( 1. 南京航空航天大學 材料科學與技術學院， 南京 210016;
2. 南京理工大學 材料科學與工程系， 南京 210094;
3. 清華大學 新型陶瓷與精細工藝國家重點實驗室， 北京 100084)
摘 要: 對YF3-CaF2燒結助劑體系的氮化鋁(AlN)低溫燒結過程中液相向表面遷移的現(xiàn)象和表層晶粒生長進行了研究， 同時分析討論了液相遷移的機制。 AlN低溫燒結過程中液相向表面的遷移， 有利于減少晶界相， 提高其熱導率。 然而， 液相向表面過量遷移和富集則導致了表層晶粒的異常生長， 坯體內部由于缺乏液相燒結助劑不能實現(xiàn)致密化， 這一現(xiàn)象也造成陶瓷基板的翹曲。 AlN陶瓷坯體在燒結起始階段的快速收縮和坯體內部AlN晶界兩面角大于72.5°都有助于液相向表面遷移。 低溫燒結后陶瓷表面的主要物相是AlN和Y2O3， Y2O3的出現(xiàn)并被碳熱還原生成可揮發(fā)的YN可能是表面呈現(xiàn)藍紫色的原因。 表面Y2O3的產(chǎn)生與釔鋁酸鹽(Y3Al5O12, Y4Al2O9)液相遷移至AlN陶瓷表面并與爐中碳氣氛發(fā)生碳熱還原有關。
關鍵字: 低溫燒結; 液相遷移; 晶粒生長; 氮化鋁
QIAO Liang3, ZHOU He-ping3
（ 1. College of Materials Science and Engineering,
Nanjing University of Aeronautics and Astronautics,
Nanjing 210016, China;
2. Department of Materials Science and Engineering,
Nanjing University of Science and Technology,
Nanjing 210094, China;
3. State Key Laboratory of New Ceramics and Fine Processing,
Tsinghua University, Beijing 100084, China）
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.
Key words: low-temperature sintering; liquid phase migration; grain growth; AlN
