The convective effect on the morphological instability of KNbO3 crystals

Experimentally, it was observed that there were various morphologies of KNb O3 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 diff usive-advective region, in which the temperature gradient is negligible; wh ereas 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 s urface tension convection induced by temperature gradient enhanced the homo geneity of the solute concentration around KNbO3 crystals and thus their mo rphological stability. (C) 2001 Elsevier Science B.V. All rights reserved.