substances is examined. This analysis is extended to about 1300°K by use of conductivity values for iron and steels given in the literature. It is found that the part of the heat-resistivity of the electrons caused by lattice vibrations is fairly independent of temperature, in accordance with a previous statement by linde for non-transition metals. A modified form of the W-F-L law, written Ke(ρ + \̄gro) = LT, is put forward, and it is shown that this is generally valid for transition as well as non-transition metals at temperatures above the T5-region of ρ. The constant \̄gro of the suggested formula can be obtained from electrical measurements. If expressed as Kg = K-Ke, the lattice conductivity of iron shows an anomalous change at the Curie point, being much larger in the state of spontaneous magnetization than in the paramagnetic state. The spin-disorder part of the electrical resistivity is found to be proportional to T3 in the temperature range < 1000°K. Some abnormal behaviour of the residual resistivity of iron when measured on wires of varying diameters is discussed. The general results of the investigation concerning ρ, Ke and Kg are given in the form of graphs of conductivity and resistivity-quantities as functions of temperature.