Effect of amino acid additives on the growth and physical properties of potassium acid phthalate (KAP) crystals.

Single crystals of potassium acid phthalate (KAP) have been grown from aqueous solution by slow evaporation technique by adding l-alanine (LA), glycine (Gly) and l-tyrosine (LT) as additives. Powder X-ray diffraction studies confirmed the phase formation and amino acids doping into KAP crystals. The optical absorption studies reveal that the LA doped crystals possess less absorption of visible ray than the pristine, Gly and LT doped KAP crystals. Optical transmission is found to be low in LT doped KAP than in all the other crystals. TG-DTA studies show the decomposition temperatures to be 255 °C, 232 °C, 258 °C and 264 °C for pure, LA, Gly and LT doped KAP crystals respectively. SHG efficiency of LA doped KAP crystal was found to be 1.1 times (31 mV for KDP and 34 mV for LA doped KAP) that of potassium dihydrogen phosphate (KDP) crystal. This is much higher when compared to that of undoped KAP crystal (12mV). The grown crystals were also subjected to FTIR, microhardness and dielectric studies.