Self-diffusion of lead, thallium and bismuth in the solid lead-thallium system

Abstract

Results are reported for the self-diffusion of both lead and thallium over the whole range of solid solution for these elements (0–87 atomic per cent T1) for the temperature interval, 206−323°C. Data for the trace impurity diffusion of bismuth over the same concentration range are also given for a more limited temperature range. All three elements show the same qualitative dependence of their diffusion coefficient upon alloy composition: namely, a slight maximum at about 35 atomic per cent thallium and a deep minimum at about 75 atomic per cent thallium at all temperatures. The results are compared with the predictions of the corresponding states principle and with theories based upon the Johnson vacancy-solute complex mechanism. A correction applied to the corresponding tates principle, based upon lattice parameter deviations fromVegard's Law, leads to agreement with observation. Some evidence for the existence of a superlattice at alloy compositions in the neighborhood of PbTl 7 is inferred from trends in the ratios D Tl / D Pb and D Bi / D Pb with thallium concentration.