Multiple point-defect formation in Pb(Au) alloys: Observation by solute resistivity measurements

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Abstract
Resistance measurements were made on Pb(Sn), Pb(Tl), Pb(Cd), Pb(Hg), Pb(Ag), and Pb(Au) alloys between -196 and +240°C. Of these only the Pb(Au) alloys show a temperature-dependent solute resistivity, changing sharply from about 3.5 to 4.5 μΩcm/at.% between 100 and 200°C, the transition temperature increasing with Au concentration. Comparison with data on Au diffusivity in Pb as a function of temperature and concentration shown that these data cannot be consistently described by a simple singletdoublet equilibrium. We therefore investigate singlet-doublet-triplet and singlet-doublet-quadruplet equilibria, concluding that the latter is slightly superior for describing the extant data. The enthalpy per atom of forming the multiplet appears to be 9-11 kcal/mole, compared to about 3.5 to 5.2 kcal/mole for forming the doublet. We also show that these multiplet models adequately describe the low-temperature precipitation behavior of Au in concentrated Pb(Au) alloys.