摻雜型鉍鐵基鈣鈦礦材料用於中溫固態燃料電池陰極之研究

Abstract

本研究探討了鎳、錳、鈷摻雜之鐵酸鉍鍶（Bi0.7Sr0.3FeO3-δ）鈣鈦礦材料之合成特性，電性與應用於中溫固態燃料電池陰極之電性表現。以EDTA-檸檬酸法合成不同摻雜量的粉末，利用X光繞射法(XRD)確定不同元素摻雜的固溶極限，利用能量色散X射線光谱(EDS)進行定量成分分析，探究合成粉末的均勻性，利用热機械分析量測試樣的熱膨脹係數。以兩點及四點直流電量測，X射线光电子能谱分析（XPS）及熱重分析(TGA)探討材料的導電特性以及氧成份的非當量比。結果顯示鎳的固溶極限為3 at%，而錳的固溶量至少為50 at%，鉍鐵基試樣的熱膨脹係數都約在(13.1±0.38 )x10-6 K-1，接近于氧化鈰且明顯低於鑭鍶鈷鐵（LSCF6428）。電性的結果顯示錳的摻雜明顯提高了總導電性。採用四點式量測离子导电率，其中Bi0.7Sr0.3FeO2.95-0.022 在800 oC的离子导电率为4.21 x10-3 S.cm-1。 以乾壓法製備300 μm陽極,以旋渡法（spin-coating）在陽極製備微米平坦層，電解質層及陰極層組裝為單電池，以交流阻抗（EIS）分析有無平坦層與不同燒結溫度下陰極之界面極化電阻與接觸電阻。其中一組電池含Bi0.7Sr0.3Fe0.5Mn0.5O2.88-0.03 +20 SDC 陰極在800 oC之輸出為119 mW.cm-2.

The effects of nickel, cobalt and manganese doping in bismuth-based ferrite perovskite (Bi0.7Sr0.3FeO3-δ) used as cathode of solid oxide fuel cells have been investigated in this study. The cathode powders were synthesized by EDTA-citric acid method. The phase purity of synthesized perovskites were analyzed by X-ray Diffraction (XRD). The solubility limit of Ni was 3 at%, while Mn can substitute for Fe at least 50 at% in BSF. Electrical conductivity by 2-probe and 4-probe DC methods showed that the 50 mol% doping of Mn on B-site improved the electrical conductivity significantly. The oxygen nonstoichiometry was analyzed by X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) to reveal the deficiency of oxygen and ionic conductivity in the ferrites. The ionic conductivity of BSF was 4.21 x10-3 S.cm-1 at 800 oC. Anode disk of 300 μm thick coated with thin layer (μm layer thickness) of electrolyte by spin-coating method. The polarization resistance and contact resistance of the half-cell with an 8YSZ-N flat layer and cathode sintered by different sintering temperatures were analyzed by electrochemical impedance spectra analysis (EIS). Finally, the optimal cathode (Bi0.7Sr0.3Fe0.5Mn0.5O 2.88-0.034+20 SDC) was assembled to a full cell and the maximum power output was 119 mW.cm-2 at 800 oC.