Physical Geology: The Growth Of Crystals

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Physical geology: The Growth of Crystals

Fundamental aspects of crystal growth technology was derived from early studies of crystallization in the 18 th and 19 th century with the development of thermodynamics in the late 19 th century (Gibbs, Arrhenius, Van't Hoff), and with the development of nucleation and growth theory and the role of transport phenomena in the 20 century. Undercooling, supersaturation and crystallization heat was already recognized Fahrenheit (1724) and Lowitz (1795). The corresponding metastable region, the reality is different supercooled solutions, has been evaluated and characterized by Ostwald (1893/1897) and Myers (1906), whereas the effect of friction on the width of the area Ostwald-Myers was told by Jung (1911 / 1913). Influence to incite the metastable region plays an important role in mass crystallization of salt, sugar and various chemicals: yet it is not appreciated in theory. Tammann (1925) investigated the nucleation and crystallization rates mainly in the glasses, and Volmer and Weber prepared the base for the nucleation theory. Crystal surface with steps and kinks Kossel (1927) allowed the Stranski and Kaischew (1934) to describe the separation of quartz as repeating the steps as the cornerstone of the first theory of crystal growth. With the understanding aspect of the formation as a function of the entropy of fusion (Jackson, 1958), the density of bonds in the crystal structure (Hartman and Perdok, 1955), the function of screw dislocations, as relentlessly causes a step in the formation of growth hillocks (Frank, 1949), and the generalized theory of Burton, Cabrera and Open (1951), many of the phenomena of growth can be explained.

In crystal growth from liquid intermediate (molten, a response of the gas phase) mass transfer phenomena also play a significant role, as it was early recognized Rouelle (1745) and Frankenheim (1835). The level of diffusion boundaries are determined by Noyes and Whitney (1897) was used in the Nernst equation of growth (1904) and confirmed by measurements interferrometric giving profiles around growing crystals Berg (1938) and others. Forced convection was determined to be beneficial for the diffusion-limited growth Wolfe (1886), Krueger and Fink (1910) and Johnson (1915) for open schemes with stirrers, and the smooth kindling in sealed containers can be achieved with the accelerated crucible rotation technique (ACRT) (Scheel, 1971). Growth without the inclusion of the crystals from the melt can be achieved by adhering to the principles of the diffusion of hypothermia in Ivantsov (1951) and the constitutional supercooling Tiller Jackson Rutter-Chalmers (1953). The formation of inclusions, ie, the instability growth can be stopped in the growth of replies adequate flow against or along the edges of the crystal: Carlson (1958) developed an empirical idea, which was used Scheel and Elwell (1972) to obtain the maximum stable growth rate and are optimized Programming supersaturation to obtain large crystals without inclusions.

Fig. 1. Stages of flame-fusion development of high-melting oxides, schematic: (a) formation of sinter cone and centered melt droplet up on alumina rod. The powder supply and the hydrogen-oxygen flame are adjusted; (b) to allow growth of the neck from ...
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