Effect of In₂O₃ Additive Size on the Mechanical Behavior of Densified Ag-SnO₂ Contact Materials

The nano and sub-micron In₂O₃ powders were respectively used as additive to improve the mechanical properties of the densified Ag-SnO₂ contact materials. The compressive fracture mechanism was analyzed by microstructure characterization and numerical simulations. It was found that the size of the In₂O₃ powders had obvious effect on the mechanical behavior of the Ag-SnO₂ materials. The materials with nano In₂O₃ additive exhibited the excellent physical and mechanical properties. The optimal mass fraction of the nano In₂O₃ additive in the materials was 1.0%. The electrical conductivity and relative density were increased to 77.0%IACS and 99.6%, respectively. Under the compressive loading, the initiation of the internal cracks led to the fracture of the Ag-SnO₂ contact material without additive. Notably, the nano In₂O₃ additive effectively relieved the stress and strain concentrations inside the Ag-SnO₂ material, and the crack initiation was effectively suppressed, which was beneficial for improving compressive strength. However, it should be noted that the sub-micron In₂O₃ additive about 400 nm inevitably induced the severe local strain and generated the cracks in Ag-SnO₂ material, resulting in the decrease of compressive strength. In addition, the layered microstructure was formed along the longitudinal section of the compressed Ag-SnO₂ material with nano In₂O₃ additives due to the larger plastic deformation.