Thin-film reactions of Pb with AgAu and AgPd alloys

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Abstract
Stability of AgAu and AgPd alloys with respect to their reactions with Pb have been studied by using thin‐film samples and by free‐energy calculations. Thin‐film reactions of Pb with 80 at.% Ag‐20 at.% Au and 80 at.% Ag‐20 at.% Pd alloys were examined by x‐ray diffraction. X‐ray results show that the AgAu alloy is stable with Pb up to 200 °C and the AgPd alloy is stable with Pb at room temperature but unstable at 200 and 250 °C resulting in the formation of Pb2Pd along with a dilute phase of Ag which is almost free of Pd. Free‐energy calculations show that Pb cannot deplete Au from any AgAu alloy which contains less than 29.5 at.% Au, and yet Pb can deplete Pd down below 1 at.% from any AgPd alloys provided that the kinetics is fast enough.