CORRELATION OF SUBSOLIDUS PHASE-RELATIONS IN THE AG-PD-O SYSTEM TO OXIDATION REDUCTION KINETICS AND DILATOMETRIC BEHAVIOR

The relationship between the equilibrium subsolidus phase diagram of the Ag-Pd-O2 system, and the oxidation/reduction kinetics and microstructure development of 70Ag/30Pd coprecipitated and alloyed powders is presented. For the same Ag/Pd ratio and similar powder characteristics, the onset temperatures of Pd oxidation and PdO reduction for coprecipitated powders are lower than those of alloyed powders. For Ag/Pd alloyed powders, complete oxidation of Pd does not occur, because of kinetic limitations and the equilibrium phases present at high temperatures. Significant differences in microstructural evolution were observed and correlated to the oxidation processes and densification kinetics. The impact of these results on the use of the Ag/Pd system as conductors is discussed.