Ammonium dihydrogen orthophosphate (ADP) crystals were grown with amino acid materials L-arginine monohydrochloride and L-alanine as new additives in different molar concentrations. The metastable zonewidth of ADP solution with and without these additives was determined and compared. induction periods for nucleation as a function of supersaturation in different concentrations of additives were measured. Nucleation studies show that metastable zonewidth and induction period of ADP are enhanced by the addition of these amino acids. With increasing additive concentration, the growth Fate was found to increase. Amino acid added ADP crystals were grown from the aqueous solution with a simple apparatus that can be applied in certain forced convection configurations to maintain a higher homogeneity of the solution. Moreover, the addition of these amino acids improves the quality of the crystal and yields highly transparent crystals with well-defined features. The high-resolution X-ray diffraction (XRD) analysis reveals that the crystalline perfection of these amino acid doped ADP crystals is extremely good without having any internal structural grain boundaries and mosaic nature. The effect of additives on the growth, nucleation kinetics, structural, optical and mechanical properties has been investigated. (C) 2008 Elsevier B.V. All rights reserved.