本研究第一部分以化學沉澱法製備氧化鉍 (Bi2O3) 粉末，使用硝酸鉍 (Bi(NO)3) 作為前驅鹽 (precursor) 提供鉍離子，氫氧化鈉作為沉澱劑提供氫氧基合成氧化鉍。實驗中，改變鉍離子濃度以及鉍離子與氫氧化鈉之化學計量比例 (NaOH/Bi3+)，探討對於氧化鉍粉末結晶相與顯微結構之影響。XRD 分析結果顯示，當 NaOH/Bi3+ = 5，可在室溫下直接合成出單一相單斜結構之氧化鉍粉末，若再增加氫氧化鈉的計量，會產生氫氧化鉍 (Bi(OH)3) 之結晶相。SEM 分析結果得知，化學沉澱法合成之氧化鉍為微米級粉末，其形貌呈針狀。若增加 NaOH/Bi3+ 會使得氧化鉍粉末形貌之長寬比 (aspect ratio) 有變小的趨勢，且會促進晶粒之成長；增加反應系統中的鉍離子濃度，氧化鉍粉末形貌長寬比也會隨之變小，且同樣會促進晶粒成長。TEM 分析結果顯示，經由化學沉澱法所合成之氧化鉍為單晶 (single crystal)，且針狀粉末在成核成長過程中，其從優生長方向為 [0 0 1]。
　　第二部分以尿素沉澱法製備奈米級氧化鉍粉末，XRD 分析結果顯示，以尿素作為沉澱劑提供碳酸根，經由水熱反應會先得到中間相碳酸氧鉍 (Bi2O2CO3)，然後經過熱處理去除碳酸根，可得到奈米級氧化鉍粉末。由 SEM 分析發現，鉍離子濃度為碳酸氧鉍粉末粒徑大小改變之主要因素，鉍離子濃度越大其合成之粉末粒徑越小。DTA/TG 分析結果顯示，起始碳酸氧鉍粉末越小，所需熱處理之溫度越低，因此，本研究使用鉍離子與尿素之化學計量比例 (Urea/Bi3+) 為 5 時，鉍離子濃度為 0.7 M 之合成條件下，以 500°C 持溫 2 小時進行熱處理可合成出奈米級氧化鉍粉末。可見光/紫外光吸收光譜顯示，當粉末晶粒較大時，會使能隙有變小的趨勢。

　　In the first part of this study, micron-scale bismuth oxide (Bi2O3) powder have been prepared via chemical precipitation by using bismuth nitrate (Bi(NO3)3) as starting material and NaOH as the precipitating agent. The influence of bismuth concentration and molar ratio of NaOH (NaOH/Bi3+) on the formation of Bi2O3 was investigated. When NaOH/Bi3+ = 5, single phase of monoclinic Bi2O3 powder could be synthesized in room temperature. When the molar ratio of NaOH increased, the presence of Bi(OH)3 were observed. The morphology of Bi2O3 powder was needle-like. When the bismuth concentration or quality of NaOH increased, the aspect ratio of powder would decreased, and subjected to progressive increase of particle size. TEM analysis indicated that the needle-like particle is single particle and has a preferred growth direction of [0 0 1].
　　The second part, nanoscale Bi2O3 powder have been prepared via urea-hydrothermal method. The hydrothermally synthesized precursor were indexed to a phase of bismutite (Bi2O2CO3). The precursor were heat-treated to nano-scale Bi2O3 powder. The major factor controlling Bi2O2CO3 particle size was the concentration of bismuth, an increase in bismuth concentration subjected to a progressive decrease of the particle size. When the particle size of Bi2O2CO3 decreased, the temperature of synthesized decreased. Therefore, in this study, the nano-scale Bi2O3 would be obtained at bismuth concentration at 0.7 M and the molar ratio of Urea and Bi3+ (Urea/Bi3+) at 5 after calcining at 500°C for 2 hours. As the particle size of Bi2O3 increased, band gap was decreased.

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