本實驗主要在探討ZrO2電解質共摻雜不同離子半徑之二價陽離子(Sr2+，Ca2+，Mg2+)與三價陽離子(Y3+)，於1500℃/3hrs燒結，並利用XRD、SEM、AC impedance analyzer、Raman analyzer和TEM對電解質導電性質進行研究。
為了解ZrO2離子導電率提升的機制，本實驗先以8mol%Y2O3-92mol%ZrO2(8YSZ)和 12mol%CaO -88mol% ZrO2 (12CSZ)混合作為研究的系統，實驗結果顯示(12CSZ)1-x-(8YSZ)x之離子導電率並沒有高於8YSZ。(12CSZ)1-x-(8YSZ)x經由XRD分析皆為立方(cubic)相，但(12CSZ)0.5-(8YSZ)0.5經由拉曼光譜分析，在480 cm-1產生了額外的峰(extra peak)。為了明確定義此特殊的峰，利用穿透式電子顯微鏡進行研究，發現t’ 相和 m’相，而且(12CSZ)1-x-(8YSZ)x系統中太多的氧空缺將造成缺陷叢聚之現象。此可能為(12CSZ)1-x-(8YSZ)x系統離子導電率無法提升的原因。
為了提升ZrO2離子導電率，本實驗控制摻雜的量，也就是Y2O3-ZrO2相圖中，接近t-to-c轉變之位置(8 mole%)，去抑制氧空缺叢聚(oxygen vancancy cluster)之現象。所以共摻雜系統之陽離子固定8 mole%，且氧空缺濃度固定8 mole%附近。故設計Zr0.92Y0.16-XMXO2.08-0.5X，(M=Sr2+，Ca2+，Mg2+)，X=0，0.005，0.01，0.015，0.02，之成份。研究結果顯示Zr0.92Y0.16-XMXO2.08-0.5X之試片由XRD分析，皆為cubic相。而800℃時Zr0.92Y0.16-XMXO2.08-0.5X，M=Sr2+，Ca2+，Mg2+，離子導電率之最佳值，X之添加量皆為0.005 mole。而Zr0.92Y0.16-XMXO2.08-0.5X之離子導電率隨添加之二價陽離子半徑增加而減少，即σMgYZ > σCaYZ >σSrYZ。而800℃之Zr0.920Y0.155 Mg0.005O2.08-0.5X之導電率為0.022 (S•cm-1)高於(ZrO2)0.92-(Y2O3)0.08之導電率0.015 (S•cm-1)。而ZrO2-Y2O3電解質摻雜二價陽離子，添加量不能大於0.01 mole，不然會發生氧空缺序化之現象，而造成導電率下降。
由硬球殼模型計算氧空缺半徑，Zr0.92Y0.16-XMgXO2.08-0.5X，Zr0.92Y0.16-XCaXO2.08-0.5X 和Zr0.92Y0.16-XSrXO2.08-0.5X系統的氧空缺半徑為1.7508 Å，0.8652 Å和0.3421 Å，離子導電率隨著氧空缺半徑增加而增加。因為離子導電率σMgYSZ>σCaYSZ>σSrYSZ 和氧空缺半徑
的趨勢是相同的。意即利用硬球殼模型和晶格常數，可計算摻雜不同陽離子產生之氧空缺半徑，進而預估電解質材料的導電行為。
由微觀影像發現Zr0.92Y0.16-XMXO2.08-0.5X系統隨者M2+之添加，晶粒大小有增加的趨勢，但當Ca2+的添加量超過0.015mole和SrO的添加量超過0.01mole時，會在晶界發現一些生成物，是因為Ca2+和Sr2+之離子半徑皆比Zr4+大很多，且CaO-ZrO2和SrO-ZrO2並不容易形成固溶，所以CaO和SrO容易偏析於晶界並且抑制晶粒成長。
由本實驗可知控制共摻雜離子半徑接近Zr4+和晶格束縛能(lattice binding energy)較小之氧化物和摻雜的量在8 mol%附近，可提升釔安定氧化鋯電解質之離子導電性。Zr0.920Y0.155M0.005O2.08-0.5X系統，擁有突出的離子導電性，且接近Ce0.8Sm0.2O1.9 ( 0.037 S•cm-1)。
Zr0.920Y0.155M0.005O2.08-0.5X適用於SDC電解質三明治結構之抗還原層，進而降低SOFC的操作溫度，使SOFC能在中溫下長時間運作。

Co-doping effect of various ionic radii of divalent (Sr2+, Ca2+, Mg2+) and trivalent (Y3+) cations on ionic conductivity of zirconia was investigated using x-ray diffractiometry, scanning electron microscopy, transmission electron microscopy, raman spectroscopy and ac impedance analysis in this work.
