BaO-B2O3-SiO2-Al2O3玻璃系統使用在中溫型固態氧化物燃料電池適宜性之研究

Abstract

BaO-B2O3-SiO2-Al2O3 玻璃系統已被廣泛接受可作為適用在操作溫度為800oC的中溫型固態氧化物燃料電池中的柔性封裝接合材。在材料設計考量方面，玻璃轉換溫度、熱膨脹係數、與燃料電池中其他零組件的化性及物性的匹配性、穩定性皆為適用材料選擇之決定性因素也是影響整個燃料電池的成敗性因素之一。在本研究中主要分成三個主題，首先是玻璃之合成與性質測定包括基本熱性質以及其結晶行為、潤濕行為之觀察；第二，為玻璃結晶動力學之探討，使用了Kissinger關係式以及Piloyan測定法進行結晶活化能和結晶成長機制之計算與分析；最後為與8YSZ和SDC接合界面行為之觀察。結果顯示47BaO-21B2O3-27SiO2-5Al¬2O3 (G1A5)具有良好的玻璃形成性（Glass-Forming-Ability），其玻璃工作溫度範圍為547-694oC（Tg-Tc）與中溫型固態氧化物燃料電池的操作溫度(600-650oC)相符合；在G1A5玻璃中，hexacelsian和BaSiO3為主要生成結晶相，其結晶活化能分別為423±38 kJ/mol和363±190 kJ/mol；在與8YSZ接合部份，G1A5玻璃雖無法與其有良好匹配且有殘留熱應力所導致之裂縫出現，但G1A5卻能與SDC達到良好的匹配性，在長時間使用下（100小時）仍具有良好的接合性質，也無裂縫或結晶相在介面處或玻璃內部生成。另一方面，在本研究中也發現53BaO-12B2O3-34SiO2-1Al¬2O3 (G6) 玻璃可與8YSZ達到長時間的良好接合性。

Several formulations of the glass based on BaO-B2O3-SiO2-Al2O3 systems have been developed and accepted as an appropriate compliant sealing material for planar Solid Oxide Fuel Cells (SOFC) operated at 800oC. The sealing materials in this study are designed by considering lower Tg (glass transition temperature) slightly than the set operation temperature (600-650oC), small CTE mismatch, chemically and physically compatible with the other components, and good wettability with specified substrates. Three main subjects are investigated in this study. The first one is the synthesis and characterization of the glasses, including thermal properties and crystallization behavior. The second is the investigation on crystallization kinetics by using Kissinger equation and Piloyan plot. Third one is to analyze the interfacial stability of the glass with 8YSZ or SDC. Differential thermal analysis (DTA) and Thermal Mechanical Analysis (TMA) were applied to study the thermal properties of the glass. X-ray diffraction (XRD) analysis was conducted to study the crystallization behavior. Scanning and transmission electron microscopes (SEM and TEM) with energy dispersive spectroscopy (EDS) were employed to observe the microstructure and phase evaluation. The results show that 47BaO-21B2O3-27SiO2-5Al¬2O3 (G1A5) possess better glass forming ability (GFA) than other formulation, and has the matched working temperature range (547-694oC) close to the operation temperature 600-650oC of IT-SOFC . The major crystalline phases that would precipitate from the glass matrix during IT-SOFC operation were hexacelsian and BaSiO3. The activation energies for each crystalline phase are 423±38 kJ/mol and 363±19 kJ/mol. When it comes to sealing with 8YSZ, although G1A5 glass can not have a good bonding property with 8YSZ, but it can seal very well with SDC, even after long-term thermal treatment (100 hr at 650oC). On the other hand, in this study we also found out another glass formulation, 53BaO-12B2O3-34SiO2-1Al¬2O3 (G6) can have a good bonding behavior with 8YSZ.