LAUSR

The surface tension driven convection, together with the rotating crystal growth process of potassium tantalate niobate (KTa1-xNbxO3, KTN) crystals from unstirred melt has been carried out in a high temperature in-situ observation system. The streamline of the stable convection is found to be in the form of a double loop axially symmetric vortices, which causes the rotation during KTN crystals growth process. The effect of surface tension convection on interfacial heat, mass and momentum transfer are investigated experimentally. The dimensionless parameters of the three transports are calculated. For KTN crystals, velocity and temperature boundary layers are pointless. Solute transfer is the main form of interface transport during crystal growth process. The effect of Nb content x on boundary layer thickness is discussed. There is a critical Marangoni Number Mac∼60. When Ma>Mac, the concentration boundary layer becomes thinner with the increase of x as a result of weakened segregation effect. When Ma>Mac, a thicker boundary layer emerges due to slower growth velocity under higher Nb contents. When Ma∼Mac, the influence of the two is comparable and the boundary layer can maintain a relatively steady value under different components.