For understanding the principles of enhancing the ionic conductivity of zirconia, (8YSZ)X-(12CSZ)1-X was investigated in the first topic. Experimental results show the ionic conductivity of (8YSZ)X-(12CSZ)1-X decreases with an increase of 12CSZ content. The (8YSZ)X-(12CSZ)1-X are all cubic phase calculated from x-ray diffraction patterns, but a 480 cm-1 extra peak was found from raman scattering patterns in (8YSZ)0.5-(12CSZ)0.5. It seems that another unusual phase was formed; for this reason, the microstructral feature of (8YSZ)0.5-(12CSZ)0.5 was carried out using transmission electron microscopy. The t’ phase and a peculiar monoclinic phase (m’) was observed, and the defect association or lattice distortion would be produced in (8YSZ)X-(12CSZ)1-X due to too many oxygen vacancies, which is the possible reason that the ionic conductivity (8YSZ)X-(12CSZ)1-X decreases with an increase of 12CSZ content.
Y2O3 doping concentration in zirconia of 8mol% exhibits highest ionic conductivity, and the ionic conductivity of Y2O3 doped zirconia decreased when the composition of Y2O3 higher than 8 mol% because of the oxygen vacancy clustering. In order to decrease and restrain the average binding energy and oxygen vacancy clustering in zirconia respectively for enhancing ionic conductivity, the divalent cations (Sr2+, Ca2+, Mg2+) and trivalent (Y3+) cations doped zirconia which possess the lowest lattice binding energy and the radius of doped cations close to Zr4+ was devised. Besides, the amount of doped cations of co-doping system must be fixed at 8 mol%, and the amount of oxygen vacancy was controlled around 8-9 mol% in YSZ matrix. The results demonstrate that the specimens of Zr0.92Y0.16-XMXO2.08-0.5X are of cubic structure calculated from x-ray diffraction patterns. It is found the best conductivity of Zr0.920Y0.155Mg0.005O2.08-0.5X (0.022 S•cm-1), Zr0.920Y0.155Ca0.005O2.08-0.5X (0.020 S•cm-1) and Zr0.920Y0.155Sr0.005O2.08-0.5X (0.016 S•cm-1) are higher than that of (ZrO2)0.92-(Y2O3)0.08 (0.015 S•cm-1) at 800℃. The ionic conductivity of Zr0.920Y0.155M0.005O2.08-0.5X decreases with an increase of divalent ion radius. The ordering structure of oxygen vacancies occurred in the content of divalent oxides doped with ZrO2-Y2O3 higher than 0.01. The Zr0.920Y0.155Mg0.005O2.08-0.5X co-doped system contributes a maximum content of non-interfering oxygen vacancies, the average radii of co-doping divalent cations is close to that of Zr4+ and average binding energy must be as small as possible. Following these principles helps achieve the highest conductivity of zirconia. The effect of ionic radius of divalent ions is more significant than that of lattice binding energy of divalent oxides for enhancing the ionic conductivity of zirconia co-doping system.
Grain size of Zr0.92Y0.16-XMXO2.08-0.5X systems increase with an increase of divalent oxide content. It seems that the grain size is correlated with the amount of oxygen vacancy. CaO and SrO segegated in grain boundaries when CaO and SrO contents are more than 0.015mole and 0.01mole respectively, because of the ionic radius of Ca2+ and Sr2+ are larger than that of Zr4+, the solid solution of CaO-ZrO2 and SrO-ZrO2 did not form easily. This is a reason why grain growth was restrained in higher CaO and SrO content.
