摻雜異價離子(Y3+, Nb5+)氧化鉍基固態氧化物電解質電性與微結構之研究

The electric properties and microstructure analysis of aliovalent ions (Y3+, Nb5+) doped bismuth-based solid oxide electrolyte

張耀文(Yao-Wen Chang)

指導教授 ： 吳玉娟

國立臺北科技大學/工程學院/材料科學與工程研究所/碩士(2011年)

https://doi.org/10.6841/NTUT.2011.00488

摘要

本研究以固態合成法製備出氧化鉍基材摻雜氧化釔、氧化鈮，使氧化鉍螢石結構穩定於室溫中，以獲得良好特性之固態氧化物電解質。其目標在於發展中溫型固態氧化物燃料電池，操作溫度較低於目前商業化釔安定氧化鋯電解質有利於成本降低之優點。因自身不需摻雜異價離子即含25%之氧離子空缺之特點，屬缺陷型螢石結構，也藉此特點而具有極優良之離子傳導性質。
實驗以單摻雜Y2O3與Nb2O5之方式，摻雜系統為Bi1-xYxO1.5與Bi1-yNbyO1.5+δ，分別以摻雜量x = 0.20~0.30，y = 0.15~0.25。燒結條件設定在800~950oC並持溫兩小時，來觀察溫度變化對性質之影響。分析方面以XRD、SEM、Raman、TEM、直流、交流阻抗與熱膨脹係數來觀察各條件下之性質與結構特徵。經燒結後藉由XRD判別試片所屬結構皆呈螢石結構(Fm‾("3" )m)繞射訊號。藉SEM觀察試片隨著燒結溫度提高，使晶粒成長而緻密化。YSB系統中，30YSB/800oC晶粒尺寸為0.59 μm，並在20YSB/950oC晶粒達到10.63 μm；NDB系統中，較為前系統晶粒尺寸略大，25NDB/850oC時晶粒尺寸為0.49 μm，並在15NDB/950oC時成長至29.35 μm。拉曼結構鑑定YSB系統特徵峰出現在110.7 cm-1、617.3 cm-1之頻率；而NDB系統在前段波數分別為96 cm-1、145 cm-1與後段740.6 cm-1則證實其為螢石結構之訊號。在此次直流電阻分析實驗中，20YSB/950oC有最佳離子傳導性，20YSB/800oC試片在800oC時導電度為0.75 S/cm，燒結溫度為950oC於800oC時則有導電性1.97 S/cm；在NDB系統中，15NDB/800oC試片在800oC時導電度為0.38 S/cm，並在燒結溫度為950oC於800oC時電性微幅提升至0.41 S/cm。在交流阻抗實驗中可觀察到，YSB與NDB系統皆在量測溫度提升時，阻抗有下降之表現。TEM顯微分析中，可由擇區繞射影像發現不同的額外繞射點訊號，並藉TEM高解析影像觀察到Type II、Type III之兩種結構共存於25NDB/950oC試片中。熱膨脹分析中經摻雜後20YSB/800oC於600oC時熱膨脹係數為22.6×10-6/oC，摻雜至30YSB/800oC於600oC時熱膨脹係數為20.6×10-6/oC；15NDB/800oC於600oC時熱膨脹係數為19.5×10-6/oC。

關鍵字

固態氧化物燃料電池 ； 固態電解質 ； 氧化鉍 ； 缺陷型螢石結構

並列摘要

This investigation of doping yttrium oxide and niobium oxide to bismuth oxide based electrolyte makes the fluorite structure stable in room temperature, so as to get the solid electrolyte which exhibits good properties. The aim of this research is to develop the intermediate temperature type solid state oxide fuel cell, the lower operating temperature than the commercialized electrolyte-YSZ at present, and to reduce the cost. Without doping aliovalent ions, bismuth based electrolyte belong to the defect fluorite structure, with an attribute of having 25% vacancies in itself, a kind of defect fluorite structure, the bismuth oxide has good ionic conductivity.
By doping yttrium oxide and niobium oxide to the Bi1-xYxO1.5 (x = 0.20~0.30) and Bi1-yNbyO1.5+δ (y = 0.15~0.25), sintering at 800~950oC, then we are able to observe how properties are influenced at temperature variation. We also analyze the properties and features of structure at several conditions by XRD, SEM, Raman, TEM, DC impedance, EIS, CTE etc. After sintering we identify the specimens as the fluorite structure (Fm‾("3" )m) by XRD, then use SEM to observe the specimen, the grains grow and became more compacted as the sintering temperature rises. In YSB system, the average grain size is 0.59 μm at 30YSB/800oC, 10.63 μm at 20YSB/950oC.While in NDB system, the grain is larger than that in YSB system, the average grain size is 0.49 μm at 25NDB/850oC, 29.35 μm at 15NDB/950oC. In Raman spectroscopy analysis, we find the characteristic peak appears at wavenumber 110.7 cm-1 and 617.3 cm-1 in YSB system, in NDB system, the peaks appear at the anterior wavenumber 96 cm-1, 145 cm-1, and 740.6 cm-1 at the posterior. According to aforesaid data, we confirm that the later is the cubic-type structure. 20YSB/950oC showed the highest ionic conductivity in this DC-impedance experiment; and the conductivity of 20YSB/800oC is 0.75 S/cm and 20YSB/950oC is 1.97 S/cm at 800oC in YSB system, respectively. 15NDB/800oC shows 0.38 S/cm and 15NDB/950oC slightly up to 0.41 S/cm at 800oC in NDB system, respectively. Through EIS experiment, we are able to observe that the resistance is decreased while the estimate temperature rises up both in YSB and NDB system. In TEM microscopic analysis, we catch sight of different extra diffraction patterns by using the select area diffraction, and observe two structures– type II and type III co-exist in 25NDB/950oC specimen from high-resolution image. Examination of physical property on coefficient of thermal expansion showed that 20YSB/800oC is 22.6×10-6/oC, 30YSB/800oC is 20.6×10-6/oC, 15NDB/800oC is 19.5×10-6/oC at 600oC, respectively.

並列關鍵字

Solid Oxide Fuel Cell ； Solid electrolyte ； Bismuth oxide ； Defect fluorite structure

參考文獻

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