Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF)屬於鈣鈦礦材料並具備良好的電子及離子導性，可應用於壓力驅動型氧傳輸膜(oxygen transport membrane, OTM)，於高溫下(>700oC)藉由氧傳輸膜兩端的氧分壓差作為驅動力從空氣中分離純氧(purity>95%)，是近年來最具前景的氧傳輸膜材料之一。同時，為了實現氧傳輸膜於空氣分離系統的應用，許多氧傳輸元件的設計與模組化方法在近年來陸續被提出，本研究的第一部分著重於Ba0.5Sr0.5Co0.8Fe0.2O3-δ管型氧傳輸元件的製備、封裝與模組化，並選用具成本優勢的注漿成型法來製備一端閉口之管型氧傳輸膜，藉由控制懸浮液的溶劑種類及分散劑、黏結劑的添加量來製備流動性質佳且高穩定性的注漿漿料，經注漿、乾燥及脫模等製程後成功製備一端閉管式之管型氧傳輸元件，元件生胚直徑8 mm、長80 mm。管型氧傳輸元件與不鏽鋼金屬底座的封裝則是以銀焊(Reactive air brazing, RAB)方法完成，經過96小時的熱穩定測試，SEM微結構分析顯示其接合界面的孔隙度並未隨持溫時間增加而產生進一步變化。本研究成功建立管型氧傳輸模組，單一模組由10支管型元件組成，模組於進氣端為空氣氣氛及溫度900oC下的產氧率為104.58 ml/min。
另一方面，許多以鹼土金屬(鈣、鍶、鋇)作為A-site離子的鈣鈦礦結構材料雖然具備良好的氧傳輸量，但近年來陸續發現這類材料在二氧化碳氣氛下晶體結構不穩定而容易析出碳酸鹽類並進一步導致氧傳輸膜的氧傳輸量降低。本研究的第二部分分別選取具有較高價數的鑭和铌當作摻雜離子，藉由改變摻雜濃度觀察鑭和铌的摻雜對於Ba0.5Sr0.5Co0.8Fe0.2O3-δ的晶體結構、導電率、氧傳輸量與對二氧化碳氣氛忍受力的影響。其中Ba0.5Sr0.5Co0.8-XFe0.2NbxO3-δ (x=0.05~0.15) 與 LayBa0.5-ySr0.5Co0.7Fe0.2Nb0.1O3-δ (y=0.05~0.15)在950oC下鍛燒8小時後都能形成立方相的鈣鈦礦結構。
Ba0.5Sr0.5Co0.8Fe0.2O3-δ於800oC及空氣氣氛下的導電率為31.7 S/cm，而隨著鈮摻雜濃度的增加(Ba0.5Sr0.5Co0.8-XFe0.2NbxO3-δ, x=0.05~0.15)，導電率則呈現下降的趨勢，而隨著鑭的進一步摻雜 (LayBa0.5-ySr0.5Co0.7Fe0.2Nb0.1O3-δ, y=0.05~0.15)，導電率則隨著鑭的摻雜濃度增加而提升，當A-site的鑭摻雜量為15%時，其在空氣氣氛及溫度800oC的導電率為108.15 S/cm。在材料於二氧化碳氣氛下的性質表現方面，Ba0.5Sr0.5Co0.8Fe0.2O3-δ於含有10%二氧化碳的空氣氣氛下晶體結構不穩定，易分解為碳酸鋇或碳酸鍶且氧傳輸量迅速衰退，於800oC及10%二氧化碳氣氛下測試70小時後，其氧傳輸量衰退了89.4%，另一方面，雖然在鑭與鈮摻雜後的氧傳輸膜仍然可以透過XRD分析觀察到碳酸鹽類的析出，但其在二氧化碳氣氛下的氧傳輸量衰退率有明顯改善，於800oC及10%二氧化碳氣氛下測試70小時後，Ba0.5Sr0.5Co0.8-XFe0.2NbxO3-δ (x=0.05, 0.10及0.15)與 LayBa0.5-ySr0.5Co0.7Fe0.2Nb0.1O3-δ (y=0.05, 0.10)的氧傳輸量衰退率分別為47.4%、47.3%、33.0%、30.2%與18.8%。

Ba0.5Sr0.5Co0.8Fe0.2O3-δ is a MIEC (mixed ionic-electronic conductor) material with a perovskite structure. It is one of the most promising oxygen transport membrane (OTM) materials due to its combined electronic and oxygen ion conduction behavior.