The radii of oxygen vacancies in co-doped system were calculated from Hard-sphere model and the results show that oxygen vacancy radius depends on the ionic radius of the divalent dapants in Zr0.92Y0.16-XMXO2.08-0.5X system, the ionic conductivity of Zr0.92Y0.16-XMXO2.08-0.5X seems to increase as the oxygen vacancy radius increased. The trend of ionic conductivity increase, which is σMgYSZ>σCaYSZ>σSrYSZ, is similar to the trend of oxygen vacancy size increase, which is rVo(Mg)> rVo(Ca)> rVo(Sr).
The ionic conductivity of Zr0.920Y0.155M0.005O2.08-0.5X possesses outstanding electrical properties which is close to that of Ce0.8Sm0.2O1.9 which is 0.037(S•cm-1). For this reason, the Zr0.920Y0.155M0.005O2.08-0.5X is suit able to apply in the reduction-resistance layer of SDC electrolyte system for sandwich structure in SOFCs and decrease the operation temperature.

1. N. Q. Minh, T. Takahashi, “Science and technology of ceramic fuel cell.” Elsevier Science B. V. 11, 92~96 (1995).
2. K. Eguchi, “Ceramic materials containing rare earth oxides for solid oxide fuel cell”, J. Alloys. Compds., 250, 486-491 (1997).
3. H. Kaneko, F. Jin and H. Taimarsu, “Electrical conductivity of zirconia stabilized with scandia and yttria,” J. Am. Ceram. Soc., 76 [3] 793-795 (1993).
4. H. Yamamura, N. Utsunomiya, T. Mori, T. Atake, “Electrical conductivity in the system ZrO2-Y2O3-Sc2O3,” Solid State Ionics., 107 185-189 (1998).
5. H. Naito, H. Yugami, H. Arashi, “Electrical properties of ZrO2-In2O3-Y2O3 and its application to a membrane for gas separation,” Solid State Ionics., 90 173-176 (1996).
6. A. Tsoga, A. Naoumidis, W. Jungen and D. StÖver, “Processing and characterisation of fine crystalline ceria gadolinia – yttria stabilized zirconia powders,” J. Europ. Ceram. Soc., 19 907-912 (1999).
7. C. H. Lee and G. M. Choi, “Electrical conductivity of CeO2-doped YSZ,” Solid State Ionics, 135 653-661 (2000).
8. F. C. Fonseca, R. Muccillo, “Impedance spectroscopy of (yttria-stabilized zirconia)-magnesia ceramic composites,” Solid State Ionics., 131 301-309 (2000).
9. Y. Li, J. Gong, Y. Xie, Z. Tang and Z. Zhang, “Low-temperature ionic conductivity of the solid solution in the system ZrO2-Y2O3-Yb2O3,” Mater. sci. eng., B92 287-290 (2002).
10. J. H. Lee, S. M. Yoon, B. K. Kim, H. W. Lee and H. S. Song, “Electrical conductivity and defect structure of yttria-doped ceria-stabilized zirconia,” Solid State Ionics., 144 175-184 (2001).
11. J. Kimpton, T. H. Randle and J. Drennan, “Investigation of electrical conductivity as a function of dopant-ion radius in the system Zr0.75Ce0.08M0.17O1.92 (M=Nd, Sm, Gd, Dy, Ho, Y, Er, Yb, Sc),” Solid State Ionics., 149 89-98 (2002).
12. M. M. Bućko, “Ionic conductivity of CaO-Y2O3-ZrO2 materials with constant oxygen vacancy concentration,” J. Europ. Ceram. Soc., 24 1305-1308 (2004).
13. Y. Shiratori, F. Tietz, H. J. Penkalla, J. Q. He, Y. Shiratori, D. StÖver, “Influence of composites in the system (3YSZ)1-X-(MgO)X,” J. Power Sources., 148 (2005) 32-42.
14. E. Ponthieu, European fuel cell research, “development and Demonstrations : Future programmers and aims”, J. Power Sources, 72, 244 (1998).
15. www.netl.doe.gov/seca/ (2006)
16. S. Adler, Solid oxide fuel cells, Course Notes, “Department of Chemical Engineering”, University of Washington, (2003).
17. J. W. Yan, Z. G. Lu, Y. Jiang, Y. L. Dong, C. Y. Yu, W. Z. Li, “Fabrication and testing of a doped lanthanum gallate electrolyte thin film solid oxide fuel cell”, J. Electrochem. Soc. 149 (9) A1132–A1135 (2002) .
