釩、鈣共摻雜氧化鉍離子導電材料之合成與用於固態燃料電池陰極之性能研究

Abstract

本研究探討釩、鈣共摻雜之氧化鉍材料具有之混合電子、離子導體之合成特性與應用於中溫型固態燃料電池陰極之電性表現。本研究總摻雜量在13 mol%以下，並以X光繞射、熱分析、兩點及四點直流電量測、X光電子能譜及掃瞄電子顯微鏡技術予以分析。本研究並對釩摻雜量少於13 mol%的鉍釩相圖做進一步的修正，包含γ相之相界與未報導之7:1相。結果顯示少量之釩、鈣共摻雜的氧化物B8VC(0.5:0.5) 之導電度結果在650oC之導電度為0.013 Scm-1。除了全導電率，離子導電度也在本研究裡予以測量，其結果顯示鉍釩氧化物為混合電子離子導體。另外，X光電子能譜(XPS)分析出釩離子除五價外尚有三價與四價釩的存在，間接證明混合導體的特性。最後，B8VC(0.5:0.5)導體應用在固態燃料電池之陰極在800oC之電池電功率輸出為395 mWcm-2，較之以鑭鍶鈷鐵(LSCF6428)做為陰極之標準電池的電功率輸出(353mWcm-2)高出約10%。

This work synthesizes Bi-V-(Ca)-O materials and investigates the properties of the cells with Bi-V-(Ca)-O cathode. Total concentration of V and Ca dopants is less than 13 mol%. The samples have been characterized by X-ray diffraction (XRD), thermal analysis, 2-probe and 4-probe DC measurements, X-ray photoelectronic spectrum (XPS), and scanning electron microscopy. The results allow us proposing a new revision of Bi2O3-V2O5 phase diagram in the region less than 13 mol% V2O5. The electrical conductivities show that B8VC(0.5:0.5) shows the highest electrical conductivity, 0.013 Scm-1 at 650oC among the prepared samples. Besides, the ionic conductivities of the Bi-V-O materials show mix-electronic-ionic (MEI) property. Moreover, XPS analysis shows the coexistence of 3+ and 4+ vanadium ions with 5+ ions, which prove the presence of MEIC property indirectly. Besides, the power density of the cell with B8VC(0.5:0.5) cathode is 395 mWcm-2 at 800oC, which is 10% higher than that, 353 mWcm-2, of standard-cell with LSCF6428 cathode.