臺灣大學: 材料科學與工程學研究所韋文誠周曈Chou, TungTungChou2013-03-222018-06-282013-03-222018-06-282011http://ntur.lib.ntu.edu.tw//handle/246246/251757螢石結構的鉺鈮氧化物共摻雜氧化鉍(縮寫為ENSB)擁有應用於中溫固態氧化物燃料電池(IT-SOFC)電解質的潛力。本研究利用膠粒製程，製作三成分混合的ENSB生胚，在870oC燒結16小時後，具有良好的密度與均勻度，並對ENSB的相穩定、導電度、長時間操作性、離子傳導係數做深入的探討。 本研究探討發鉺/鈮摻雜的比例與濃度，對於相穩定及電性的影響。利用特定鉺/鈮摻雜比例，總摻雜濃度(TDC)可以降到10 mol%來穩定得單相的δ相氧化鉍，並觀察到一個不尋常的晶格收縮行為，而當摻雜濃度低於10 mol%時，正方結構的β相會在降溫過程中生成。我們也利用TEM及EDS對晶界做化學成分的分析，發現在晶界附近並沒有明顯的偏析現象發生。 導電性方面利用兩點式直流測量，發現6.7E3.3NSB(6.7 mol% Er2O3和3.3 mol% Nb2O5共摻雜氧化鉍) 最佳的導電度在500oC、600oC與700oC分別為 0.351、0.209與0.116 Scm-1，10E5NSB則在650oC，300小時的熱處理下，展現最佳的相穩定性與穩定的導電性1.6x10-2 Scm-1。接著利用DTA、TEM、SEM及XRD及兩點式直流測量，證明電性劣化的機制不是因為氧空缺有序化，而是由γ-相生成所控制。最後，利用EMF法來測量ENSB的離子傳導係數，在600oC以上，離子傳導係數皆可達到大於0.9的水準，具有良好的離子導電性。Er- and Nb- co-doped Bi2O3 materials (abbreviated as ENSB) with fluorite structure show a great potential to be applied as the electrolyte of intermediate temperature-solid oxide fuel cell (IT-SOFC). The colloidal process was used to prepare well-mixed green bodies and sintered at 870oC for 16 hr to get homogenous and dense ENSB samples. The phase stabilization, electrical conductivity, long-term test, and ionic transference number of ENSBs were studied. This study investigated the effects of dopant ratio Er/Nb, minimal total doping concentration (TDC) on several interesting electric conductive properties. The TDC can be decreased to 10 mol% which is still able to stabilize δ-Bi2O3 in short term. However, when the concentration is lower than 10 mol%, tetragonal β-Bi2O3 appears after cooling. Additionally, an abnormal lattice contraction behavior of the δ-phase was observed in the ENSB. TEM and micro-beam EDS were carried out to analyze the composition around the grain boundaries. No significant segregations of the dopants were found around the grain boundaries. 6.7E3.3NSB (6.7 mol% Er2O3 and 3.3 mole% Nb2O5 co-doped stabilized Bi2O3) exhibited best conductivity of 0.351, 0.209, and 0.116 Scm-1 at 500oC, 600oC and 700oC, respectively, which were measured by 2-probes DC method. The 10E5NSB presents the best phase stability and stable conductivity of 1.6x10-2 Scm-1 after annealing at 650oC for 300 hr. The DTA, TEM, SEM and XRD results demonstrated the degradation of conductivity of 10E5NSB at 650oC, which was controlled by γ-phase formation, not by oxygen vacancy-ordering. The ionic transference number of ENSB measured by EMF method is greater than 0.9 at 600oC to 700oC. High transference number implies high ionic conductivity of ENSB materials.5512651 bytesapplication/pdfen-US氧化鉍固態氧化物燃料電池螢石結構導電性離子傳導係數Bi2O3SOFCconductivityfluoriteionic transference numberannealingthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/251757/1/ntu-100-R98527040-1.pdf