18. K. Ukai, Y. Mizutani, Y. Kume, “Current status of SOFC development using scandia doped Zirconia”, SOFC VII 375 (2001).
19. O. Marina, C. Bagger, S. Primdahl, M. Mogensen, “A solid oxide
fuel cell with a gadolinia-doped ceria anode: preparation and
performance”, Solid State Ionics. 123, 199–208 (1999)
20. M. Joerger, L. Gauckler, “Catalytically active anodes for SOFC”, SOFC VII, 662 (2001).
21. S. Livermore, J. Cotton, M. Ormerod, “Fuel reforming and electrical performance studies in intermediate temperature ceria-gadoliniabased SOFCs”, J. Power Sources 86 (2000) 411–416.
22. E. Batawi, Sulzer Hexis, (2003).
23. N. Kiratzis, P. Holtappels, C.E. Hartwell, M. Morgensen, J. T. S. Irvine, “Preparation and characterization of copper/yittria tatania zirconia cermets for use as possible solid oxide fuel cell anodes”, Fuel Cells 1, 211–218. (2001)
24. C. Lu, W. L. Worrell, R. J. Gorte, J. M. Vohs, “SOFCs for direct oxidation of hydrocarbon fuels with samaria-doped ceria electrolyte,” J. Electrochem. Soc. 150 A354–A358 (2003).
25. O. A. Marina, S. Primdahl, C. Bagger, M. Mogensen, “Ceria-based anodes on a YSZ electrolyte: preparation and electrochemical performance,” SOFC V 540 (1997).
26. M. Mori, T. Yamamoto, M. Mori, T. Horita, N. Sakai, H. Yokokawa, M. Dokiya, “Evaluation of Ni and Ti-doped Y2O3 stabilized ZrO2 cermet as an anode in high-temperature solid oxide fuel cells”, Solid State Ion. 160, 1–14 (2003)
27. J. M. Ralph, J. A. Kilner, B. C. H. Steele,” Improving Gd-doped ceria electrolytes for low temperature solid oxide fuel cells”, Mater. Res. Soc. Symp. Proc. 575, 309 (2001).
28. N. T. Hart, N. P. Brandon, M. J. Day, N. Lapena-Rey, “Functionally graded composite cathodes for solid oxide fuel cells”, J. Power Sources, 106, 42–50 (2002).
29. E. P. Murray, S. A. Barnett, “Improved performance in (La, Sr)MnO3 and (La, Sr)(Co, Fe)O3 cathodes by the addition of a Gd-doped ceria second phase”, SOFC VI , 369 (1999).
30. M. Krumpelt, J. Ralph, T. Cruse, Argonne activity overview,in: SECA Core Technology Review, SECA, Sacramento, CA, 2003.
31. S. Visco, C. Jacobson, L. De Jonghe, Thin-film Fuel Cells,Lawrence Berkeley National Laboratory, 1997.
32. O. Yamamoto, “Solid oxide fuel cells: fundamental aspects and prospects”, Electrochim. Acta 45, 2423–2435 (2000).
33. S. Wang, T. Kato, S. Nagata, T. Honda, T. Kaneko, N. Iwashita, M. Dokiya, “Performance of a La0.6Sr0.4Co0.8Fe0.2O3– Ce0.8Gd0.2O1.9–Ag cathode for ceria electrolyte SOFCs”, Solid State Ionics. 146, 203–210 (2002).
34. Y. Takeda, H. Ueno, N. Imanishi, O. Yamamoto, N. Sammes, M.B.Phillipps, “Gd1−xSrxCoO3 for the electrode of a solid oxide fuelcells,” Solid State Ionics. 86–88, 1187–1190 (1996).
35. H. Sung Yoon, D. Lee, B. Ho Kim, “Synthesis and characterization of Gd1−xSrxMnO3 cathode for SOFC,” SOFC VI, 493 (1999).
36. Z. Yang, J. Stevenson, P. Singh, Solid oxide fuel cells, Adv. Mater.Process. 161 (6) 34–37 (2003).
37. S.P.S. Badwal, “Stability of solid oxide fuel cell components”, Solid State Ionics. 14339–46 (2001).
38. W.Z. Zhu, S.C. Deevi,” Opportunity of metallic interconnects for solid oxide fuel cells: a status on contact resistance”, Mater. Res.Bull. 38 957–972 (2003).
