Calculation And Research On Electrical Properties Of Double Rare Earth Element Co-doped AgSnO₂ Contact Material

The electrical contacts of the switching appliance assume the task of connecting and cutting off the circuit,and its reliability affects the stability of the circuit.The new Ag Sn O₂material is an environmentally friendly material,and it is currently the most suitable electrical contact material to replace Ag Cd O.Ag Sn O₂has excellent comprehensive properties.But Ag Sn O₂also has some disadvantages,such as that Sn O₂crystals will be precipitated on the surface during the use of electric contact materials.However,Sn O₂is a kind of wide bandgap semiconductor,and Sn O₂has poor electrical conductivity,high melting point and high hardness,which results the contact resistance of the contact material increasing,temperature rising,and it will be difficult to process or mold the contact material.Those problems affects the use of electrical contacts.Therefore,how to improve the electrical conductivity of Sn O₂has become the main research direction of today’s scholars.Many studies have shown that doping other elements in Sn O₂can effectively improve the electrical properties of Sn O₂.When there are two or more types of elements doped with Sn O₂,the effect is often better.In this paper,the first-principles method based on density functional theory is used to simulate the construction of two sets of rare earth elements（Ce and Nd,La and Y）.And these four elements are mono-doped and co-doped in Sn O₂supercells.The doping ratio is set to 16.6%.Then their band diagrams,the densities of states,the charge distribution and the electrical conductivities were analyzed.The results show that both the single-doping and co-doping of rare earth elements can reduce the band gap of Sn O₂,and the energy band tends to be tighter,while the effects of Ce-Nd co-doping and La-Y co-doping Sn O₂are significantly better than each rare earth element is single-doped.The calculation results of electrical conductivity also show that the electrical properties of the Sn O₂system co-doped with Ce-Nd and La-Y are better than the Sn O₂system single-doped with rare earth elements.Among them,the La-Y co-doped Sn O₂crystal’s calculation results perform best.Then,the sol-gel method was used to prepare the intrinsic Sn O₂powder and the single-doped and co-doped Sn O₂powders of each group of rare earth elements.Finally,the prepared rare earth element doped gel Sn O₂powder was combined with Ag powder by powder metallurgy method.Through a series of processing,the intrinsic,single-doped and co-doped Ag Sn O₂electrical contact materials are obtained.Then those Ag Sn O₂electrical contact materials’physical properties（electrical conductivity,density,and hardness）and their electrical properties（contact resistance,arcing energy,material transfer）are measured.The test results are used to analyze the pros and cons of the material properties of the contacts,and then those results are compared with the results of simulation calculation results.The conclusion is that the conductivity,density,and hardness of the Ag Sn O₂contact material co-doped with La-Y and Ce-Nd are better than those of the rare earth element single-doped.The test results of contact resistance,arc resistance and material transfer amount show that the electrical properties of Ce,Nd,La,and Y rare earth element single-doped Ag Sn O₂contacts are better than intrinsic Ag Sn O₂contacts.The electrical properties of the Ce-Nd co-doped and La-Y co-doped Ag Sn O₂contact materials are superior to the individual rare earth element single-doped Ag Sn O₂contacts.And the experimental measurement results are consistent with the simulation calculation results,which proves the consistency between theory and practice.And the feasibility and correctness of the theoretical calculation method are verified.By comprehensively considering the physical and electrical properties of the material,it is concluded that the properties of the Ag Sn O₂contact material co-doped with La and Y elements are optimal.