Metal–non-metal transition in lead–bismuth eutectic

Abstract

Abstract Thermodynamic functions and electrical resistivity of Pb–Bi eutectic alloy have been measured over wide ranges of specific volume and pressure in the liquid and gaseous state. The experimental data show a crossover from metallic to insulating behavior in the electrical resistivity of the alloy when its specific volume increases. It is found that in the crossover region the constant volume temperature coefficient of resistivity changes sign from positive to negative and passes through zero at a value of the specific volume which is 2.4 times larger than that in normal state. The second salient feature of the alloy revealed by these experiments is that the isochores plotted in the specific internal energy—pressure plane are straight lines. Based on these experimental data and using an earlier developed approach, an equation of state (EOS) of the alloy has been constructed whose accuracy is determined mainly by the errors of the measurements. It is shown that this EOS can be used to obtain direct estimates of the specific volume and pressure at the critical point of the liquid–gas transition as well as the critical volume for the metal–non-metal (M–NM) transition observed in this eutectic. The results indicate that the critical specific volumes for these two transitions are equal, and the M–NM transition can be described by the classical percolation theory.