Improvement of growth habit and optical properties of rapidly grown KDP crystal by adding diethylene triamine pentacetate acid in growth solution

By altering the concentration of a new additive - diethylene triamine pentacetate acid (DTPA) in the growth solution, a series of KDP crystals were obtained by the point seed rapid growth method. The growth rates up to about 20mm/day. Effects of DTPA on the growth habit and optical properties of these as-grown KDP crystals were investigated. The results reveal that, with the increase of DTPA concentration in growth solution, the contents of impurity metal ions incorporated into crystal and aspect ratio of crystal morphology were both decreased gradually, while the UV transmittance of crystal was enhanced continually. In the presence of moderate concentration of DTPA (100-200ppm), the solution stability was increased and optical properties of crystal (including optical homogeneity, light scattering and laser damage threshold) were all improved. However excessive doping (>500ppm) has opposite effects. The impact mechanism was also analyzed combining with the structure of KDP crystal and chemical characteristics of DTPA molecular.