Electrical conductivity of liquid metals

Metals, which are excellent conductors of electricity and heat, occupy a special place in the study of the states of matter. Indeed, if a metallic body had to be defined by a single property, the best would undoubtedly be its thermal coefficient of resistivity. Indeed, the metallic state is characterized by a low electrical resistance that increases with temperature, doubling significantly on melting.

The study, both experimental and theoretical, of the electronic transport properties of metals and alloys in the liquid state underwent a revival in the 1960s, thanks to the work of Ziman and his collaborators . These authors developed a theory of resistivity and thermoelectric power, based on a combination of the electronic theory of metals and classical fluid theory.

Nevertheless, for an elementary study of resistivity, we can use the classical free-electron theory developed by Drude at the turn of the century. In this theory, the reciprocal actions of ions with conduction electrons are neglected, and the latter are assumed to be entirely free to move within the sample. The main success of this theory was the justification of Wiedemann and Franz's relationship between electrical and thermal conductivities, which had been established experimentally some time earlier. However, even in the case of metals that most closely resemble the free-electron model, such as sodium, copper and silver, it is not correct to neglect the influence of the electrostatic attraction of ions on the distribution of electronic charges, which is why, despite its successes, Drude's theory encountered serious difficulties. The most important of these concerned the mass heat, which is much higher than it actually is, and the law of variation of resistivity with temperature in T ^1/2 , which in fact varies proportionally with temperature.

This article presents a selection of experimental results on the resistivity of molten metals. Nevertheless, space is reserved for a brief account of the theory of conduction in metals, and a description of the main techniques for measuring the resistivity of liquid metals.