A space high temperature in situ observation instrument (SHITISOI) is dedicated to visualize and record the whole growth process of oxide crystal in high temperature melts and solutions. Model experiments using transparent liquids such as KNbO 3, Li 2 B 4 O 7+ KNbO 3 were chosen to investigate effects of interfacial mass transport in oxide crystal growth. For the scaling of the coupled velocity, heat and concentration fields in KNbO 3 crystal growth, a rotating growth process was performed and the widths of interfacial concentration, heat and momentum transition zones (The "boundary layers") are obtained, which are 7.5 × 10-3, and 8.6 × 10-2 and 4.4 × 10-1 cm , respectively. Hence one can expect that interfacial concentration gradient will be confined to a narrow layer and in region of major concentration change at the interface. In order to study a mechanism based on the interfacial mass transport resulting from hydrodynamics, the growth of KNbO 3 grain in high temperature Li 2 B 4 O 7 and KNbO 3 solution was studied. The result shows that the pivotal feature in the KNbO 3 crystal growth is the initiated by KNbO 3 solute surface tension gradient which is caused by the slow diffusion of KNbO 3solutes. Direct comparison of the model predictions and experimental observed phenomena demonstratre the predicitive capability of this model.
In situ Observation of Crystal Growth at High Temperature.
