Download Organic Crystals, Germanates, Semiconductors by L. N. Demianets, G. A. Emelchenko, J. Hesse, N. Karl, A. N. PDF

By L. N. Demianets, G. A. Emelchenko, J. Hesse, N. Karl, A. N. Lobachev, H. Maier (auth.)

1.1 Preface natural chemistry had its foundation in chemical compounds that are synthesized by means of dwelling cells. those chemical compounds encompass molecules whose skeletons are outfitted up of carbon atoms. the rest valences are attached with ligands akin to hydrogen, halo­ gens, -OH,==O, -NH . a number of the skeletal carbon atoms may be changed through non­ 2 metals equivalent to oxygen, nitrogen, or sulfur {"heteroatoms"}. it truly is attribute for the residing international, to not be in a crystalline country. but it is feasible to acquire unmarried crystals from many natural compounds either one of typical and artificial starting place. For a couple of years the physics and chem­ istry of those crystals have inspired basic learn on a speedily starting to be scale. the nice number of attainable natural constructions {as in comparison to inorganics} opens up a wide box of recent fabrics and of novel fabric houses; for prior literature reports and information compilations see 1-40) and Chap. 6. The paintings of manufacturing solid and natural natural unmarried crystals has constructed hand­ in-hand with the ever transforming into specifications of easy learn, coming up from its curiosity in basic interactions within the reliable country. Interactions take place themselves in a truly particular means via power transfer.

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Extra info for Organic Crystals, Germanates, Semiconductors

Example text

The anthracene Diels-Alder adduct is removed from the solution by extraction with aqueous potassium hydroxide solution. "Potassium (or sodium) fusion" is amethod where molten organic compounds react selectively with molten potassium metal under vacuum. It is useful for impurity molecules with sites or side groups which lead to the formation of non volatile potassium salts such as thionaphthene or /3-methylnaphthalene. Both of these impurities are contained in ,"natural" naphthalene. Potassium fusion may also be useful where final reaction products are formed which have more favourable distribution coefficients at zone refining or where an impurity is selectively or at least preferentially decomposed.

To avoid redistribution of the impurities, only remelting of one zone length is permissible and this zone should travel in the same direction as during zone refining. Therefore Bridgman growth immediately in the zone refining tube seems feasible only with the reverse zone refming technique. 4) by using zone refining tubes provided with a cone (cf. Fig. 21 a) at the "filled" end for seed formation and applying a reduced speed for the last zone. However, a separate crystal growth step is generally preferable.

The zone refming (glass) tube is inserted; it is transported in the usual A-B II uijUff B5 Fig. 22. Horizontal reverse multistage zone refiner; after Benz et al. l l l ) 31 N. Karl 1/ =::::::: =::J 1 ~ a r~: : b 3 1 2 , L :::::: cr~: : :::::: 1 : : J dL~=:::J Fig. 23 a-d. Several versions of generating a periodic temperature profile for zone refining, see text l12 ) way as described above and should be stirred by intermittent rotation. The metal tube is heated as a whole by running a low voltage high current along it.

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