What are typical freezing rates for inorganic materials in zone refining?

For inorganic materials, typical freezing rates in zone refining range from 0.5 to 30 centimetres per hour (0.2 to 12 inches per hour).1

While these rates are common, it is important to note that the effectiveness of the process depends on the freezing rate. At moderate rates within this range, the effective distribution coefficient of impurities is influenced by the liquid-solid interface dynamics. If the freezing rate becomes too rapid, the distribution coefficient may approach unity, which prevents effective purification and can lead to a dendritic or branching interface shape.1