釔安定氧化鋯(YSZ)為一最常使用之離子導體，其機械強度及相穩定性高，但燒結溫度必須高達1500℃才可獲得緻密之結構，如此的高溫限制了該材料的應用亦增加了製造成本。釔安定氧化鉍(YSB)與釔安定氧化鋯同為CaF2結構，且燒結溫度(~900℃)遠低於氧化鋯之燒結溫度，加上導電率是YSZ的10倍以上，所以本研究欲藉由YSB的添加，一方面降低YSZ的燒結溫度，另一方面增加其導電率，同時探討YSB添加劑對YSZ晶體結構、燒結緻密性、離子導電率以及機械強度的影響。
　　本實驗是以固態反應法合成試片，所使用的基材為8YSZ(8 mol% Y2O3-92 mol% ZrO2)，添加劑為25YSB(25 mol% Y2O3-75 mol% B2O3)。實驗結果發現，添加YSB可使YSZ的燒結溫度降至1000~1200℃。在結構方面，主相仍為立方結構之富YSZ相，當YSB添加量為5~15 mol% 時，會形成正方結構之富Bi2O3第二相；添加量在5 mol% 以下則有些許ZrO2單斜相出現。其中，富YSZ相之晶格常數隨YSB添加量的增加而提升。
　　在燒結緻密性方面，相同1000℃的燒結條件下，純YSZ的孔隙率高達44.7%，直徑收縮率僅4.9%；添加10 mol% YSB之後，試片孔隙率僅0.85%，收縮率達18.4%。隨YSB添加量愈高，試片之開孔孔隙率愈小、直徑收縮率愈大，但過多的YSB添加量(15%)會導致試片內部散佈有許多巨大的空孔。YSB對YSZ燒結行為的影響，推測是燒結過程中，
Y3+、Bi3+、Zr4+ 於YSZ與YSB之間相互擴散，造成原本的YSB組成改變，形成一富Bi2O3第二相，由於富Bi2O3相的熔點低於燒結溫度，因此燒結的過程是以液相的機制進行。
　　在導電率方面，由於富Bi2O3相分布於晶粒周圍，其650℃~750℃之間會由正方結構轉變為高導電率的立方結構，因此添加YSB之試片在700℃以上之導電率，皆高於1500℃燒結之純YSZ的導電率；而試片在700℃以下之導電率，則隨YSB添加量的增加而下降，其原因在於富YSZ相的Y/Zr比例皆大於具有最大導電率之Y/Zr值，而YSB添加量愈多Y/Zr值愈大，因此導電率愈低。

　　Yttria stabilized-zirconia oxide (YSZ) is the most commonly used ionic conductors especially for SOFC applications. YSZ has the excellent mechanical strength and stability, but its high sintering temperature limits many application. Yttria-stabilized bismuth oxide (YSB) has the same crystal structure as YSZ but lower melting point and higher conductivity compared to it.
　　In the present study, we tried to reduce the sintering temperature and to increase the ionic conductivity of YSZ by the addition of YSB. As the result, the sintering temperature of YSZ was reduced to 1000℃ by doping adequate amount of YSB. For the YSB-doped YSZ samples, the majority phase was Y-rich YSZ with the cubic structure. The lattice constant of Y-rich YSZ phase increased with increasing YSB concentration. The Bi-rich second phase with tetragonal structure were found in the 5~15% YSB-doped YSZ samples.
　　Under the same sintering condition (1000℃、5hrs), the apparent porosity of pure YSZ specimens was as high as 44.7%. For the 10 mole% YSB-doped YSZ, its porosity was only 0.85%. The higher concentration of YSB, the lower apparent porosity of specimens. When the addition of YSB was more than 15%, the large pores would appear in the specimens. The densification of YSB-doped specimens at 1000℃ was due to the presence of liquid phase sintering. The formation of liquid phase was caused by the liquidification of Bi-rich phase at 800~900℃.
　　For the conductivity measurement at temperatures＞700℃, the YSB-doped YSZ sintered at 1000~1200℃ had the higher conductivity than pure YSZ specimens sintered at 1500℃. The main reason is due to the presence of high conductivity cubic Bi2O3-based phase above 700℃. Below 700℃, the conductivity of YSB-doped specimens decreased with increasing YSB concentration. It was because the Y/Zr value of YSZ-rich phase was beyond 8 mol% which gave the best conductivity.

