Effect of applied electric current on impurity transport in zone refining

The article presents the results of a combined numerical and experimental study of the effect of an applied current on impurity transport in a zone refining system. The three-zone system previously developed was used for experiments and also for numerical simulations. An impurity (selenium) with a segregation coefficient close to unity was considered in the numerical simulations for tellurium (Te) and cadmium (Cd) melts, but the experiments were only carried out for the Te system. In the model, a single molten zone was considered for simplicity. Both the simulation and experimental results have shown that under the experimental and modeling conditions considered in this work, the contribution of electromigration to the selenium impurity transport in Te is not significant. However, the numerical simulations indicate that electromigration may enhance the impurity transport in Cd if a sufficient electric current density can be applied. This is due to the higher electric conductivity of Cd compared with that of Te.