Optimal operating conditions for the rapid growth of KH2PO4 crystal by numerical simulation

Abstract

Numerical simulations of the turbulent hydrodynamics and concentration in the rapid growth of potassium dihydrogen phosphate (KH2PO4 or KDP) crystals have been performed. In this work, a quadratic power-law growth model is applied, concerning the mass transfer occurring at the crystal surface during the growth process under low supersaturations. The mass transfer boundary condition is discretized by using the Over-Relaxed approach. The effects of the growth temperature and rotation rate on surface supersaturation distribution and the diffusion layer are investigated, which are critically involved in the processes of surface morphological instability and inclusion formation. Due to the kinetic limitation, the response of different types of crystal surfaces to temperature varies, with a pyramidal surface about twice as high as a prismatic face. In addition, the contour map of the growth rate combined with the coefficient of variation (C.V) for various temperatures and rotation rates is used. Uniformity of surface supersaturation is provided by lowering the growth temperature and increasing the rotation rate. Furthermore, the criteria of crystal growth strategies are proposed to optimize the process parameters and obtain favorable conditions for crystal growth, thereby facilitating defect-free and high-quality crystal formation at an appropriate growth rate.