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Chapter II Solution Growth….
the seed to be present in the growth chamber during the filtration and
overheating operations, while at the same time it prevented the seed from
getting dissolved by under- saturated solution. When the solution process was
over and the solution had been cooled to the near saturation temperature, the
mercury seal was removed and the seed was exposed. This technique was
tested on DKDP crystal growth.
The effect of pH of KDP solution on the crystal growth has been
studied widely in order to grow good quality KDP crystals. KDP crystals at low
pH value (~ 1.5 pH) were grown by Gau et al [73]. In situ measurement of pH
and super- saturation dependent growth kinetics of prismatic and pyramidal
faces of KDP crystals were reported by Sharma et al [74]. The pH of solution
of KDP can be adjusted by using phosphoric acid.
The effect of different additives and impurities on the growth habit of
KDP crystals has been studied by large number of researchers. The effect of
meta phosphate, boric acid and quaternary ammonium cations of different
concentration on habit of KDP crystals was reported by Sun Xun et al [75].
Different impurities affect growth habit in different manner due to their varying
impurity adsorption mechanism. Maeda et al [76] used organic dyes (sunset
yellow FCF, brilliant blue FCF and sky blue) to study the growth rate and
morphology of (100) and (101) faces of KDP crystals. Dhanaraj et al [77]
added different molar ratio of K2CO3 in KDP and meta-stable zone widths of
KDP solutions were measured. The effects on meta-stable zone widths of
KDP by anions doping [78,79] and by trivalent transition metal ions (Mn +3 ,
Cr +3 ) have been reported by Lai et al [80].
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