鐠摻雜之氧化鈰電解質於中溫固態氧化物燃料電池之研究

本文成功地利用Pechini method製備出，以二氧化鈰為主體摻雜鐠之中溫固態氧化物燃料電池(intermediate temperature solid oxide fuel cell, 縮寫為IT-SOFC)的電解質材料。研究材料包括鐠單一摻雜之Ce1-xPrxO2-δ，x = 0.05-0.35和鐠與鹼土金屬共摻雜之Ce0.7Pr0.3-yMyO2-δ，M = Mg或Ca，樣品經1500℃高溫燒結後，以X光粉末繞射儀鑑定出皆為單一物相之立方瑩石結構。以Pr LⅢ-edge之X光近邊緣吸收光譜(X-ray absorption near-edge spectroscopy, 縮寫為XANES)的測量來鑑定樣品中Ce與Pr之氧化態。藉由與Pr2O3、Pr6O11和CeO2為標準品之XANES圖譜的比對，發現所有經1500℃高溫燒結過後鐠摻雜樣品之XANES圖譜相似於Pr6O11之XANES，因此樣品中Pr應是以混價(3+、4+)之氧化態存在。進一步研究發現樣品於700℃煅燒的反應過程中就有部分Pr3+會氧化成Pr4+。因此，樣品中氧空缺濃度應該低於實際鐠摻雜量所應產生之氧空缺濃度。所製備樣品的離子導電度以交流阻抗儀於400-700℃空氣下作量測。CPO體系中，樣品30CPO於700℃具有最佳氧離子導電度0.0668 Scm-1，此數值高於目前被報導於700℃下具有最佳氧離子導電度之Ce1-xGdxO2-δ (0.0316 scm-1)與Ce1-xSmxO2-δ(0.041 Scm-1)電解質材料。為了達到降低材料成本，本文也嘗試引入鹼土金屬，製備雙摻雜的CPO材料，並且探討鹼土金屬共摻雜CPO對於導電度與氧化態的影響。結果顯示，共摻雜鹼土金屬並不影響CPO之物相結構，以及Ce與Pr於樣品中之氧化態形式。導電度的影響，鎂離子共摻雜具有正面的提升效果，反之鈣離子的共摻雜反而降低了原先CPO之導電度。其中，以成分組成為Ce0.7Pr0.28Mg0.02O2-δ是所有樣品中具有最佳導電度的材料。

關鍵字

固態氧化物燃料電池；氧化鈰電解質；氧離子導體

並列摘要

Pr-doped ceria-based electrolyte for intermediate temperature solid oxide fuel cell (IT-SOFC) was successfully synthesized by Pechini process (citric acid process). All the Pr-doped ceria (CPO) of the formula Ce1-xPrxO2-δ where x = 0.05-0.35 and those co-doped with alkaline earth of the formula Ce0.7Pr0.3-yMyO2-δ, 0.01 ≦ y ≦0.05 were ceria based solid solutions of fluorite type structures, characterized by X-ray powder diffraction. A portion of Pr3+ ions doped in ceria was oxidized to Pr4+ during the calcination process at 700℃ in air. Compared with the Pr LⅢ-edge X-ray absorption near-edge spectroscopy (XANES) profiles of Pr2O3 and Pr6O11, all the XANES profiles of the Pr-doped ceria materials after calcination at 1500℃ in air were similar to that of Pr6O11. As a result, lower number of oxygen vacancies was created in the samples than that expected from the original doping ratios. The ionic conductivities of the Pr-doped ceria-based materials were measured at 400-700℃ in air by using AC impedance spectroscopy. In the CPO system, Ce0.7Pr0.3O2-δ (30CPO) gave the highest conductivity of 0.0668 Scm-1, which was higher than 0.0316 Scm-1 for Ce0.8Gd0.2O2-δ (CGO) and 0.041 Scm-1 for Ce1-xSmxO2-δ (CSO), and the latter two were reported to give the highest conductivities among ceria-based materials applied in IT-SOFC. The effect of co-doping of alkaline earth in CPMO system on ionic conductivity was also investigated. Compared with CPO, it was found that Mg2+-dopant had positive improvement in conductivity, but the Ca2+-dopant did not. The material doped with small amount of Mg2+, Ce0.7Pr0.28Mg0.02O2-δ was found to retain the unit cell dimension as that of 30CPO and gave the highest conductivity.

並列關鍵字

SOFC ； doped ceria ； oxygen ion conductor

參考文獻

3. M. L. Liu, Solid State Ionics, 144, 249, 2001

4. A. Atkinson, V. V. Kharton et al., Solid State Ionics, 174, 135, 2004

5. S.P.S. Badwal, Solid State Ionics, 52, 23, 1992

6. S.P.S. Badwal, F. T. Ciacchi, D. Milosevic, Solid State Ionics, 136-137, 91, 2000

7. H. Ohbayashi, T. Kudo, T. Gejo, Jpn. J. Appl. Phy., 13, 1, 1974

國際替代計量

鐠摻雜之氧化鈰電解質於中溫固態氧化物燃料電池之研究

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