Formation of palladium oxides by mechanochemical reaction on Pd and Ag-Pd alloy contacts

The authors have already reported that when Pd contacts are operated in mechanical break-make actions without switching load current in air (laboratory atmosphere), palladium oxides are formed on the contact surfaces by a mechanochemical reaction and cause a marked increase of contact resistance. The formation of the same products on Ag-Pd 70% and Ag-Pd 50% contacts after tests involving 100000 operations are reported. Significant increase of contact resistance, however, was not observed. However, nonlinearity of contact resistance, as revealed by both dynamic and static current measurement, was observed. Temperature calculation shows that softening of the electrodes is not the main reason for the phenomenon. Other reasons, such as thermal dissolution of the contaminant layer, are suggested instead