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

Ag 3 Sn, 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 Ag 3 Sn 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 0.5 Au 2.5 Sn and Ni 3 Sn. 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 Ag 3 Sn's mechanical and electronic performance in advanced solder applications. • Stable doping configurations are identified across elements/concentrations. • Au/Ni doping enhances Ag 3 Sn's stability. • Ni enhances both toughness and elastic modulus. • Ni elevates Fermi-level DOS, improving conductivity.