Effect of cyclohexane diamine tetraacetic acid on micro morphology of rapidly grown potassium dihydrogen phosphate crystals

Abstract

Potassium dihydrogen phosphate (KDP) crystals were grown from aqueous solutions with different concentrations of cyclohexane diamine tetraacetic acid (CDTA) by the “point seed” rapid growth technique. The effects of CDTA on the surface micro morphology of KDP crystals were systematically studied by atomic force microscopy. The prismatic face growth rates of KDP crystals grown from various solutions were measured by a laser polarization interference system. The results shown that the steps became smooth after CDTA doping. When the doping concentration of CDTA is 100 ppm, the bunching of steps on the (100) face reduced dramatically and the step velocity increased obviously due to the complexation between CDTA and the metal impurities in the original solution. When the doping concentration of CDTA is 500 ppm, the excess CDTA adsorbed on the growth surface and impeded the step movement, leading to an increase in step bunching and reduction in step velocity compared with the situation of 100 ppm.