鉻摻雜鈦酸釔應用於固態氧化物燃料電池電解質材料之研究

Abstract

在本篇論文中，利用溶膠凝膠法合成以鉻摻雜Y2¬Ti2CrxO7，並使用X光粉末繞射儀、掃描式電子顯微鏡、感應耦合電漿原子發射光譜分析儀、X光光電子能譜儀、熱程控還原反應、交流阻抗儀及四點探針法去鑑定合成之材料。在X光粉末繞射圖中發現，於0 < x ≤ 0.8，Y2Ti2-xCrxO7可成功的合成出單一純相。經由精算過的單位晶格可以發現到隨著Cr的摻雜量上升，結構單位晶格是逐漸下降的。從熱程控還原反應得知樣品在350 - 450 ºC會與氫氣反應，氫氣消耗量也是隨著Cr上升而上升。以X射線光電子能譜儀分析摻雜後Cr之價態，Cr是以+3以及+6價存在於結構中，而Cr的平均價態是隨著Cr摻雜量上升而下降。並從交流阻抗儀分析結果可以得知在最高離子導電度在x = 0.2時，於700 ºC下離子導電度為 0.01 s/cm 這是由於摻雜有一個上限，超過這個上限，缺陷會互相反應，阻礙極子移動。而在氫氣底下的離子導電度會低於在氧氣底下，代表是屬於P-type 的導電性質。最後由四點探針進行導電率的研究，整個系列化合物都有著低的電子導電度，在x=0.2時於700 ºC為0.0004，加上不錯的離子導電度，相當有潛力當作中溫型燃料電池的電解質材料。

In this study, a series of Y2Ti2-xCrxO7 were synthesized by sol-gel method and characterized by powder X-ray diffraction (PXRD), scanning electron microscope energy dispersive spectroscopy (SEM-EDS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), temperature-programmed reduction (TPR), and AC- impedance to investigate their properties for the application of intermediate temperature solid oxide fuel cell (IT-SOFC). Single-phase of Y2Ti2-xCrxO7 were observed in a range of 0 < x ≤ 0.8. The refined cell parameters decreased as the amount of doped Cr concentration increased. The TPR profiles showed that the as-prepared materials started to react with hydrogen in the temperature range of 350 - 450 ºC. The analyzed results of XPS suggested that the average oxidation state of Cr decreased with the increased Cr content. Measurements of ionic conductivities were carried out and the optimized performance was observed at x = 0.2 with 0.01 S/cm at 700 ºC due to an optimized condition of carrier concentration and carrier mobility. The ionic conductivity dropped under reducing condition, indicative of a p-type semiconductor. The as-prepared Y2Ti1.8Cr0.2O7 exhibits low electrical conductivity (0.0004 S/cm at 700 ºC) and good ionic conductivity, which is potentially suitable to be utilized as an electrolyte material for IT-SOFC.