Preferential oxidation of intermetallic compounds in Ag-2Sn-4La alloy

The influence of trace La on the oxidation of Ag-Sn alloy has been widely discussed. Here we present a detailed study for evaluating the potential impact of high content La for the oxidation of Ag-Sn alloy. We found that there are two kinds of intermetallic compounds in Ag-2Sn-4La alloy. The intermetallic compounds underwent a preferential oxidation, and the corresponded precipitation sequence of oxides was La2O3, La2Sn2O7 and SnO2. Based on the acquired insight, we suggest that high content La can accelerate the oxidation of Ag-Sn alloy oxidation but is not beneficial for the microstructure design of Ag-SnO2 electrical contact material.