中文摘要
以軟水鋁石(boehmite)作為前導物來生產氧化鋁微粉時，其相轉換歷程，一般為： boehmite g d q a (最終穩定相)。由於 q–Al2O3 相轉換為 a–Al2O3 過程中，常伴隨著a–Al2O3 晶粒的急速成長，因此也喪失了其毫微米粒子的特性。本研究以結晶化學的方法，亦即添加 Fe3+ 離子來錯開晶粒成長與相轉換溫度，希望 Fe3+ 離子進入氧化鋁結構中，改變其結構能( structure/lattice energy )，進而改變 q 至 a 相氧化鋁相轉換溫度，期望在粉末燒結期間，能錯開 晶粒快速成長溫度與相轉換溫度，使得氧化鋁晶粒在燒結過程中，不僅晶粒成長控制容易，且更可促進燒結緻密。
本研究以商用boehmite為起始原料，添加1 mole% 及2.5 mole%的Fe3+ 離子，接著以1050℃ 持溫1小時得到所需之燒結用粉末，其主相為 q–Al2O3 ，晶粒控制在約22 nm 左右。粉末經去凝聚後，以40 MPa單軸乾壓成形，再以200 MPa 進行CIP (cold isostatic pressing) 均壓成形得所需之生坯。分別以 1100℃、1200℃、1300℃、1400℃、1500℃均不持溫進行燒結；並藉由熱差分析、X光繞射分析、燒結收縮量測、微結構觀察、孔隙大小分佈量測，深入探討不同Fe3+ 離子添加量對燒結情形的影響。分析研究成果得到以下結論：
1. 添加鐵離子會使 q 至 a 氧化鋁相轉換溫度降低，且隨著添加量的增加有愈下降的趨勢。
2. 在相同的燒結溫度下，隨著鐵離子添加量的增加，燒結體緻密化程度也相對較高，但對晶粒成長的控制並不明顯，不過在相對密度近 97% 時，晶粒大小仍可控制在 1 mm 以下。
3. 因鐵離子的添加，不僅可使 q 至 a 氧化鋁相轉換溫度降低，更促進相轉換的發生，因而改變了燒結收縮速率，使其較易達到 a 氧化鋁 燒結緻密。

ABSTRACT
In the process of phase transformation from boehmite to a-Al2O3, the main phases are: boehmite g-Al2O3 d-Al2O3 q-Al2O3 a-Al2O3. Because the phase transformation of q-Al2O3 a-Al2O3 is accompanied with growth of a-Al2O3 crystallites, it will lose the sub micron - particle’s characteristics. The study hopes to change aluminum’s structure energy and the q to a phase transformation temperature by adding small amount of iron ion to alumina lattice site that won’t change its structure, and at the same time make the rapid grain growth occurred at different temperature, in order to control the growth of a-Al2O3 crystallites and enhance the sintering activity.
The starting material was commercial boehmite with addition of 1 mole% and 2.5 mole% Fe3+. After calcining at 1050℃/1 h, raw powder transferred to q phase and its crystallite size is about 22 nm. After de-agglomeration, they were first uniaxially pressed at 40 MPa and then cold isostatically pressed at 200 MPa. To study microstructure evolution during sintering of the compact, heat treatment was carried out at temperature from 1000℃ to 1500℃. Differential thermal analyzer (DTA), X-ray diffractometer, scanning electron microscope (SEM), and mercury penetration porosimeter were used to characterize their thermal behavior, the quantity of phase transformation, particle size, pore size distribution, density, and the changes of microstructure. Conclusions of this study are :
1. By addition of Fe3+, it can decrease the q to a phase transformation temperature. The more amount of Fe3+ addition, the lower the transformation temperature and the faster the transformation rate.
2. At the same sintering temperature. The more amount of Fe3+ addition, the higher densification of sintered bulks. But crystallite growth was still fast. Relative density reached 97%, and crystallite size was ＜1mm.
3. With the addition of Fe3+, it can not only decrease the q to a phase transformation temperature but also enhance the sintering shrinkage rate to achieve densification of a-Al2O3.

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