【摘要】 对YF3 CaF2烧结助剂体系的氮化铝(AlN)低温烧结过程中液相向表面迁移的现象和表层晶粒生长进行了研究,同时分析讨论了液相迁移的机制。AlN低温烧结过程中液相向表面的迁移,有利于减少晶界相,提高其热导率。然而,液相向表面过量迁移和富集则导致了表层晶粒的异常生长,坯体内部由于缺乏液相烧结助剂不能实现致密化,这一现象也造成陶瓷基板的翘曲。AlN陶瓷坯体在烧结起始阶段的快速收缩和坯体内部AlN晶界两面角大于72.5°都有助于液相向表面迁移。低温烧结后陶瓷表面的主要物相是AlN和Y2O3,Y2O3的出现并被碳热还原生成可挥发的YN可能是表面呈现蓝紫色的原因。表面Y2O3的产生与钇铝酸盐(Y3Al5O12,Y4Al2O9)液相迁移至AlN陶瓷表面并与炉中碳气氛发生碳热还原有关。更多还原

【Abstract】 The formation and the migration of the liquid phase towards the surface of AlN ceramics produced via low-temperature sintering of mixture of AlN, YF₃ and CaF₂ powders, as well as the mechanism and the effects of this phenomenon in the final products were experimentally investigated. The liquid phase migrates towards the surface and solidified at the grain boundaries during cooling. Therefore, dense surface and porous bulk microstructure are obtained, which causes warping effect. The rapid shrinkage occurs at the beginning of sintering and the poor wetting of the liquid at the grain boundaries as long as the dihedral groove angle is over 72.5° favor migration. The main phases at the surface are AlN and Y₂O₃, causing bluish coloring of the surface. However, Y₂O₃ probably resulted from carbothermal secondary reaction of yttrium aluminates (Y₃Al₅O₁₂, Y₄Al₂O₉) migrates at the surface of AlN with carbon from the graphite-heating element under nitrogen atmosphere.更多还原