Study on the behavior of impurities in the process of refining indium by zone melting

In this paper, the migration and distribution behavior of Cu, Fe, Si and Mg impurities in the process of preparing high purity indium by the zone melting method in an argon atmosphere was studied. The temperature distribution at the location of the indium samples during the zone melting process was simulated using Fluent software, and the temperature required to maintain the stability of the molten zone length of the samples during the experiment was determined to be 162 °C. The effects of moving speed (0.5 and 1.0 mm/min) of the molten zone and the number of zone melting times (5, 10, 15, 20 times) on the migration and distribution of Cu, Fe, Si and Mg impurities in In were systematically studied. When the moving speed of the molten zone is 0.5 mm/min, after 15 times of zone melting, the contents of impurities Cu, Fe, Si and Mg in the middle of the sample (i.e., 140 mm from the head end) are 0.1208, 0.007, 0.0615 and 0.0211 mg/kg, respectively. The removal rate of Cu, Fe and Si are higher than 80 %, and the removal rate of Mg is higher than 70 %. The experimental results show that the removal effects of Cu, Fe and Si impurities by the zone melting method are obvious, and these impurities are easier to be removed than Mg. By optimizing the moving speed of the molten zone and the number of zone melting times, high purity In with lower content of Cu, Fe and Si impurities was prepared.