To fulfill the oxygen mass production from oxygen transport membranes, several concepts and designs of OTM module have been proposed in the last decades. In addition, several perovskite oxide material containing large alkaline earth metal element as their A-site ions have been reported to be sensitive to CO2, which will limit their application in oxy-fuel combustion. In recent years, some research suggested that perovskite material with dopants may enhance the structural stability and suppress the CO2 reaction.
In the first part of this study, in order to realize the integration of oxygen transport membranes for oxygen generation, we focused on the fabrication, sealing and modulization of Ba0.5Sr0.5Co0.8Fe0.2O3-δ tubular oxygen transport membranes. The fabrication of one-end-closed tubular Ba0.5Sr0.5Co0.8Fe0.2O3-δ membrane was achieved by the non-aqueous slip casting. The influence of organic solvent, dispersant and binder concentration is also discussed. Tubular green body with 8 mm diameter and 80 mm length were successfully sintered and then sealed with stainless steel by reactive air brazing method (RAB). The SEM images showed that there was no increasing of porosity at the membrane/brazing interface with aging time up to 96 hours. A tubular oxygen transport module within 10 oxygen transport membranes inside was successfully accomplished. The oxygen permeation rate of this module is 104.58 ml/min at 900oC with air as feed gas.
In addtion, to improve the CO2-tolerance of Ba0.5Sr0.5Co0.8Fe0.2O3-δ membrane, the second part of this study selected the niobium ion to substitute the B-site cobalt ion due to their stable high valence state and lanthanum ion to substitute the A-site barium ion due to their lower ionic radius. The doping concentration of both lanthanum and niobium ions are varied from 5~15% at A-site and B-site, respectively. The effect of doping concentration on their crystal structure, electronic conductivity, oxygen permeation flux and CO2 tolerance ability were investigated. All the compositions denoted as Ba0.5Sr0.5Co0.8-XFe0.2NbxO3-δ (x=0.05~0.15) and LayBa0.5-ySr0.5Co0.7Fe0.2Nb0.1O3-δ (y=0.05~0.15) were synthesized and confirmed by XRD as cubic perovskite phase. Both electrical conductivity and oxygen transport flux of Ba0.5Sr0.5Co0.8-XFe0.2NbxO3-δ tends to decrease with increasing niobium concentration, which may be explained by the effect of charge compensation. On the other hand, although the doping of lanthanum will decrease the oxygen permeation flux, the electrica conductivity increased from 26.42 S/cm to 108.15 S/cm by substitution of 0~15% lanthanum for A-site barium ion. During exposure to 10% CO2-containing atmosphere for 60 hours, un-doped Ba0.5Sr0.5Co0.8Fe0.2O3-δ decomposed into barium and strontium carbonate and its oxygen permeation flux is lowered by 89.4 % after 70 hours. On the other hand, although some carbonates still formed in the Ba0.5Sr0.5Co0.8-XFe0.2NbxO3-δ and LayBa0.5-ySr0.5Co0.7Fe0.2Nb0.1O3-δ compositions, the deterioration of oxygen permeation flux was suppressed, which is lowered by 47.4, 47.3, 33.0, 30.2 and 18.8%, respectively.

1. Stadler, H., Beggel, F., Habermehl, M., Persigehl, B., Kneer, R., Modigell, M., & Jeschke, P. "Oxyfuel coal combustion by efficient integration of oxygen transport membranes." International Journal of Greenhouse Gas Control 5.1 (2011): 7-15
2. Buhre, B. J., Elliott, L. K., Sheng, C. D., Gupta, R. P., & Wall, T. F. "Oxy-fuel combustion technology for coal-fired power generation." Progress in energy and combustion science 31.4 (2005): 283-307.
3. Baumann, S., Serra, J. M., Lobera, M. P., Escolástico, S., Schulze-Küppers, F., & Meulenberg, W. A. "Ultrahigh oxygen permeation flux through supported Ba0.5Sr0.5Co0.8Fe0.2O3- δ membranes." Journal of Membrane Science 377.1 (2011): 198-205.
4. M.Czypereka., P.Zappa., H.J.M.Bouwmeesterb., M.Modigellc., K.Ebertd., I.Voigte., W.A.Meulenberga., L.Singheisera., D.Stövera. "Gas separation membranes for zero-emission fossil power plants: MEM-BRAIN." Journal of membrane science 359.1 (2010): 149-159.
