Tuning stability, mechanical, and electronic properties of orthorhombic Ag₃Sn via X doping (X = Au, Co, Cu, Ni, Sb, Zn): A first-principles investigation

Ag₃Sn, a critical intermetallic compound in Sn-Ag and Sn-Ag-Cu lead-free solders, suffers from limited ductility and high electrical resistivity, limiting joint reliability. To address these limitations, this paper investigated the doping of Au, Co, Cu, Ni, Sb, and Zn into Ag₃Sn via first-principles calculations, focusing on the stability, mechanical, and electronic behaviors. The results reveal that only Au and Ni dopants form thermodynamically stable phases. Mechanically, Au doping improves toughness while reducing the elastic modulus, whereas Ni doping enhances both toughness and elastic modulus. Both dopants increase elastic anisotropy, except for Ag_0.5Au_2.5Sn and Ni₃Sn. Electronically, Ni doping shifts the density of states (DOS) peak toward the Fermi level, with DOS values at the Fermi level rising significantly from 2.32 states/eV to 4.89 states/eV, suggesting an improvement in electrical conductivity. These findings suggest that Au and Ni are strategic dopants for optimizing Ag₃Sn's mechanical and electronic performance in advanced solder applications.