对流效应和溶质浓度对KNbO3晶体界面形貌稳定性的影响

研究了在不同对流形态对KNbO3晶体生长形貌的影响。在温度梯度较小的扩散-平流区域，晶体以枝蔓晶的形态生长；而在温度梯度的较大的扩散-对流区域，生长出的晶体呈现光滑晶面。通过测定不同区域KNbO3晶体界面附近的溶质浓度分布，从对流效应降低晶体界面附近的溶质浓度分布的不均匀性的角度研究了对流效应对晶体界面形貌稳定性的影响，证明对流效应提高了晶体界面形貌稳定性，与晶体界面弥散度的理论计算相一致。同时解释了扩散-对流区域的晶体尺寸大于扩散-平流区域的晶体尺寸的原因。观察并定性地解释了不同溶质浓度KNbO3形成不同的界面非稳定形貌，当KNbO3重量百分比为20wt%时形成骸晶，30wt%时形成枝蔓晶。

Effect of Convection and Solute Concentration on the Morphological Instability of KNbO3 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.