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Chapter II Solution Growth….
Rapid growth of KDP crystals has been obtained by various workers.
Linear high speed growth of 80 mm/day was obtained by computer controlled
mechanism by Minagawa et al [68] and earlier than this a rapid growth of over
50 mm/day was reported by Nakatsuka et al [69] for KDP crystals. Recently, a
movie of KDP crystal growth weighing 800 pounds is put on internet in
Youtube [70], which uses six feet high tank containing one ton supersaturated
solution of KDP. By using the turntable tank to rotate the crystal it was
possible to grow the crystal in two months, otherwise, it would have taken two
years in the conventional technique.
Two modifications have been proposed to avoid spurious nucleations
and seed isolations. Karnal et al [71] suggested modification in the growth set
up against spurious nucleation. Stability of the solution against spurious
nucleation plays a dominant role in the growth of crystals at high growth rates
requiring high levels of super saturations. If any spurious nucleation takes
place during the growth, it becomes practically impossible grow very large
size crystals. An indigenous nucleation-trap crystallizer was developed by the
authors to trap any unwanted nuclei and particles that appeared and settled at
the bottom of the crystallizer. Any particles and nuclei nucleating during the
growth were forced into the nucleation trap (or well) and, subsequently, by
manipulating the temperature of the well, those could be arrested. This was
successfully demonstrated for DKDP crystal growth. Moreover, a novel seed
isolation technique was proposed by Karnal et al [72]. In this method a
mercury seal was developed that facilitated the processing of the solutions
with immersed seed. This technique allowed a seed crystal to be introduced
into the crystallizer prior to the processing of the solution and hence allowed
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