結論與未來展望

本論文研究未摻雜及摻雜不同離子 CNO 樣品的 x 光繞射能譜、

變溫拉曼散射光譜及橢圓偏光光譜。實驗結果歸納為以下四點結論：

第一，由 x 光繞射能譜分析得知，摻雜不同離子造成晶格常數的 改變量非常微小(約只有百分之二左右)，我們發現摻雜 Rb、V 及 Ta 之樣品，其單位晶胞體積皆略為減小，而摻雜 S 離子樣品之單位晶胞 體積有變大的趨勢，這是因為摻雜離子半徑不同所致。

第二，由室溫拉曼散射光譜研究得知，摻雜陽離子取代 Nb 離子，

引起 620 cm^-1拉曼峰的改變較為明顯，分別紅移了三個波數及兩個波 數，此振動模對應鈮氧八面體之伸張振動，能夠靈敏的反應摻雜離子 的狀態。此振動模係因摻雜 V 及 Ta 離子取代 Nb 離子後，八面體中 與氧鍵結之鍵長伸長所致。

第三，我們以非簡諧振動模型擬合高溫拉曼散射光譜，拉曼峰頻 率及半高寬隨溫度上升有一斜率不連續之轉折點，我們推測此轉折點 區間範圍為其相變溫度，所有樣品之相變溫度皆較未摻雜樣品的相變 溫度還低，推測摻雜不同離子增加晶格無序度，晶格結構發生局部扭 曲，進而導致反鐵電-順電相變溫度下降。

不變，但以 V 離子及 Ta 離子取代 Nb 離子、及以 S 離子取代 O 離子 之能隙值皆明顯下降。CNO 樣品之價電帶及導電帶分別主要由 O 的

2p 及 Nb 的 4d 軌域所貢獻，因此取代 Cs 離子並未直接牽涉到 O 的 2p 及 Nb 的 4d 軌域之改變，故對能隙的影響較小，我們並進一步比

摻雜陽離子與未摻雜樣品相比，其能隙值改變趨勢與理論計算一致，

但理論計算低估了實驗上摻雜 Ta 離子及摻雜 V 離子後對能隙的改變 量；而摻雜陰離子與未摻雜樣品相比，能隙值改變趨勢與理論計算結 果亦相同。由於取代 Nb 離子之摻雜對能隙降低影響最為顯著，我們 建議透過取代 Nb 離子之 V 離子或是 Ta 離子摻雜，使 CNO 樣品成為 僅需經由太陽光照射，即可將水分解為氫氣與氧氣的高效率光觸媒材 料。

未來我們希望能對 CNO 樣品進行電性量測及同步輻射 x 光繞射 能譜分析，準確地確認反鐵電-順電相變溫度，及精確的晶格常數數 值。此外，我們也希望量測摻雜不同濃度 V 離子及 Ta 離子 CNO 樣 品之拉曼散射及橢圓偏光光譜，藉以定量指出摻雜對拉曼峰及能隙值 之影響，並期望能得出某特定比例摻雜下之 CNO 樣品，其能隙值降 低幅度最大。

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