Growth rate hysteresis of a potassium dihydrogen phosphate (KDP) crystal in the presence of traces of impurity

The growth rate of the (1 0 0) face of a single potassium dihydrogen phosphate (KDP) crystal was investigated in the presence of traces of chromium (III) up to 5 ppm in a flow cell at different rates of changes of supercooling (±0.1 and ±0.2 °C/min). Hysteresis in crystal growth rates in the presence of chromium (III) was induced by decreasing and increasing the supercooling. The growth hysteresis is described qualitatively by a mathematical model considering the pinning mechanism of Cabrera and Vermilya, the two-dimensional Gibbs-Thompson effect on step movement and by assuming slow adsorption of impurity species on the crystal surface.