Transport Mechanism of Fe Impurity During the Purification of Silicon by Electromagnetic Directional Solidification of Hypereutectic Si-Ti Melt

In the directional solidification process of the hypereutectic Si-Ti alloy, the transport mechanism of metal impurities plays a vital role in the purification of Si. However, the transport mechanism of the impurity elements in the directional solidification process of Si-Ti alloy has not been elucidated. Therefore, in this study, the segregation behavior and transport mechanism of the Fe impurity were determined by analyzing the microstructure of the Fe impurity compounds in the Si-rich layer and the backdiffusion and segregation thermodynamics of the solid/liquid interface. The results show that after the directional solidification of the hypereutectic Si-Ti alloy, the Fe impurity in the Si-rich layer is enriched at the grain boundaries of primary Si and TiSi2 by tau(5) phase segregation. The transport mechanism of the Fe impurity at the solid/liquid interface corrected the longitudinal distribution model of the Fe impurity, and the average error in the impurity distribution decreased from 41.86 to 18.19 pct. The segregation thermodynamics of the Fe impurity showed that the introduction of Ti enhanced the Fe impurity removal from Si, and the equilibrium segregation coefficient of Fe impurity decreased to 7.56 x 10(-7). The results of this study are highly significant for the purification of silicon using the hypereutectic Si-Ti alloy.