【1】T.H. Etsell and S.N. Flengas, J. Electrochem. Soc., 119, p1, 1972
【2】 楊志忠、林頌恩、韋文誠, 燃料電池的發展現況, 科學發展, 367期, p30~33, 2003年
【3】 左峻德, 燃料電池之特性與運用, 行政院國家科學委員會科學技術資料中心, 2001年
【4】 S.C. Singhal, "Status of solid oxide fuel cell technology," Proceedings of the 17th, Riso International Symposium on Material Science, High Temperature Elcctrochemistry, Ceramics and Metals, Roskilde, Denmark, Sept. 1996.
【5】 D.H. Archer, J.J. Alles, W.A. English, L. EliKan, E.F. Sverdrup and R.L. Zahradnik, in：Westinghouse Solid-Electrolyte Fuel Cell, Fuel
Cell Systems, p332-342
【6】 S.C. Singhal, "Science and technology of solid oxide fuel cells," MRS Bulletin, pp. 16-20, March 2000.
【7】 N.Q. Minh, "Ceramic fuel cell," J.Am.Ceram. Soc.,76 [3], p563-588, 1993.
【8】 A.H. Heuer and M. Rühle, "Science and technology of zirconia II," Advances In Ceramics, vol.12, p2-3, 1984
【9】 M.M. Nasrallah and D.L. Douglas, J. Electrochem. Soc., 6, p255, 1974
【10】 G.M. Wolten, "Diffusionless phase transformations in zirconia and hafnia," J. Am. Ceram. Soc., 46 [9 ], p418-22, 1963
【11】 T.H. Etsell and S.N. Flemgas, "Electrical properties of solid oxide electrolytes," Chem. Rev., 70[3], p339, 1970
【12】 E.C. Subbarao; in：Advances in Ceramics, Edited by A. H. Heuer and L.W. Hobbs., The American Ceramic Society, Columbus, OH, vol.3, p1-24, 1981
【13】 S.P.S. Badwal, "Zirconia-based solid electrolytes: microstructure, stability and ionic conductivity," Solid State Ionics, 52, P23-32, 1992
【14】 P. Shuk , H.D. Wiemhofer, U. Guth, W. Gopel, and M.Greenblatt, "Oxide ion conducting electrolytes based on Bi2O3," Solid State Ionics, 89, p179-196, 1996
【15】 R.K. Datta, and J.P. Meehan, "The system Bi2O3-R2O3(R=Y, Gd)," Zeitschrift für Anorganishe und Allgemeine Chemie, 383, p328-337, 1971
【16】 T. Takahashi, H. Iwahara and T. Arao, "High oxide ionconducting in sintered oxides of the system bismuth (III) oxide-yttrium oxide," J. Appl. Electrochem., 5, p187-195, 1975
【17】. T. Takahashi and H. Iwahara, "Oxide ion conductors based on bismuth sesquioxide," Materials Research Bulletin, 13, p1447-1453 , 1978
【18】. T. Takahashi, T. Esaka and H. Iwahara., J. Appl. Electrochem., 7, P303, 1977
【19】. R.D. Shannon, Acta. Cryst., A32, p751, 1976
【20】. M. Miyayama and H. Yanagida, "Oxygen ion conduction in fcc Bi2O3 doped with ZrO2 and Y2O3," Mat. Res. Bull., 21, p1215-1222, 1986
【21】 P.S. Duwez, F.H. Brown, Jr. and F. Odell, J. Electrochem. Soc., 98, p360, 1951
【22】 Watanabe, A., "Phase equilibria in the system Bi2O3-Y2O3：no possibility of δ-Bi2O3 stabilization," Solid State Ionics, 86-88, p1427-
1430, 1996
【23】 M.J. Verkerk and A.J. Burggraaf, "High oxygen ion conduction in sintered oxides of the Bi2O3-Dy2O3 system," J. Electrochem. Soc., 128, p75-82, 1981
【24】 E.M. Levin and R.S. Roth, J. Research Natl. Bur. Stardands, 68A [2], p201, 1964
【25】 Isaac Abrahams, Alexandra J. Bush, Simon C. M. Chan, Franciszek Krokb and Wojciech Wrobelb, "Stabilisation and characterisation of a new ßIII-phase in Zr-doped Bi2O3," J. Mater. Chem., 11, p1715-1721, 2001
【26】 H. Schmalzried, "On correlation effects of vancancies in ionic crystals," Z. Phys. Chem. (Wiesbaden), 105, p47-62, 1977