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As an important component carrying the core function and service life of switching appliances, the selection and improvement of electrical contact materials is of great significance. AgSnO2, which is non-toxic, environmentally friendly and has excellent performance, has become the most promising contact material to replace AgCdO. However, it has deficiencies in machinability and electrical conductivity. The property of AgSnO2 contact material was improved by doping element Cr. The relationship between the mechanical and electrical properties of AgSnO2 contact materials and doping concentrations were investigated and analyzed by simulation and experiment. Based on the first principle, the elastic constants of supercell models Sn1−xCrxO2 (x = 0, 0.083, 0.125, 0.167, 0.25) were calculated. The results show that the material with a doping ratio of 25% is least prone to warp and crack, and the material with a doping ratio of 12.5% has the best toughness and ductility and the lowest hardness, which leads to molding and is subsequently easier to process. The Cr-doped AgSnO2 contacts with different doping proportions were prepared by the sol–gel and powder metallurgy method. Additionally, their physical performance and electrical contact properties were measured in experiments. The results show that the doped SnO2 powders prepared by the sol–gel method realize integration doping, which is consistent with the crystal model constructed in the simulation calculation. Sn0.875Cr0.125O2 has lower hardness, which is beneficial to process and form. Doping helps to stabilize the arc root, inhibit the ablation of contact by arc, reduces arc duration and arc energy, improves the resistance to arc erosion of AgSnO2 contact material, and makes electrical contact performance more stable. The contact material with a doping concentration of 16.7% has the best arc erosion resistance. [ABSTRACT FROM AUTHOR]

AgSnO2, as the most potential material to replace AgCdO, is widely used in low-voltage electrical appliances. However, because of the high hardness and poor conductivity of SnO2, AgSnO2 has the problems of processing difficulties and large contact resistance. Based on the first principles of density functional theory, a method is proposed to calculate the electronic structure and mechanical properties of SnO2, SnO22Ce, SnO2–N, and SnO22–Ce–N. By analyzing the energy band, density of states, and elastic constants, the results show that Ce–N co-doped SnO2 has the highest relative conductivity, reduced hardness, and increased ductility and overcome processing difficulty. The doped AgSnO2 contact material was prepared by sol–gel method and powder metallurgy method, and the hardness and electrical properties of the sample were tested. The experimental results show that AgSnO2–Ce–N contacts have higher conductivity, lower contact resistance and arc energy, and lower hardness. The theory is consistent with the experiment, proving the feasibility of simulation. Therefore, Ce and N co-doping can effectively overcome the disadvantages of AgSnO2 contact materials, improve conductivity, and overcome processing difficulty. It provides a new idea and theoretical basis for the doping research of AgSnO2 contact materials. [ABSTRACT FROM AUTHOR]

The first-principles method based on density functional theory was used to analyze the impurity formation energies, energy bands, density of states, electron overlap population and elastic modulus of SnO2, SnO2–Ni, SnO2–N and SnO2–Ni–N. SnO2 powders with different additives were prepared by the sol-gel method, and then X-ray diffraction experiments and wettability experiments were carried out. The powder metallurgy method was used to prepare AgSnO2 contacts with different additives. The simulation experiments on hardness, electrical conductivity and electrical contact were carried out. The simulation results show that the conductivity of Ni–N co-doped SnO2 is best, and more impurity levels are introduced into the forbidden band, thereby increasing the carrier concentration, reducing the band gap, and improving the conductivity. The experimental results show that Ni, N doping does not change the structure of SnO2, so doped SnO2 still belongs to the tetragonal system. Ni–N co-doping can better improve the wettability between SnO2 and Ag, reduce the accumulation of SnO2 on the contact surface and reduce the contact resistance. Ni–N co-doped SnO2 has the smallest hardness, improving ductility, molding and service life of the AgSnO2 contact material. [ABSTRACT FROM AUTHOR]