Phase evolution of binary immiscible Al-Sn film

Binary immiscible Al-Sn alloy is a very important potential anode material for lithium ion batteries.The phase stability and separation process of Al-Sn film,fabricated by magnetron co-sputtering method,was investigated by X-ray diffractometer(XRD),differential scanning calorimetry(DSC) and in situ transmission electron microscopy(TEM) and explained by Miedema theoretical model.Thermodynamic analysis reveals that the asdeposited Al-Sn film will decompose spontaneously into Al-riched areas and Sn-riched areas because of the positive mixing enthalpy.The crystallization process takes place when the Al content in the Al-riched area or Sn content in the Sn-riched area increases.Experimental results show that Al-Sn thin film is composed of an amorphous matrix and well-dispersed composite nanoparticles.Every particle contains an Al-riched area and a Sn-riched area.The Snriched area crystallizes and swallows up the Al-riched area gradually during heating through uphill diffusion of the Sn atoms.Based on the theoretical analysis and experimental results,an empirical model to explain the phase evolution process in the Al-Sn film was proposed.