固態氧化物燃料電池電解質材料，主要以螢石結構材料之導氧材料為主。氧化鋯基與氧化鈰基電解質為常被使用之電解質之ㄧ，故本文以此兩種材料系統作為我們研究探討方向。
首先對氧化鋯基材料研究以不同離子半徑之三價陽離子(RE=Yb3+, Er3+, Y3+, Dy3+, Y3+Nd3+, Sm3+, Nd3+)與五價陽離子(Nb5+)共摻雜於氧化鋯(3Y)中，探討對氧化鋯相變機制、機械及導電的性質之影響。藉XRD分析添加物添加對氧化鋯(3Y)之晶格參數與正方性(c/a)變化，了解相變溫度變化，且由SEM觀察顯微結構之晶粒大小，以及利用交流阻抗分析儀溫度在300℃~800℃區間量測三價與五價陽離子共摻雜於氧化鋯電解質中對電性之影響。研究結果顯示平均離子半徑越大的陽離子氧化物添加於氧化鋯(3Y)中，其t相的c/a值越大，且造成t-to-m相變溫度的提升。而當平均陽離子半徑超過臨界尺寸 =0.855Å時，便很容易有t-to-m發生，導致其機械性質降低；實驗顯示添加RENbO4會使氧化鋯(3Y)韌性的提升，優於本身氧化鋯(3Y-TZP)的機械性質，由於可以承受熱反覆的熱疲勞應力，故可以應用於固態氧化物燃料電池(SOFC)電解質間歇高溫操作上，以延長電池的壽命；但在電性的分析中發現，添加RENbO4於氧化鋯(3Y)中會因Nb的添加使導電性下降，主要原因由於添加之Nb其lattice binding energy(330 eV)過大且造成部分氧空缺消耗，使得導電性下降。
利用氧化鋯基材料系統的導電性的概念來對氧化鈰基材料作研究，藉由摻雜二價離子中lattice binding energy 較小的鍶離子與三價釤離子共摻雜於氧化鈰中，藉由硬球殼模型計算發現三價釤與二價鍶共摻雜於氧化鈰中所形成的氧空缺半徑各不相同，分別為1.20Å與0.935Å，且氧空缺半徑不受摻雜濃度所影響。而針對單一摻雜不同三價陽離子半徑來作討論，發現氧空缺半徑大小會受摻雜元素而改變，且在導電性與氧空缺半徑大小作比較，氧空缺半徑愈大，使結構中有更寬的通道，而導電性有隨之增加趨勢。Ce0.8-xSm0.2SrxO1.9-x導電率隨溫度增加而增加，且摻雜量x =0.02時擁有最佳的導電率，此時在電解質中氧空缺含量為理想值，而在800℃導電率為0.0610(S•cm-1)高於SDC(Ce0.8Sm0.2O1.9)之導電率0.0371(S•cm-1)一倍；尤其在低溫範圍時Ce0.78Sm0.2Sr0.02O1.88導電性更高於SDC，可知考慮鍵結能與離子大小及適當共摻雜氧空缺產生元素能有效提升氧化鈰導電之特性。

Fluorite structure based ionic conductors are the major electrolyte materials in Solid Oxide Fuel Cells (SOFC). In this thesis, ZrO2-based and CeO2-based electrolytes are the research topics, and we shall build a material design criterion for SOFC electrolytes in this research.
Firstly, we co-dope trivalent ions (RE) with different ionic radius (RE=Yb3+, Er3+, Y3+, Dy3+, Nd3+, Sm3+) and pentavalent ions (Nb5+) into 3Y-ZrO2, and investigate the relations among phase transformation mechanism, mechanical property and conductivity. We study variation of structural and transformation characteristics by analyzing the lattice parameters and tetragonality (c/a) of specimens using X-ray diffraction, evaluate microstructural evolution by SEM observation, and measure the electrical properties of specimens with trivalent and pentavalent ions co-doping into ZrO2(3Y) by an AC impedance analyzer. Experimental results show that the c/a of t-phase of doped ZrO2(3Y) becomes larger resulting in increase of the t-to-m transformation temperature when the oxides with larger average-ion radius are added into ZrO2(3Y). Furthermore, when the average-cation radius exceeds the critical value =0.855Å, t-to-m transformation leads to degradation the decrease of mechanical property of materials. Experimental results show that adding RENbO4 into 3Y-ZrO2 enhances specimen toughness, which is superior to that of 3Y-ZrO2. Being able to sustain the thermal-fatigue stress during thermal cycling, it can be used as electrolytes of SOFC during high temperature operation and prolong the life of the cell. However, results from impedance analysis show that conductivity of RENbO4-doped 3Y-ZrO2 decreases due to too large lattice binding energy of Nb2O5 and oxygen vacancy depletion induced by Nb5+ doping.
We take the concepts of doping-conductivity relationship built in ZrO2-based material system to design CeO2-base material system. By co-doping divalent ion Sr2+ and trivalent ion Sm3+ ,whose lattice bind energy are both comparativively small into CeO2 ,we found that the radius of oxygen vacancy formed by divalent and trivalent-doped specimens is different from the calculation from the Hard-Sphere model. The former is 1.2Å and the later is 0.935Å, respectively. In addition, radius of the oxygen vacancy is independent of dopant concentration. When comparing different radius of trivalent ions, we find out that different dopants generate oxygen vacancies with different radius. Larger radius of the oxygen vacancy produces wider conducting channels in the structure, and therefore conductivity increases in the specimen. The conductivity of Ce0.8-xSm0.2SrxO1.9-x becomes higher as temperature increases, and the specimen with concentration x=0.02 possesses the highest conductivity, which corresponding to the ideal concentration of oxygen vacancy in the electrolyte. The conductivity of the specimen at 800℃(0.0610 S cm-1) is twice higher than that of SDC (Ce0.8Sm0.2O1.9 ,σ=0.0371 S cm-1), and the difference is even larger at low temperature region. We conclude that co-doping with appropriate divalent and trivalent dopant concentration effectively promote the conductivity of the specimens.

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