GROWTH-BEHAVIOR OF L-PYRROLIDONE-2-CARBOXYLIC ACID (L-PCA) SINGLE-CRYSTALS

Growth conditions to prepare large single crystals of L-pyrrolidone-2-carboxylic acid (L-PCA), a novel nonlinear optical organic material, have been intensively studied with an attempt for fabrication in optical devices. L-PCA single crystals of good optical quality having dimensions of typically approximately 2.5 x 1.5 x 1.5 cm3 were grown from aqueous solutions with seed crystals by a slow cooling method. They are chemically stable because molecules are hydrogen bonded to form three-dimensional networks in the crystal state. Further growth conditions to obtain large single crystals in a shorter time have been investigated by considering both mass balance equations and the kinetics for crystal growth. It was found that increasing the cooling rate in the later periods of crystal growth is advantageous for the purpose. The largest crystal was 17.5 g in weight, which was prepared in 6 days.