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Chapter II Solution Growth….
temperature controllers and also made easier to achieve solution temperature
near the room temperature. The solution is agitated either by mechanical
stirrer or by rotating seed holder. The fluid flow thus provided breaks up the
boundary layer of rejected solvent and leads to more perfect and faster
growth. This method often produces sufficiently large crystals. A very large
size, in terms of several kilograms of weight, KDP crystals have been grown
for LASER applications by this method [36].
Temperature difference methods are based on the formation of two
regions with different temperatures in the crystallizer. In one of them, the
substance which is always in excess in the form of the solid phase is
dissolved and in the other, crystal growth takes place. In this case two vessels
connected by tubes are usually prefered. The substance is dissolved in the
vessel with the higher temperature and the crystal is grown in the other. The
exchange between the vessel is achieved both by natural convection of the
solution and by stirring with a mechanical agitator. Due to natural convection,
the solution from the dissolution chamber moves along the upper tube into the
growth chamber and along the water tube in the reverse direction. The large
size crystals of various compounds can be grown successfully by this method.
Figure (2.9) shows the schematic diagram of this method.
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Figure: 2.9 Temperature difference method.
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