Phase Diagrams

· Only repeated passes of the molten zone diminish the solid impurity level to less that can be achieved in the single freezing step.
· The diagram illustrates the effect of passing a single molten zone through a sample once, five, ten, and twenty times.
· In a practical zone refiner, several zones may be passed through the sample simultaneously, each separated from the its neighbor by a solid region.

From: Pfann, Scientific American 217 (1967) 63