Experimentally, it was observed that there were various morphologies of KNbO3 crystals in different regions of the melt of Li2B4O7, and KNbO3 mixture in Pt loop heater. Dendrites grew in the central area of the melt, the diffusive-advective region, in which the temperature gradient is negligible; whereas crystals with smooth surface were observed in the marginal area, the diffusive-convective region, with large temperature gradient. Based on the solute concentration over the KNbO3 crystal surface examined by electronic probe analysis, it was proved that the combinative effect of buoyancy and surface tension convection induced by temperature gradient enhanced the homogeneity of the solute concentration around KNbO3 crystals and thus their morphological stability.