5. Sunarso, J., Baumann, S., Serra, J. M., Meulenberg, W. A., Liu, S., Lin, Y. S., & Da Costa, J. D. "Mixed ionic–electronic conducting (MIEC) ceramic-based membranes for oxygen separation." Journal of Membrane Science 320.1 (2008): 13-41. 6. Peng, R., et al., "Characteristics of La0.85Sr0.15MnO3–δ Powders Synthesized by a Glycine-Nitrate Process. " Fuel Cells, 2006. 6(6): p. 455-459.
6. Arnold, Mirko, Haihui Wang, and Armin Feldhoff. "Influence of CO2 on the oxygen permeation performance and the microstructure of perovskite-type (Ba 0.5 Sr 0.5)(Co 0.8 Fe 0.2)O3− δ membranes." Journal of Membrane Science293.1 (2007): 44-52.
7. A.Y. Yan, L. Bin, Y.L. Dong, Z.J. Tian, D.Z.Wang, M.J. Cheng, Appl. "Effect of microstructure and catalyst coating on the oxygen permeability of a novel CO2-resistant composite membrane. " Catal. B Environ. 80 (2008) 24–31.
8. Ito, W., T. Nagai, and T. Sakon. "Oxygen separation from compressed air using a mixed conducting perovskite-type oxide membrane." Solid State Ionics 178.11 (2007): 809-816.
9. Nagai, T., W. Ito, and T. Sakon. "Relationship between cation substitution and stability of perovskite structure in SrCoO3–δ-based mixed conductors." Solid State Ionics 177.39 (2007): 3433-3444.
10. Wang, F., Nakamura, T., Yashiro, K., Mizusaki, J., & Amezawa, K. "Effect of Nb doping on the chemical stability of BSCF-based solid solutions." Solid State Ionics 262 (2014): 719-723.
11. Pérez‐Ramírez, Javier, and Bent Vigeland. "Perovskite membranes in ammonia oxidation: towards process intensification in nitric acid manufacture." Angewandte Chemie International Edition 44.7 (2005): 1112-1115.
12. Zeng, Y., and Y. S. Lin. "Oxygen permeation and oxidative coupling of methane in yttria doped bismuth oxide membrane reactor." Journal of Catalysis 193.1 (2000): 58-64.
13. Capoen, Edouard, et al. "Oxygen permeation in bismuth-based materials. Part II: Characterisation of oxygen transfer in bismuth erbium oxide and bismuth calcium oxide ceramic." Solid State Ionics 177.5 (2006): 489-492.
14. Capoen, E., Nowogrocki, G., Chater, R. J., Skinner, S. J., Kilner, J. A., Malys, M., J.C. Boivin, G. Mairesse, R.N. Vannier "Oxygen permeation in bismuth-based materials. Part I: Sintering and oxygen permeation fluxes." Solid State Ionics 177.5 (2006): 483-488.
15. Thorogood, R. M., Srinivasan, R., Yee, T. F., & Drake, M. P. "Composite mixed conductor membranes for producing oxygen." U.S. Patent No. 5,240,480. 31 Aug. 1993.
16. Donkelaar, Sebastiaan Frederik Pouwel. Development of stable oxygen transport membranes. Universiteit Twente, 2015.
17. Fernández-Garcıa, M., Martınez-Arias, A., Guerrero-Ruiz, A., Conesa, J. C., & Soria, J. "Ce–Zr–Ca ternary mixed oxides: structural characteristics and oxygen handling properties." Journal of Catalysis 211.2 (2002): 326-334.
18. Garcia-Fayos, J., Vert, V. B., Balaguer, M., Solís, C., Gaudillere, C., & Serra, J. M. "Oxygen transport membranes in a biomass/coal combined strategy for reducing CO2 emissions: Permeation study of selected membranes under different CO2-rich atmospheres." Catalysis Today 257 (2015): 221-228..
19. Engels, S., Beggel, F., Modigell, M., & Stadler, H. "Simulation of a membrane unit for oxyfuel power plants under consideration of realistic BSCF membrane properties." Journal of Membrane Science 359.1 (2010): 93-101.
20. Kotowicz, Janusz, and Adrian Balicki. "Enhancing the overall efficiency of a lignite-fired oxyfuel power plant with CFB boiler and membrane-based air separation unit." Energy Conversion and Management 80 (2014): 20-31.
21. Schiestel, T., Kilgus, M., Peter, S., Caspary, K. J., Wang, H., & Caro, J. "Hollow fibre perovskite membranes for oxygen separation." Journal of Membrane Science 258.1 (2005): 1-4.
22. Vente, Jaap F., Wim G. Haije, and Zbigniew S. Rak. "Performance of functional perovskite membranes for oxygen production." Journal of Membrane Science 276.1 (2006): 178-184.
