Abstract: 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.

Key words: KNbO₃, morphological instability, dendrite