Preparation And Conductive Properties Of Ag/Cu/Sn Alloy Nanopowders

With the development of electronic products towards the trend of intelligence,miniaturization,flexibility and network interconnection,it is urgent to develop matched powder materials.Silver powder with excellent electrical conductivity and thermal stability has widely been used in electronic packing and printing electronics.However,the self-transfer for Ag is likely to cause sharp increases of resistance or short circuit phenomenon when devices work.Cu and Sn metals are low-price,but have poor thermal stability,which limits large-scale applications as a substitute of silver metal.It would be an economical and effective way that Ag alloyed powders containing an amount of Cu or Sn consents take over pure Ag powders.On the other hand,the DC arc plasma method has hosts of advantages in terms of nanopower preparation,including high purity,simple production process,high yield and environmentally friendly practice.In this paper,Ag-Cu,Sn-Ag and Sn-Ag@C alloy nanopowders were prepared under different conditions using DC arc plasma method.The structure and morphology of nanopowders were characterized by XRD,TEM,XPS and EDS.The thin slice resistivity of the samples was measured by four-probe method for electrical properties estimation,and the thermal stability of the nanopowders was investigated by TGA.Through the analysis and discussion of the experimental results,the conclusions are as follows:?1?The structure and morphology of alloy nanoparticles.Ag-Cu alloy nanoparticles present spherical with an oxide layer and a particle size of 80-90 nm.Ag and Cu exist in the form of mutual solid solution.Sn-Ag alloy nanoparticles,spherical and larger than 100 nm,are mainly composed of Ag₃Sn and elemental Sn phases.Compared with Sn,the oxide layer on the surface of Ag₃Sn is thinner.Surface oxide of alloy particle mainly consists of SnO_x.Sn-Ag@C nanocomposite particle presents an one-dimensional rod-like structure with a length of 100-200nm,and a spherical end which has a diameter of 20-30 nm.The surface is coated by carbon layer those thickness is 2-3 nm,under which there is a small amount of SnO_x oxide.The catalytic effect of Sn is the main cause of the formation of rod-shaped particles.?2?The electrical conductivity and thermal stability of alloy nanoparticles.Compared with Cu and Sn metallic nanopowders,the conductivity of alloy nanopowders is higher,and the higher the content of Ag,the better the conductivity.The conductivity of Sn-Ag alloy nanopowders is superior than that of Ag-Cu alloy nanopowders with the same silver contents.Sn-Ag@C nanoparticles exhibit a dielectric behavior,and their conductivity mechanism can be explained by the electron-limiting theory.High-temperature sintering results in the decomposition of silver oxide into elemental silver,which significantly reduces the resistivity of Ag-Cu alloy nanopowders,but has little effect on that of Sn-Ag and Sn-Ag@C nanopowders.Thanks to the thin oxide layer produced during the passivation,the oxidation resistance of the alloy nanoparticles can be improved.Whilst Sn-Ag@C nanoparticles have the best antioxidant ability,indicating that the carbon layer is capable of isolating oxygen,the antioxidant ability decreases after the temperature is higher than 365?due to the ablation of the carbon layer.