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Zone melting (or zone refining, or floating-zone method, or floating-zone technique) is a group of similar methods of purifying crystals, in which a narrow region of a crystal is melted, and this molten zone is moved along the crystal. The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind ...
The molten zone carries the impurities away with it and hence reduces impurity concentration (most impurities are more soluble in the melt than the crystal). Specialized doping techniques like core doping , pill doping, gas doping and neutron transmutation doping are used to incorporate a uniform concentration of desirable impurity.
The methods involve heating polycrystalline material above its melting point and slowly cooling it from one end of its container, where a seed crystal is located. A single crystal of the same crystallographic orientation as the seed material is grown on the seed and is progressively formed along the length of the container.
Fractional freezing is a process used in process engineering and chemistry to separate substances with different melting points. It can be done by partial melting of a solid, for example in zone refining of silicon or metals, or by partial crystallization of a liquid, as in freeze distillation, also called normal freezing or progressive freezing.
The zone melting process developed by William Gardner Pfann was used to produce pure germanium, and subsequently float-zone silicon became available when Henry Theuerer of Bell Labs adapted Pfann's method to silicon. Types of materials that are usually refined: metals (see Refining (metallurgy) petroleum (see Oil refinery) silicon; sugar (see ...
William Gardner Pfann (October 27, 1917 – October 22, 1982) was an inventor and materials scientist with Bell Labs.Pfann is known for his development of zone melting which is essential to the semiconductor industry.
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In chemistry, fractional crystallization is a stage-wise separation technique that relies on the liquid–solid phase change. This technique fractionates via differences in crystallization temperature and enables the purification of multi-component mixtures, as long as none of the constituents can act as solvents to the others.