Calculation And Research On Doping Modification Of AgSnO₂ Contact Material

Electrical contact switches for breaking and isolating circuit affect the reliability and stability of the whole system.AgSnO₂ is widely used as electrical contact material,due to its advantages of non-toxic,environmental protection and excellent resistance to arc erosion.But the SnO₂ is a kind of wide band gap semiconductor material,which has high melting point and high hardness,resulting the increase of contact resistance and temperature.Therefore,the key to solve the problem is to improve the electrical performance of SnO₂.The study shows that doping third phase can effectively improve the electrical properties of SnO₂,also the AgSnO₂ materials.Firstly,pure SnO₂ and Fe?Bi?Cu?Mg?In doped SnO₂ were calculated by first-principle calculation.Through the geometry optimization and energy calculation,the band structure,density of states,charge density and differential charge density distribution were obtained,which showed that the electrical conductivity of SnO₂ electrical contact material were improved after doping.The doping elements with the best conductivity were Fe and Bi,followed by Cu,Mg and In.The five different elements doped SnO₂ were prepared by sol-gel method.Through the XRD test,the crystal structure of SnO₂ didn't change and the solid solution formed after the doped atoms entered into the SnO₂ cell.The powder size was calculated to be nano scale.Finally,the doping system model was established,and the diffraction pattern of the doped system was obtained by simulating X ray diffraction.It was theoretically verified that the crystal structure didn't change after doping.AgSnO₂ contact materials were processed into contact by the method of powder metallurgy.The electrical conductivity,density and hardness were measured,and electrical contact test was carried out to measure the contact resistance,welding force and arc energy.The results showed that the electrical conductivity,density and hardness of the doped AgSnO₂ contact material were improved.Considering the conductivity of the material and the welding resistance,the properties of Bi doped AgSnO₂ contact materials were optimized.