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Zone melting technique

Semiconductor and Solar Cells. High purity (up to 99.9%) antimony has a limited but important appHcation in the manufacture of semiconductor devices (see Semiconductors). It may be obtained by reduction of a chemically purified antimony compound with a high purity gaseous or soHd reductant, or by thermal decomposition of stibine. The reduced metal may be further purified by pyrometaHurgical and zone melting techniques. [Pg.198]

In addition to the above, purification of /V-methylacetamide can be achieved by fractional freezing, including zone melting, repeated many times, or by chemical treatment with vacuum distn under reduced pressures. For details of zone melting techniques, see Knecht in Recommended Methods for Purification of Solvents and Tests for Impurities, Coetzee Ed. Pergamon Press 1982. [Pg.287]

Elements dissolved in boron influence its crystal structure. Dissolved impurities also influenee the physical and chemical properties of boron, especially the electrical properties, because boron is a semiconductor. Preparation of solid solutions in jS-rh boron requires a careful choice of crucible material. To avoid contamination, boron nitride or a cold, coinage-metal crucible should be used or the levitation or floating-zone melting techniques applied. [Pg.250]

As shown by Fig. 22.16, the concentrations of solute atoms are significantly reduced in the material that is solidified early in the solidification process when k < 1. One-dimensional plane-front solidification can therefore be used as a method of purification. However, purification is carried more effectively out by modifying the process and adopting a zone-melting technique. [Pg.546]

Zone melting techniques are slow, very slow. Rates of zone movement vary from 1 to 20 cm/h. Figure 2-8 shows a more efficient arrangement. Once the heated zone has refrozen there is no reason why it can t be remelted. In this case, three heaters are used, and the charge is moved. Figure 2-9 shows a helical type where you can get many molten zones. This is more appropriate for organic compounds, which are lower melting than metals. [Pg.17]

The oxide is reduced with hydrogen gas at 650°C and the metal powder is melted at 1100°C. Small germanium ingots are cast as rods in a protective gas atmosphere. Semiconductor-grade germanium is produced by the zone melting technique, as described in Chapter 40 Silicon. [Pg.930]

Richman et al. (1967) have pointed out the following advantages of normal freezing over the zone melting technique ... [Pg.410]


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See also in sourсe #XX -- [ Pg.31 ]




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