Nucleation kinetics and growth of high-quality DAST crystals with the aid of activated carbon as the adsorbent to micro-crystals in solutions

Growth of highly nonlinear optical 4-N, N-dimethylamino-4'-N'-methyl stilbazolium tosylate (DAST) crystals had been carried out with the addition of activated carbon into the methanol solutions. The metastable zone width and induction period were experimentally determined for the modified growth conditions. Nucleation kinetics and fundamental growth parameters such as surface free energy, critical radius and critical free energy change were also evaluated according to the experimental data. The observations indicated that adsorption to tiny nuclei by activated carbon favored to improve the stabilities of growth solutions. Twin-free seeds and platelets with good qualities were effectively obtained under the optimized conditions. The introduction of activated carbon into growth solutions favors the growth of bulk DAST crystals at a relatively high rate, and high quality bulk crystal with dimensions of 8.3 x 8.4 x 2.5 mm(3) was obtained under the optimized growth conditions. In addition, the obtained DAST crystals with well-developed (0 0 1) and (0 0 -1) faces facilitate the direct utilization for electro-optic and nonlinear optical applications. The grown crystals were also characterized by the micro-hardness test, optical transmission and etching investigation. (C) 2011 Elsevier B.V. All rights reserved.