Effect of Convection and Solute Concentration on the Morphological Instability of KNbO_3 Crystal

The effect of diffusive-advection and diffusive-convection on KNbO3 crystal morphologies was studied respectively. Under diffusive-advection environment, the grain grows in dendritic pattern, while, in diffusive-convection, it grows in a pattern that the grain surface is smooth. Based on the fluid effect on solute concentration distribution near the grain, the influence of fluid effect on morphological stability was analyzed, it is proved that convection can enhance the morphological stability, this result agrees with the DMSI (Diffuseness of the Melt-Solid interface) theoretical calculation. The reason for that the grain size in diffusive-convective area is larger than that in diffusive-advective area was interpreted. Additionally, the solute concentration effect on KNbO3 grain morphologies was also studied qualitatively.