23. Armstrong, P. A., Bennett, D. L., Foster, E. P., & Stein, V. E. "Ceramic membrane development for oxygen supply to gasification applications." Proceedings of the Gasification Technologies Conference, San Francisco, CA, USA. 2002.
24. Zhang, Y., Zeng, F., Yu, C., Wu, C., Ding, W., & Lu, X. "Fabrication and characterization of dense BaCo 0.7Fe0.2Nb0.1O3−δ tubular membrane by slip casting. " Ceramics International 41.1 (2015): 1401-1411.
25. Vente, J. F., Haije, W. G., IJpelaan, R., & Rusting, F. T. "On the full-scale module design of an air separation unit using mixed ionic electronic conducting membranes." Journal of membrane science 278.1 (2006): 66-71.
26. Pfaff, Ewald M., Anke Kaletsch, and Christoph Broeckmann. "Design of a mixed ionic/electronic conducting oxygen transport membrane pilot module." Chemical Engineering & Technology 35.3 (2012): 455-463.
27. Guo, D., Cai, K., Huang, Y., Li, L., & Gui, Z. "Water based gelcasting of lead zirconate titanate." Materials research bulletin 38.5 (2003): 807-816.
28. Choi, M. B., Lim, D. K., Jeon, S. Y., Kim, H. S., & Song, S. J. "Oxygen permeation properties of BSCF5582 tubular membrane fabricated by the slip casting method." Ceramics International 38.3 (2012): 1867-1872.
29. Tiller, F. M., & TSAI, C. D. "Theory of filtration of ceramics: I, slip casting." Journal of the American Ceramic Society 69.12 (1986): 882-887.
30. Bergström, Lennart. "Rheological properties of concentrated, nonaqueous silicon nitride suspensions." Journal of the American Ceramic Society 79.12 (1996): 3033-3040.
31. Zhang, Jingxian, Dongliang Jiang, and Qingling Lin. "Poly (Vinyl Pyrrolidone), a Dispersant for Non‐Aqueous Processing of Silicon Carbide." Journal of the American Ceramic Society 88.4 (2005): 1054-1056.
32. Guo, D., Cai, K., Huang, Y., Li, L., & Gui, Z. "Water based gelcasting of lead zirconate titanate." Materials research bulletin 38.5 (2003): 807-816.
33. Boschini, F., Rulmont, A., Cloots, R., & Moreno, R. "Rheological behaviour of BaZrO3 suspensions in non-aqueous media." Ceramics International 35.3 (2009): 1007-1013.
34. Zhang, Yongheng, and Jon Binner. "Enhanced casting rate by dynamic heating during slip casting." Journal of the European Ceramic Society 22.1 (2002): 135-142.
35. Borhan, A. I., Gromada, M., Nedelcu, G. G., & Leontie, L. "Influence of additives (CoO, CaO, B2O3) on thermal and dielectric properties of BaO-Al2O3-SiO2 glass-ceramic sealant for OTM applications." arXiv preprint arXiv:1507.03390 (2015).
36. Kerstan, M., Thieme, C., Grosch, M., Müller, M., & Rüssel, C. "BaZn2Si2O7 and the solid solution series BaZn 2− xCoxSi2O7 (0< x≤ 2) as high temperature seals for solid oxide fuel cells studied by high-temperature X-ray diffraction and dilatometry." Journal of Solid State Chemistry 207 (2013): 55-60.
37. Geiger, P. T., Clemens, O., Khansur, N. H., Hinterstein, M., Sahini, M. G., Grande, T., Patrick TUng, John E. Daniels & Webber, K. G. "Nonlinear mechanical behaviour of Ba0.5Sr0.5Co0.8Fe0.2O3- δ and in situ stress dependent synchrotron X-ray diffraction study." Solid State Ionics 300 (2017): 106-113.
38. Weil, K. Scott, Jin Yong Kim, and John S. Hardy. "Reactive air brazing: a novel method of sealing SOFCs and other solid-state electrochemical devices." Electrochemical and solid-state letters 8.2 (2005): A133-A136.
39. Kaletsch, Anke, Ewald M. Pfaff, and Christoph Broeckmann. "Effect of Aging on Microstructure and Mechanical Strength of Reactive Air Brazed BSCF/AISI 314‐Joints." Advanced Engineering Materials 16.12 (2014): 1430-1436.
40. Joshi, V. V., Meier, A., Darsell, J., Weil, K. S., & Bowden, M. "Trends in wetting behavior for Ag-CuO braze alloys on BaSrCoFeO at elevated temperatures in air." Journal of materials science 48.20 (2013).
