Properties of AgSnO2 Contact Materials Doped with Different Concentrations of Cr.

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.

Study on Simulation and Experiment of Cu, C-Doped Ag/Ni Contact Materials.

Ag/Ni contact material with greenery and good performance is a cadmium-free silver-based contact material that has been vigorously developed in recent years. However, Ag/Ni contact material has poor welding resistance. Based on the first principles of density functional theory, the interface model of Cu, C-doped Ag/Ni was established. The work of separation and interfacial energy of interface models showed that doping can improve the interfacial bonding strength and interfacial stability, with C-doped Ag/Ni having the strongest stability and interfacial bonding strength. It can be seen from the population and density of state that covalent bonds exist between Ag and Ni atoms of the Ag/Ni phase interface at the electronic structure level. Finally, the doped Ag/Ni contact material was prepared by the powder metallurgy method. Through the arc energy and welding force in the electrical contact experiment, it was obtained that the welding resistance of C-doped Ag/Ni was better than Cu-doped Ag/Ni contact material, which verified the correctness of the simulation results. Overall, the present study provides a theoretical method for the screening of doping elements to improve the performance of Ag/Ni contact material.