Investigations on the Environmental and Electrochemical Stability of the Mixed Ionic/Electronic Conducting Alkaline-Earth Ferrite Membrane

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Project title

Code/計畫編號

MOST104-2221-E019-005

Translated Name/計畫中文名

鹼土鐵系混合電子/離子導電膜之環境與電化學穩定性研究

Project Coordinator/計畫主持人

Horng-Yi Chang

Funding Organization/主管機關

National Science and Technology Council

Department/Unit

Department of Marine Engineering

Website

https://www.grb.gov.tw/search/planDetail?id=11578659

Year

2015

Start date/計畫起

01-08-2015

Expected Completion/計畫迄

31-07-2016

Bugetid/研究經費

923千元

ResearchField/研究領域

化學工程

"不含鈷的Ba0.5Sr0.5FeO3-(BSF)為結合CeO2基電解質之IT-SOFC的極佳陰極材料。含Fe的ABO3-鈣鈦礦結構的電子導電率是由Fe4+/Fe3+變價，高氧離子導電率是由於較低B-O鍵結能與在各種配位多面體間的離子轉移，在高溫、高濕度、低氧分壓時，結構極不穩定。為了提升BSF的總導電度與結構穩定性，本研究首先進行Nb成份的摻雜，Nb預期將進入B位置取代Fe，穩定Fe之過度變價。Ce摻雜含Fe的ABO3- 可以形成立方結構而降低其熱膨脹係數(TEC)。大部份MIEC膜在CO2氣氛下抵抗形成碳酸鹽的能力，由A成份為La>Ca>Sr>Ba。本研究將設計La/Ce成份的半有機溶液(水/醇混合液)對BSF粉體顆粒進行殼層披鍍形成核-殼結構，探討Ce進入BSF的A或B位置？藉由控制反應溫度調整電解質與電極材料之界面反應，形成La/Ce殼層包覆BSF大粒子的核-殼結構，希望在BSF晶粒表面進行氣體擴散時即能防止濕度侵蝕及CO2碳酸鹽化，增進BSF對環境的穩定性，降低界面電阻，擴大陰極的TPB有效接觸表面積，增進電池的功能。"The Ba0.5Sr0.5FeO3-δ (BSF) without cobalt composition is an excellent cathode material to pair with the CeO2-based electrolyte. The electronic conductivity of AFeO3-δ perovskite originates from the valence change of Fe4+/Fe3+, and the high ionic conductivity comes from the low Fe-O bonding energy and the ions hopping among coordinate polyhedra. However, it exhibits structural instability under high humility, low oxygen partial pressure or at high temperature. In this proposal, the Nb species will be doped into BSF to promote the total conductivity and structural stability. It is expected that the Nb will replace the Fe in B-site to prohibit the excessive valence change of Fe. The Ce species doping into the AFeO3-δ perovskite can be benefit in the cubic phase formation as to lower the temperature expansion coefficient (TEC). The ability resistant to form carbonates in CO2 atmosphere is La>Ca>Sr>Ba sequentially in the A-site of most of the mixed ionic and electronic conductors (MIEC). In this study, the semi-organic solution (water/alcohol mixture) containing La/Ce composition is designed to coat the BSF powders to become core-shell particles. An investigation is the Ce diffusion into A- or B-site of perovskite. The interface reaction between electrolyte and electrode material is controlled by temperature regulation to form the La/Ce shell coverage on BSF core particles. The core-shell structure is expected to prohibit the BSF grains from the humility attack and carbonates formation from CO2 when the air diffusion on the BSF grains surface. Then, the environmental stability increase, interface area resistance lowering, and TPB effective contact area extending in the BSF cathode material will be achieved to improve the fuel-cell performances.

Keyword(s)

含Fe 鈣鈦礦
摻雜
核-殼結構
環境穩定性
Fe-contained perovskite
doping
core-shell structure
environmental stability

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Investigations on the Environmental and Electrochemical Stability of the Mixed Ionic/Electronic Conducting Alkaline-Earth Ferrite Membrane

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