39. S.C. Sinhal, “Solid oxide fuel cells for stationary, mobile, and military applications”, Solid State Ionics. 152–153, 405–410 (2002).
40. R. P. Ingel, D. Lewis, B. A. Bender, and R. W. Rice, “Physical, microstructural, and thermomechanical properties of ZrO2 single crystals”, pp.408-14 in Advances in ceramics, Vol. 12, Science and technology of Zirconia II. Edited by N. Claussen, M. Ruhle, and A. H. Heuer. American ceramic society, Clumbus, OH, (1984).
41. R. P. Ingel, D. Lewis, B. A. Bender, and R. W. Rice, “Temperature dependence of strength and fracture toughness of ZrO2 single crystals”, J. Am. Ceram. Soc., 65 [9], C-150-C-152 (1982).
42. D. Michel, L. Mazerolles, and M. Perez y Jorba, “Fracture of metastable tetragonal zirconia crystals”, J. Mater. Sci., 18, 2618-28, (1983).
43. 許崴棋，”異價離子共摻雜對氧化鋯與氧化鈰之晶體結構與導電性質之影響”，台灣科技大學材料科技研究所碩士論文，民國94年6月。
44. J. F. Baumard and P. Abelard, “In Science and Technology of Zirconia II”, N. Claussen, M. Rühle, and A. H. Heuer (eds.), American Ceramic Society, Columbus, OH , 555 (1984).
45. Y. Suzuki and T. Takahashi, J. Chem. Soc. Jpn, 1610 (1997).
46. N. H. Anderson, K. Claussen, M. A. Hackett, W. Hayes, M. T. Hutchings, J. E. Macdonald, and R. Osborn, “In Transport-Structure Relations in Fast Ion and Mixed Conductor,” F. W. Poulsen, N. H. Anderson, K. Clausen, S. Skaarup, and O. T. Sørensen (eds.), Risø National Laboratory, Roskilde, Denmark, p. 279 (1985).
47. A. Nakamura and J. B. Wagner, Jr., ” Defect Structure, Ionic Conductivity, and Diffusion in Yttria Stabilized Zirconia and Related Oxide Electrolytes with Fluorite Structure ,” J. Electrochem. Soc., 133 , 1542-48 (1986).
48. Y. Suzuki and K. Sugiyama, J. Ceram. Soc. Jpn. Intl. Ed., 95, 480 (1987).
49. E. C. Subbarao, in Science and Technology of Zirconia II, N. Claussen, M. Rühle, and A. H. Heuer (eds.), American Ceramic Society, Columbus, OH, p. 1 (1981).
50. J. H. Park and R. N. Blumenthal, “, Electronic Transport in 8 Mole Percent Y2O3-ZrO2” J. Electrochem. Soc., 136 2867 (1989).
51. W. Weppner. In Proceedings of the International Symposium on solid Oxide Fuel Cells. November 13~14, 1989, Nagoya, Japan, Yamamto O, Dokiya M, Tagawa H eds. Science House, Tokyo, Japan, 1989:83
52. W. Weppner, H. Schuber. Science and Technology of Zirconia
Ⅲ.Somiya S,Yamamoto N, Yanagda H(eds).American Ceramic Society, Westerville, OH, 1988:837.
53. Pimenov, J. Ullrich, P. Lunkenheimer et al. “Enhanced specific grain
boundary conductivity in nanocrystalline Y2O3-stabilized zirconia”. Solid State Ionics, 108, 111~118 (1998).
54. R. Ramamoorthy, D. Sundararaman, S. Ramasamy. “Ionic conductivit studies of ltrafine- grained yttria stabilixed zirconia polymorphs.”Solid State Ionics, 123, 271-278 (1999).
55. P. Mondal, A. Klien, W. Jaegermann, H. Hahn.”Ionic conductivity and relaxation in ZrO2-Y2O3 solid solutions.” Solid State Ionics ,
118:331-339 (1999).
56. G. Dotelli, R. Volpe, Natali-SoraⅠet al.”Impedance apectra simulation of yttria-stabilized zirconia/alumina composites,”Solid State Ionics, 113~115:277-283 (1998).
