有鑑於現階段工業上製造YAG粉末之方式，大部分使用Y2O3與α-Al2O3以固態反應法1600 ℃合成，反應過程一般會依序出現中間相YAM及YAP。因此本研究欲減低生產時所需之能耗，以低溫、經濟及環保之方式，藉由添加晶種合成YAG純相粉末。本實驗擬添加0、0.2、0.4和0.8 wt%之YAG晶種並造粒後，再施以熱處理觀察其相轉換。結果以0.2~0.4 wt%晶種添加量為較佳，約在1300 ℃即可獲得純相YAG，較工業上所需之高溫降低300 ℃。未添加晶種之系統生成之中間相如前人所觀察到之YAM及YAP，且需在大於1400 ℃才可獲得純相YAG；添加晶種之系統發現有促使YAM低溫大量生成與使YAP相生成不明顯的現象。添加與未添加晶種系統，生成YAG所需活化能分別約為282 kJ/mol以及1231 kJ/mol，證實添加晶種可以降低生成YAG之活化能，兩者之差值應為減少了YAG成核與減低YAM及YAP生成活化能。添加晶種可能使相變反應機制改變為：YAM →YAP（少量且固定）→ YAG。實驗另以添加0.2 wt%晶種條件，改變研磨混合時間觀察起始氧化物之混合均勻度與YAG的生成關係。結果以研磨混合2天之系統在1200 ℃即可合成純相YAG粉末，相較於較短混合時間者，顯示研磨混合時間的延長，可提高起始成分的混合均勻度，而有利於低溫生成YAG粉末。

Due to the fact that the present method of producing YAG powder is performed by solid state reaction using Y2O3 and α-Al2O3 as starting materials at 1600℃,the intermediate phases of YAM and YAP will show up in sequence during the process. This research tends, by seeding, to synthesize the phase-pure YAG powder at lower temperatures with a way of energy-saving, low cost, and pollution free. In this study, the formation temperature of YAG particles is lessened by adding YAG seeds (0, 0.2, 0.4 and 0.8 wt%) in the slurry composed of Y2O3 and α-Al2O3 particles. After spray drying, granules were heated and the phase evolution was examined. It turned out that the addition of seeds between 0.2 to 0.4 wt% is better than the others: the single phase YAG powder is obtained at about 1300℃ and whose reduced temperature is 300℃. Without seeding, the intermediate phases, YAM and YAP, were observed and phase-pure YAG powder only could be obtained at temperatures larger than 1400℃. With seeding, formation of YAM was promoted while YAP was unobvious. The activation energies for YAG formation are 282 and 1231 kJ/mol with respect to the powder system with and without seeds. Indeed, seeding can lower the activation energy of YAG formation. The mechanism of phase transformation may be changed by seeding and undergoes as such way: decreasing activation energies for YAG nucleation and YAP formation（YAM→ a fixed modicum of YAP → YAG）. The relationship between homogeneity of starting oxides and formation of YAG crystallites was also observed by altering the duration of mixing of samples with 0.2 wt% seeds. As a result, the 2-day system can synthesize a single phase YAG powder at 1200℃. Compared to the powder system which has shorter time of mixing, it reveals that the homogeneity of incipient ingredient can be raised by prolonging the mixing time, and it is conducive to form YAG crystallites at lower temperatures.

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