Interfacial wettability and electrical properties of Ni-doped Ag/Bi₂Sn₂O₇ electrical contact materials

Ag/Bi₂Sn₂O₇ materials have high electrical conductivity but mechanical properties similar to those of Ag/SnO₂ owing to their poor Ag/Bi₂Sn₂O₇ interfacial wettability. In this study, Ni-doped Ag/Bi₂Sn₂O₇ was prepared by high-energy ball milling, powder metallurgy, and extrusion. The microstructures and physical, mechanical, and electrical properties of Ag/Bi₂Sn₂O₇ (Ni-doped) materials with different Ni molar fractions were investigated by XRD, SEM, XPS, Hall-effect tests, metal resistivity measurements, tensile tests, and electrical life tests. The formation of a crystalline Ni-containing solid solution is also confirmed. With an increase in the Ni-doping molar fraction from 0 to 8.3%, the resistivity of the Ni-doped Bi₂Sn₂O₇ powder increased, the Ag/Bi₂Sn₂O₇ interfacial wetting angle decreased from 104.6°, to 83.1°, the hardness and density of the Ag/Bi₂Sn₂O₇ (Ni-doped) material first increased and then decreased, while the resistivity exhibited an opposite tendency. The Ag/Bi₂Sn₂O₇–5.2Ni (sheets) exhibited the lowest resistivity of 2.00 µΩ·cm, the highest hardness of 687 MPa, and the highest density of 9.99 g/cm³; its electrical life was 1.6 and 1.8 times that of Ag/Bi₂Sn₂O₇ and Ag/SnO₂, respectively. Thus, an appropriate amount of Ni-doping can improve the interfacial wettability, physical properties, and electrical properties of Ag/Bi₂Sn₂O₇ electrical contact materials.