无机材料学报2000，Vol.15Issue(5)：769-776,8.
高温氧化物晶体界面非稳定性研究
Polyhedral Instability of High-temperature Oxide Crystal
摘要
Abstract
Model experiments were designed in order to obtain more reliable data on the diversity of some crystal forms and polyhedral instability-skeletal and dendritic growth in high 妕emperature solution growth. These experiments were performed by High Temperature In Situ Observation Technique. Most of our investigations on high temperature solution growth were performed in a loop-shaped Pt wire heater, having a diameter about 2mm. The Pt wire (0.2mm) was used to heat and suspend the solution. A mixture of KNbO3 (20wt%) and Li2B4O7 was chosen for growth. Rapid growth, and hence diffusion mechanism limitations can result in various imperfections; such as the formation of cavities in the facets, skeletal and dendritic patterns. Quenching experiments were designed to distinguish some KNbO3 crystal forms, and the morphology of KNbO3 crystals grown in Li2B4O7 solution was studied with a scanning electron microscope. In all cases, when the crystal is nucleated near air/solution interface, it looses its polyhedral stability. The thickness of this shape destabilizing solution layer is about 60. The morphologies of crystals observed by a scanning electron microscope, vary in the layer from polyhedrons to dendrites. Anisotropic aspects of skeletal and dendritic structures reflect the cubic nature of KNbO3 as well as the fact that instabilities amplify and propagate along the four (110) crystal edges. The side branches in the four (110) directions provide convincing evidence for the growth shape anisotropy. The value of the critical size for loss of polyhedral stability is about 10. In contrast, the stable shape of the faceted crystal is generally retained with adequate reproducibility for all crystals grown in the solution beneath the shape-destabilizing layer. The polyhedral crystal growth processes were in-situ observed and recorded by HITISOT. The thermoconcentrational driven convection (i.e.microconvection) around the solid-liquid interface of the polyhedral crystal was also visualized.关键词
高温氧化物/界面非稳定性/KNbO3/高温实时观察装置/扫描电镜Key words
high-temperature oxide/polyhedral instability/KNbO3/high-temperature in situ observation device/scanning electron microscope分类
数理科学引用本文复制引用
金蔚青,蔡丽霞,潘志雷,苗宇..高温氧化物晶体界面非稳定性研究[J].无机材料学报,2000,15(5):769-776,8.基金项目
国家科学技术委员会攀登资助项目(95-预-34)? （95-预-34）
国家自然科学基金重点项目(59832080) （59832080）
