Abstract: For the deficiencies of AgSnO₂ contact material, the first-principle based on the density functional theory was used to study the electrical and mechanical properties of pure SnO₂, Ni doped SnO₂, Mo doped SnO₂ and Ni-Mo co-doped SnO₂. The parameters of every model, including the formation energy, energy band structure, density of state, elastic constant were obtained by the CASTEP module of Materials Studio software. According to the formation energy, the doped models can exist stably. After doped, every model′s valence band top and conduction band bottom are at the same point so the doped models are still the direct bandgap semiconductor materials. The Ni-doped SnO₂ is P-type doped semiconductor material, and the Mo-doped is the N-type as well as Ni-Mo co-doped SnO₂. With the introduction of the new impurity levels, the band gap is narrowed. Compared with the band structure of pure SnO₂, the doped models have a rising valence band and a declining conduction band so they have a smaller band gap, and the Ni-Mo co-doped SnO₂ has the smallest band gap. With the reduced energy for carrier transition, the electrical performance of SnO₂ is improved largely. What′s more, the shear modulus, volume modulus and hardness are obtained by the elastic constants. The hardness of Ni-Mo co-doped SnO₂ decreases significantly and its toughness is enhanced, which is conductive to the subsequent processing and forming of AgSnO₂ contact material. The Ni-Mo co-doped SnO₂ has the smallest universal elastic anisotropy index so the contact materials are not easy to form cracks. According to the calculation results, it turns out that the co-doping of Ni-Mo can improve the electrical and mechanical properties of SnO₂ better than single element doping, which provides theoretical guidance for the further development and research of contact materials.

Key words: first-principle, SnO₂, Ni-Mo co-doped, stability, electrical property, mechanical property