Phase Diagrams

Zone Refining

· High purity silicon is required for the semiconductor industry and the needed levels cannot be reached by chemical methods alone.
· Zone refining techniques for purification use the solid-liquid phase transition to purify the solid by expelling impurities to the remaining liquid.
· The phase diagram shown indicates the difference in impurity content between the liquid and solid at a given solidification

From: Ashby & Jones, "Engineering Materials 2," Pergamon (1986)

temperature. The distribution coefficient, k, must be less than 1 for the technique to work.