This contribution provides a review of effects of impurities on crystal growth.
Impurity can be any substance other than the material being crystallized.
Therefore even the solvent from which the crystals are grown can be considered to be an impurity. When impurities are added specifically to produce a desired morphological effect they are referred to as additives. The presence of impurities or additives in a crystallization system can have a radical effect on crystal growth, nucleation, macrostep formation, agglomeration and on the uptake of foreign ions in the crystal structure. Nevertheless, the specific impurity may effect differently on different crystallization chemical. The influence of impurity or additive can be caused by various mechanisms, such as of the presence of metal ions, and of tailor-made and multifunctional additive.