以壓濾成形法製備透光多晶氧化鋁

Abstract

多晶透光氧化鋁由於其機械性質好、化學及溫度穩定性高，多應用在極端環境，如武裝玻璃、高溫爐視窗等。此外，若在其中作摻雜，則可拓寬其應用，有潛力發展成為雷射介質、閃爍體及發光二極體基板。本研究中，採用不同的成型法(乾壓成形、石膏模注漿成形及壓濾成形)，搭配空氣燒結，製備多晶透光氧化鋁，並比較製程對材料燒結行為、微結構以及直線透光度的影響。實驗結果顯示，由壓濾成形的生胚由於堆疊較均勻，在燒結後擁有最佳的透光度；而使用乾壓成形的生胚，生胚密度較低，且內部可觀察到許多裂縫，並在燒結後無法完全去除孔洞，因此透光性不好；以石膏模注漿成形之試片，推測由於模具碎片剝落並滲入生胚，導致燒結時發生異常晶粒成長，因此透光度也不佳。本研究進一步以壓濾成形法製備摻雜三價銪之透光多晶氧化鋁。發現所需緻密化之燒結溫度上升，且在摻雜量為0.1 at%、於1400C燒結的試片中，可觀察到EuAlO3的二次相析出。摻雜的試片透光度較未摻雜之多晶氧化鋁直線透光度低，且隨著摻雜量上升而下降。

Optical polycrystalline alumina (PCA) is a potential ceramic for the applications in harsh environmental conditions, such as armor window and window for high temperature furnace. It is mainly due to its good mechanical properties, chemical stability and thermal stability. By doping elements, the application can be further extended. In the present study, various forming methods such as die pressing, slip casting with a gypsum mold, and pressure filtration are adopted to prepare the green compacts. The results indicate that the specimens formed by pressure filtration exhibits optimum in-line transmission after sintering in air. Such result can be related to the uniform packing of green compacts. On the other hand, for the specimens formed by die pressing, some cracks are observed in the green compacts, and residual pores still exist after sintering. Debris from the gypsum mold is speculated to induce abnormal grain growth of alumina. Such abnormal grains can only be observed in the specimens formed by slip casting with a gypsum mold. As a result, the specimens formed by die pressing and slip casting are opaque after sintering. Besides, Eu3+ doped PCA is also prepared by pressure filtration. The sintering temperature required to densify the Eu3+ doped PCA specimens is higher. Second phase precipitates of EuAlO3 are detected in the specimen doped with 0.1 at% Eu3+. In-line transmission thus decreases with increasing doping levels.