https://scholars.lib.ntu.edu.tw/handle/123456789/74007
標題: | 釔鈮共摻雜氧化鉍電解質之均勻性、相變化及長時間電性研究 Investigation of Homogeneity, Phase Transformation and Long-term Conductivity of Nb and Y Co-doped Bi2O3-Based Electrolyte |
作者: | 戴字庭 Dai, Zih-Ting |
關鍵字: | 氧化鉍;固態氧化物燃料電池;長時間導電性;離子傳導係數;均勻性;Bismuth oxide;SOFC;Long-term conductivity;Transference number;Homogeneity | 公開日期: | 2011 | 摘要: | 本研究合成鈮釔添加的氧化鉍電解質材料,並針對(1)提高氧化釔的分散性,(2)提升鈮及釔、鉺在樣品中的均勻性,(3)鈮:釔的最佳比例及最佳總摻雜量,(4)長時間電性的裂化特性予以分析。經過酒精改質的氧化釔粉體,不僅其分散性及均勻性都有所提升,其導電性亦有顯著的變化。在樣品21NY(5:2)中,氧化鈮及氧化釔的成分標準差分別為0.20 mol%及0.18 mol%。同時,此改質粉體方法對於鈮、鉺系統也具有同樣的效果。另外藉由粉體表面電位、紅外線光譜儀、總有機碳分析的結果,可以建立氧化釔在水溶液中的分散機制。探討摻雜比例及總摻雜量對相穩定的影響,發現最低能夠穩定單相δ氧化鉍的組成為12NY(3:1),其在650oC,初始導電性為0.07 Scm-1。在長時間相穩定測試中,樣品21NY(3:1)、15NY(3:1)及12NY(3:1)在650oC,熱處理800小時後均維持單一的δ相。而其中以15NY(3:1)有最好的導電穩定性,在經過300小時的測試後仍有初始導電性的60% (0.0196 Scm-1)。利用XRD、SEM、DTA及TEM證明本系統電解質的電性裂化機制是由於表面生成的第二相(α’)所控制。同時增加鈮在樣品中的比例,可以有效的抑制第二相的生成。藉由EMF法量測樣品15NY(3:1)的離子傳導係數 在操作溫度650oC,其離子傳導係數為0.62,顯示此成分作為固態氧化物燃料電池之電解質仍有改善的空間。 This work synthesized Nb and Y–codoped Bi2O3 materials used as the electrolyte of solid oxide fuel cells. Four objectives (1) improving dispersion of Y2O3 powder, (2) increasing homogeneity of Nb and Y content in the materials, (3) optimizing the ratio of Nb/Y and total doping concentration (TDC), (4) understanding the degradation of long-term conductivity, are investigated. Not only the dispersion and homogeneity were increased by using modified Y2O3 powder, but the conductivity of the samples was also promoted. In sample 21NY(5:2), the standard deviations of Nb and Y content are 0.20 mol% and 0.18 mol%, respectively. Moreover, the method of powder modified by ethanol was also effective on Nb, Er-codoped system. Based on the results of zeta-potential, IR spectrum, and TOC, the dispersion mechanism of Y2O3 in aqueous solution was proposed. The optimal composition in Bi2O3-Nb2O5-Y2O3 system to stabilize δ-phase at room temperature was 12NY(3:1) with 0.07 Scm-1 of short-term conductivity at 650oC. For long-term stability, 21NY(3:1), 15NY(3:1), and 12NY(3:1) showed excellent phase stability, which maintained δ-phase after annealing at 650oC for 800 h. However, 15NY(3:1) has the best long-term conductivity with 60% (0.0196 Scm-1) retention of initial value after 300 h aging. On the other hand, the conductivity decay was governed by the formation of second phase (α’) on the surface. The transference number of 15NY(3:1) was 0.62 at 650oC. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/251719 |
顯示於: | 材料科學與工程學系 |
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