41. Zeng, P., Chen, Z., Zhou, W., Gu, H., Shao, Z., & Liu, S "Re-evaluation of Ba0.5Sr0.5Co0.8Fe0.2O3- δ perovskite as oxygen semi-permeable membrane." Journal of Membrane Science 291.1 (2007): 148-156.
42. Shao, Z., Yang, W., Cong, Y., Dong, H., Tong, J., & Xiong, G. "Investigation of the permeation behavior and stability of a Ba0.5Sr0.5Co0.8Fe0.2O3- δ oxygen membrane." Journal of Membrane Science 172.1 (2000): 177-188.
43. Arnold, Mirko, Haihui Wang, and Armin Feldhoff. "Influence of CO2 on the oxygen permeation performance and the microstructure of perovskite-type (Ba0.5Sr0.5)(Co0.8Fe0.2)O3− δ membranes." Journal of Membrane Science 293.1 (2007): 44-52.
44. Yan, A., Liu, B., Dong, Y., Tian, Z., Wang, D., & Cheng, M. "A temperature programmed desorption investigation on the interaction of Ba0.5Sr0.5Co0.8Fe0.2O3- δ perovskite oxides with CO2 in the absence and presence of H2O and O2." Applied Catalysis B: Environmental 80.1 (2008): 24-31.
45. Cho, Y. Z., Yang, H. C., Eun, H. C., Kim, E. H., & Kim, I. T. "Carbonate reaction of alkaline-earth element by carbonate agent injection method." Journal of nuclear science and technology 45.5 (2008): 459-463.
46. Yan, Aiyu, et al. "Investigation of a Ba0.5Sr0.5Co0.8Fe0.2O3- δ based cathode SOFC: II. The effect of CO2 on the chemical stability." Applied Catalysis B: Environmental 76.3 (2007): 320-327.
47. Yan, A., Maragou, V., Arico, A., Cheng, M., & Tsiakaras, P. "Behavior of Ba(Co, Fe, Nb)O3-δ perovskite in CO2-containing atmospheres: degradation mechanism and materials design." Chemistry of Materials 22.23 (2010): 6246-6253.
48. Fang, W., Steinbach, F., Chen, C., & Feldhoff, A. "An Approach To Enhance the CO2 Tolerance of Fluorite–Perovskite Dual-Phase Oxygen-Transporting Membrane." Chemistry of Materials 27.22 (2015): 7820-7826.
49. Jung, Jae-Il, Scott T. Misture, and Doreen D. Edwards. "Oxygen stoichiometry, electrical conductivity, and thermopower measurements of BSCF (Ba0.5Sr0.5CoxFe1-xO3- δ, 0≤ x≤ 0.8) in air." Solid State Ionics 181.27 (2010): 1287-1293.
50. Tai, L. W., Nasrallah, M. M., Anderson, H. U., Sparlin, D. M., & Sehlin, S. R. "Structure and electrical properties of La1− xSrxCo1-yFeyO3. Part 1. The system La0. 8Sr0.2Co1−yFeyO3." Solid State Ionics 76.3-4 (1995): 259-271.
51. Tai, L. W., Nasrallah, M. M., Anderson, H. U., Sparlin, D. M., & Sehlin, S. "Structure and electrical properties of La1− xSrxCo1− yFeyO3. Part 2. The system La1− xSrxCo0. 2Fe0. 8O3." Solid State Ionics 76.3-4 (1995): 273-283.
52. Jeong, N. C., Lee, J. S., Tae, E. L., Lee, Y. J., & Yoon, K. B. "Acidity scale for metal oxides and Sanderson's electronegativities of lanthanide elements." Angewandte Chemie International Edition 47.52 (2008): 10128-10132.
53. Wei, Y., Ravkina, O., Klande, T., Wang, H., & Feldhoff, A. "Effect of CO2 and SO2 on oxygen permeation and microstructure of (Pr0.9La0.1)2(Ni0.74Cu0.21Ga0.05)O4+ δ membranes." Journal of Membrane Science 429 (2013): 147-154.
54. Barin, Ihsan, and Gregor Platzki. Thermochemical data of pure substances. Vol. 304. No. 334. Weinheim: VCH, 1989.
55. Efimov, K., Klande, T., Juditzki, N., & Feldhoff, A. "Ca-containing CO 2-tolerant perovskite materials for oxygen separation." Journal of membrane science 389 (2012): 205-215.