Phase Diagrams

· The diagram compares the zone refining configuration to that of a normal freezing process.
· In the normal freezing process, the material is initially all in the liquid phase and freezes from one end. Impurities are displaced from the solid into the liquid phase according to their segregation coefficient.

· In zone refining, a small, local molten zone is passed through an initially solid material, impurities being segregated to the liquid at the freezing interface.

From: Pfann, Zone Refining, Scientific American 217 (1967) 63