Resistivity of Liquid Lead-Tin Alloys

Abstract

The electrical resistivity of liquid lead-tin alloys has been measured as a function of temperature and composition up to 530°C by a dc potentiometric method. No anomalies were observed in the isotherms of resistivity or in the isotherms of the temperature coefficient of resistivity as a function of composition. This is in contrast to data obtained by a magnetic-induction eddy-current technique. The reported anomalies are thought to be a characteristic of the measuring technique, and may result in part from viscosity changes in the vicinity of the eutectic composition. The calculated resistivities of pure tin and lead are within about 20% of the experimental values. The experimental resistivity-composition isotherms deviate below the weighted mean values of the resistivities of the two components. The deviation is a maximum at the 50% alloy composition and varies from 2.5% at 300°C to 4% at 500°C. The shape of the isotherm is discussed in terms of the pseudopotential theory developed by Faber and Ziman. Evaluation of the substitutional-alloy formula, using the Heine and Abarenkov pseudopotential formulation and a structure factor independent of concentration, predicts that the isotherm at about 300°C should deviate by a maximum of about 2% below the weighted mean value. This is in excellent agreement with the experimentally observed resistivity deviation.