本研究在d50 = 240 nm的高純度α-Al2O3中，添加d50 = 18 nm 的θ- Al2O3，配置成含θ- Al2O3 0–30 wt%的θ/α- Al2O3的漿料。利用注漿成形法製成生坯，並於生坯中添加500 ppm的Mg2+，在真空條件下以1530-1700°C持溫1小時進行燒結。以BET、XRD、DTA觀察起始粉末平均粒徑、礦物相以及生坯於較低溫的相變熱反應。進行真空燒結後量測相對視密度、以SEM觀察微結構並計算平均晶粒大小以及量測光穿透率來比較添加θ-Al2O3細粒成分對粗粒α-Al2O3於高溫燒結的影響。
結果顯示全部的生坯相對密度都可以達到68%以上，最高的生坯密度76%出現在θ添加量為15 wt%的樣品。而從真空燒結試驗可以發現，添加θ-Al2O3對透光氧化鋁燒結體密度、晶粒尺寸，及光穿透率均有影響。由θ-Al2O3相轉換得之的細粒α-Al2O3會與原存在的粗粒α-Al2O3形成兩個燒結系統。粗細兩種粒體間的相互熱反應顯然較缺乏，因此添加θ-Al2O3確實會抑制原α-Al2O3的晶粒成長，但其抑制效果止於15-20 wt% θ添加量間，出現晶粒約9.0 μm（燒結條件：1700°C持溫1小時）。
研究結果也說明燒結體的透光率，於1530-1600°C間由燒結體密度主導，於1650°C-1700°C間則是燒結體之晶粒大小為影響關鍵。前者，15 wt% θ的樣品可以獲得最高的全穿透率64%以及直線穿透率6.52%，晶粒大小約7 μm。後者因抑制晶粒成長的結果，添加θ-Al2O3者存在較多的晶界影響，透光率相對較低。隨添加量減少，樣品晶粒尺寸達15 μm（0％ θ添加量），獲得最高的全穿透率85%，直線穿透率22%。根據本研究計算與綜合實驗結果推知，θ/α-Al2O3混合的最佳比例應介於15-20 wt%間。此時全穿透率78%以及直線穿透率15%，晶粒大小約11 μm。

The characteristics of processing green body and the followed sintering behavior during fabricating the translucent alumina using mixtures of α-Al2O3 powders (crystallite size 240 nm and chemical purity: Al2O3 99.9%) and θ-Al2O3 powders (18 nm and 99.9% ) were examined. Slurries prepared by mixing α-Al2O3 powders with 5, 10, 15, 20 and 30 wt % of θ-Al2O3 were used to produce green bodies by slip casting techniques. After dried, the green body was doped with 500 ppm Mg2+ and then sintered at 1530-1700°C for 1hr under vacuum status. It is found that the relative density of all green bodies can reach over 69%. The green with highest density of 76% was obtained when 15 wt % of θ-Al2O3 was added. The vacuum sintering results reveal that the slurries with θ-Al2O3 powders would affect the sintered density, grain size, and light transmittance properties of the translucent alumina. It is worthwhile to note that the finer-grained α-Al2O3 particles which transformed from θ-Al2O3 will experience a second sintering system coexisting with that of the original coarser-grained α-Al2O3. Although we didn't thoroughly observe the sintering phenomena of the two systems, the result shows the addition of θ-Al2O3 obviously slows down the grain growth of α-Al2O3. According to the calculations and experimental results, the optimal ratio of θ/α-Al2O3 mixtures should be between 15~20/85~80. In this case the alumina will show 78% total transmission, 15% in-line transmission, and its mean sintered grain size can be 11 μm.

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