Long-time growth rate changes of sodium chlorate, potassium dihydrogen phosphate, and rochelle salt crystals independent of growth conditions

Abstract

Results of investigations of the changes in growth rate inherent to crystals (i.e., independent of macroscopic external conditions) during a 15-h growth period are presented. The results of the investigations regarding the time evolution of the growth rate dispersion are also presented. The majority of the investigations were carried out with sodium chlorate crystals, and several experiments were carried out with potassium dihydrogen phosphate (KDP) and Rochelle salt crystals. It was found that, for the majority of the crystals, the main changes in growth rate occurred in the initial growth stage, which extended to for up 4 h. These growth rates probably slowly decrease toward the end of the growth run. Some of the very high initial growth rates that decreased during the initial growth period were followed by relatively high intermediate growth rates for the next few hours and then subsequently decreased. The growth rates for the majority of crystals probably gradually decreased after 15 h of growth. The results obtained show that these changes, which have not previously been taken into account, should be included in the interpretation of growth rate changes affected by various parameters (supersaturation, temperature, fields, stress, impurities, etc.). The obtained results could improve the current crystal growth theories, which are based on the design of specific growth conditions that result in a target product. © 2011 American Chemical Society.