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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.
In metallurgy, refining consists of purifying an impure metal. It is to be distinguished from other processes such as smelting and calcining in that those two involve a chemical change to the raw material, whereas in refining the final material is chemically identical to the raw material. Refining thus increases the purity of the raw material ...
Coring happens when a heated alloy, such as a Cu-Ni system, cools in non-equilibrium conditions. The center of each grain, which is the first part to freeze, is rich in the high-melting element (e.g., nickel for this Cu–Ni system), whereas the concentration of the low-melting element increases with position from this region to the grain boundary.
In 1952, Pfann published the revelatory article "Principles of Zone-Melting" in the Transactions of the American Institute of Mining, Metallurgical, and Petroleum Engineers. [5] This article applied zone melting in two industrial processes: purification of a solvent material (called zone refining), and production of a uniform distribution of a ...
The Czochralski method, also Czochralski technique or Czochralski process, is a method of crystal growth used to obtain single crystals of semiconductors (e.g. silicon, germanium and gallium arsenide), metals (e.g. palladium, platinum, silver, gold), salts and synthetic gemstones.