57. F. Ishizaki, T. Yoshida, S. Sakurada.In :Proceedings of the International Symposium on Solid Oxide Fuel Cell.November 13-14, 1989, Nagoya, Japan, O. Yamamoto, M. Dokiya, and H. Tagawa(eds). Science House : Tokyo, Japan, 172~176 (1998).
58. F. J. Esper, K. H. Friese, H. Geier. In Science and Technology of
ZirconiaⅡ.Clausen N, Ruhle M, Heuer A H eds.American Ceramic
Society:Columbus, OH, P528 (1984).
59. Yuzaki, A. Kishimoto, Y. Nakamura.”Effect of alumina-dispersion on
ionic conduction of toughened zirconia base composite.” Solid State
Ionica, 116, 47-51 (1999).
60. Y. Ji, J. Liu, Z. Lu et. ”Study on the properties of Al2O3-doped (ZrO2)0.92(Y2O3)0.08 electrolyte.”, Solid State Ionics, 126, 277-283 (1999).
61. A. J. Feighery, J. T. S. “Irvine.Effect of alumina addition upon electrical properties of 8mole% yttria-stabilized zirconia.” Solid State Ionics, 121:209-216 (1999).
62. J. F. Baumard and P. Abelard. In Science and Technology of Zirconia Ⅱ.Clausen N, Ruhle M, Heuer A H eds. American Ceramic Society, Columbus, OH, P555 (1984).
63. M. Yashima, M. Kakihana, M. Yoshimura. ”Metastable-stable phase
diagrams in the Zirconia-containing systems utilized in solid-oxide fuel cell application.” Solid State Ionics, P86~88: 1131-1149 (1996).
64. M. Hirano, S. Watanabe, E. Kato et al.”Fabrication,electrical
conductivity and mechanical properties of Sc2O3-doped tetragonal
zirconia ceramics.”, Solid State Ionics, 111, P161-169 (1998).
65. Y. Li, Z. Tang, Z. Zhang, and J.Gong,”Electrical conductivity of zirconia stabilized with yttria and calcia.”J.Mat.Sci.Lett.,6,443-444,
(1999).
66. H. Yamamura, N. Utsunomiya, T. Mori, T. Atake. ”Electrical conductivity in the system ZrO2-Y2O3-Sc2O3.”, Solid State Ionics, 107, 185-189 (1998).
67. S.P.S. Badwal,F.T. Ciacchi,S.Rajendran et al. ”An investigation of
conductivity,microstructure and stability of electrolyte composisions
in the system 9%(Sc2O3-Y2O3)-ZrO2(Al2O3)”. Solid State
Ionics,1998,109,167~186.
68. O. Yamamoto, Y. Takeda, N. Imanishi. T. Kawahara, G. Q. Shen, M. Mori. and T. Abe, “Electrical and Mechanical Properties of Zirconia-Alumina Composite Electrolyte”, 437-44 (1993).
69. X.J. Chen, K.A. Khor,” Influence of microstructure on the ionic conductivity of yttria-stabilized zirconia electrolyte”, Materials Science and Engineering, A335, 246–252 (2002).
70. Lide and David, “CRC Handbook of Chemistry and Physics: Ed. 71”, Boca Raton: CRC Press, (1990).
71. 陳俊偉，”固態氧化物燃料電池氧化鋯電解質之韌性與金屬雙極板抗氧化性研究”，台灣科技大學機械工程系碩士論文，民國94年6月。
72. Masatoshi Hattori, Yasuo Takeda,” Effect of aging on conductivity of yttria stabilized zirconia”, J. power sources, 126, 23-27 (2004).
73. M.Yashima, N.Ishizawa, M.Yoshimura, “ Application of an Ion Packing Model Based on Defect Clusters to Zirconia Solid Solution：I, Modeling and Local Structure of Solid Solution”, J. Am. Ceram. Soc., 75[5] 1541-49 (1992)
74. M.Yashima, N.Ishizawa, M.Yoshimura, “ Application of an Ion Packing Model Based on Defect Clusters to Zirconia Solid Solution：II, Modeling and Local Structure of Solid Solution”, J. Am. Ceram. Soc., 75[5] 1550-57, (1992)