使用溶液燃燒法合成新式中溫型固態氧化物燃料電池陰極材料Ba0.5Sr0.5CuxFe1-xO3-δ

Synthesis of Novel Cathode Materials Ba0.5Sr0.5CuxFe1-xO3-δ for IT-SOFC by Solution Combustion Methode

林彥廷(Yen-Ting Lin)

指導教授 ： 余炳盛

國立臺北科技大學/工程學院/資源工程研究所/碩士(2009年)

https://doi.org/10.6841/NTUT.2009.00637

摘要

BaySr1-yCoxFe1-xO3-δ為眾多中溫型固態氧化物燃料電池(IT-SOFC)中發電效率最高之陰極材料，但BaySr1-yCoxFe1-xO3-δ仍有：熱膨脹係數高、導電度低、材料價格昂貴等缺點。故本研究使用銅取代鈷成為新型Ba0.5Sr0.5CuxFe1-xO3-δ IT-SOFC陰極材料。
本研究使用溶液燃燒法合成Ba0.5Sr0.5CuxFe1-xO3-δ，研究內容包含：1.陰極材料之合成及2.陰極材料性質探討，研究結果顯示使用GNP法能有效縮短合成時間及降低合成溫度，產物經ICP-AES分析，證實其成份與原始化學劑量比相同，當銅的添加量大於x=0.3時無法成功合成純鈣鈦礦結構之陰極材料。燃料比由低至高使前驅物產生三種不同的燃燒模式，分別為悶燃、自蔓反應以及體積燃燒反應，當燃料比為2且pH值為2.3時為最佳合成條件。此外本研究也使用EDTA-Glycine法合成Ba0.5Sr0.5Cu0.2Fe0.8O3-δ-BaCeO3複合陰極材料，研究結果顯示加入EDTA能幫助前驅物錯合反應，故較GNP法有更寬廣的合成條件(pH4~9)，但需加入氧化劑硝酸銨才能幫助其前驅物行自蔓燃燒反應。
材料性質探討方面，由實驗結果可得知陰極材料之熔點隨著銅的摻雜量增加而降低，當摻雜量為x=0.3時，熔點降低至868℃。本研究選用3種常見之電解質材料SDC、GDC、YSZ與Ba0.5Sr0.5Cu0.2Fe0.8O3-δ進行化學匹配實驗，由結果顯示GDC與Ba0.5Sr0.5Cu0.2Fe0.8O3-δ之匹配度最高，經900℃熱處理後仍無二次相的產生。在材料導電度方面可觀察到，Ba0.5Sr0.5CuxFe1-xO3-δ(x=0.3-0.1)之導電度並不會隨著銅的摻雜量增加而呈線性增加，其中以銅的摻雜量為0.2的條件下導電度最高，當操作溫度為346℃時導電度最高，達到127.46 S/cm。在材料燒結行為方面可觀察到，當燒結溫度超過材料熔點時，銅擴散至表面，會由晶界處析出而形成氧化銅。
Ba0.5Sr0.5Cu0.2Fe0.8O3-δ能在較低的操作溫度下擁有高的導電效率，且具低溫製程及降低材料價格之優勢，故Ba0.5Sr0.5Cu0.2Fe0.8O3-δ亟具潛力發展成為中溫型固態氧化物燃料電池之新陰極材料。

關鍵字

固態氧化物燃料電池 ； 陰極材料 ； 鈣鈦礦 ； 溶液燃燒法

並列摘要

BaySr1-yCoxFe1-xO3-δ is considered to be one of the best cathode materials for IT-SOFC. The material, however, has also been found to carry with it several disadvantages, notably high thermal expansion coefficient, low conductivity, and high cost. The study accordingly uses copper to replace cobalt to develop a new cathode material Ba0.5Sr0.5CuxFe1-xO3-δ for IT-SOFC.
The objective of the study is two-fold: 1.Synthesis of pure Ba0.5Sr0.5CuxFe1-xO3-δ perovskite; and 2. Discussion of the material’s chemical and physical properties. Ba0.5Sr0.5CuxFe1-xO3-δ perovskite was synthesized by solution combustion. As indicated by the results, glycine-nitrate-process (GNP) was able to shorten the time of synthesis and reduce the calcination temperature. Pure cubic perovskite products were observed in X-ray diffraction (XRD) measurement with Cu-dopping at X = 0.1 to 0.3. And the composition of the products was confirmed using ICP-AES. It was also observed that, as the G/M ratio rose, three different combustion modes occurred respectively: volumetric combustion, self-propagating combustion, and smothering combustion. The situation at G/M=2 and pH=2 was identified to be the best condition for synthesizing Ba0.5Sr0.5CuxFe1-xO3-δ.
Moreover, the study also adopted EDTA-glycine combustion method to prepare Ba0.5Sr0.5CuxFe1-xO3-δ - BaCeO3 perovskite. This method boasts an extensive synthesis range, so Ba0.5Sr0.5CuxFe1-xO3-δ - BaCeO3 could be synthesized at pH from 4 to 11. Moreover, adding NH3NO2 was found to be good for combustion reaction.
In this study, chemical stability with electrolyte, conductivity, and sintering behavior were examined. Cu-doping appeared to decrease the melting point of the synthesized material. Of the three common electrolytes (GDC, SDC, and YSZ), GDC was found to work best with Ba0.5Sr0.5CuxFe1-xO3-δ in achieving high chemical stability. The best conductivity of 127.46 S/cm was achieved when the temperature was 346℃ and X=0.2. Copper would diffuse to the surface when the sintering temperature rose above the melting point of the synthesized material.
The study finds Ba0.5Sr0.5CuxFe1-xO3-δ compounds capable of sustaining high conductivity at low temperature. Its ability to reduce synthesis temperature and material cost makes Ba0.5Sr0.5CuxFe1-xO3-δ a promising new cathode material for IT-SOFC.

並列關鍵字

SOFC ； cathode ； perovskite ； solution combustion

參考文獻

1. 張晏韶，以微波加熱燃燒合成法製備異質摻雜CeO2 固溶體粉末應用於固體氧化物燃料電池中固態電解質之研究，碩士論文，國立成功大學資源工程學研究所，台南，2004。

3. M.C. Wiliams, Solid oxide fuel cells：Fundamentals to systems, Fuel cell, 2007 pp.78-85.

6. Q.L. Liu, K.A. Khor, S.H. Chan, " High-performance low-temperature solid oxide fuel cell with novel BSCF cathode ", Journal of Power Sources, vol.161 , 2006, pp. 123-128.

12. S. Saha, S. J. Ghanawat, R. D. Purohit, " High-performance low-temperature solid oxide fuel cell with novel BSCF cathode ", J MATER SCI, vol.41, 2006, pp. 1939-1943.

13. 吳俊德，以化學共沉法製備鑭銦(鎵)鋯氧化物及其性質之研究，碩士論文，國立成功大學化學工程研究所，台南，2003。