大氣電漿熔射製備中溫型固態電解質Sc2O3-Y2O3-ZrO2及其特性分析

Preparation and Characterization of Solid Electrolyte for IT-SOFC using Atmospheric Plasma Spray

康朝翔(Chao-Hsiang Kang)

指導教授 ： 童國倫

中原大學/工學院/化學工程研究所/碩士(2009年)

https://doi.org/10.6840/cycu200901267

摘要

本研究利用大氣電漿熔射系統製備固態氧化物燃料電池電解質層，並探討不同組成的添加劑對其氧離子導電度之影響，用以獲得高效率的燃料電池。
研究結果發現，大氣電漿熔射技術可提供極高的火焰溫度，用以快速的形成穩定的塗層與晶型結構，並減少傳統燒結製程上所耗費的時間與能量。在粉體的製備方面，晶型的強度比例可藉由提高鍛燒溫度來改善添加劑的混掺效果，將鍛燒溫度提升至 1400 ℃後，添加比例濃度有明顯改善。另外，在電解質的製備方面，由 XRD 分析指出，波峰角度的偏移與添加劑濃度有明顯的關係，經由計算結果顯示，以 9-ScYZ 較接近 9 mol% ScSZ 的添加劑濃度，所以擁有較好的立方晶型結構，並有利於氧離子傳導。而 0-ScYZ 與 5-ScYZ 除了添加劑濃度不足外，所形成的多晶相結構亦是造成導電值下降的原因。從 SEM 觀察電解質表面及截面的堆疊情形可以發現，通常會產生長型的裂紋孔洞，而造成孔隙度增加。在阻抗量測方面，以未添加 Sc2O3 電解質的阻抗值最大，且阻抗值隨添加 Sc2O3 比例增加而減少。另外，由阻抗所得到的半圓弧直徑大小可得知電荷轉移阻抗值大小，結果顯示，以未添加 Sc2O3 電解質的電極與電解質間的電荷轉移阻抗值較大。改變操作溫度後，離子導電度隨溫度增加而增加，以 9-ScYZ 上升幅度最高。
綜合上述結果，得知利用 APS 可以大幅度的減少傳統燒結上所耗費的時間與能量。但粉體的製備與熔射參數的設定為影響電解質效能好壞的主要因素，因為粉體混合是否均勻，影響到隨後晶相結構的穩定程度，另外，熔射參數的設定與孔隙度有著相當大的關係，若能將孔隙度降至 5 % 以下，則可以減少離子傳遞的阻抗值大小，最後製備一高傳導的電解質。

關鍵字

大氣電漿熔射 ； 固態電解質 ； 氧化鋯 ； 離子導電度 ； 中溫型固態氧化物燃料電池

並列摘要

In this study, the electrolyte of solid oxide fuel cell (SOFC) was prepared by atmospheric plasma spray system (APS) to investigate the effect of material compositions on ionic conductivity for developing high efficiency SOFC.
The results showed that the APS can provide high torch temperature to rapidly stabilize the cubic phase. In addition, this process was proved to successfully reduce the preparative time and energy consuming. Regarding the preparation of powders, it was found that the cubic phase ratio could be increased by raising the annealing temperature. The doping efficiency can also be obviously improved by annealing at 1400 ℃. On the other hand, the XRD patterns can also indicate the relationship between two theta degree value and dopant concentration in the prepared electrolytes. The calculated value revealed that the dopant concentration of 9-ScYZ more approached the real dopant concentration compared with the other two electrolytes. This suggested that the crystal structure could get more stable cubic phase and then facilitate the increase of ionic conductivity. Otherwise, it was found that the calculated values of 0-ScYZ and 5-ScYZ were smaller than the real dopant concentration. In the SEM images, it was clearly observed that the surface and cross-section of electrolytes produced many cracks, which were also one of the factors to increase the porosity. In the resistance analysis part, it was found that the Y2O3-riched solid electrolyte revealed a higher ohmic resistance compared with the other two solid electrolytes doped with Sc2O3. Moreover, the ohmic resistance decreased as an increase of Sc2O3. Meanwhile, the semicircle diameter of Nyquist plot also indicated the charge transfer resistance. The results showed that the Y2O3-riched solid electrolyte has highest charge transfer resistance at the electrolyte/electrode interface. The ionic conductivity significantly increased when operating temperature increased.
In conclusion, the APS system effectively reduced the preparation time and the resource consumption. The higher electrolyte performance depends on the uniform powders and optimum parameters. The stable cubic phase is determined by the uniform powders. Furthermore, the optimum parameters have significant relationship with porosity. The resistance of ionic conductivity would be reduced if the porosity can be lower than 5 vol. % and then preparing highly conductivity electrolyte.

並列關鍵字

IT-SOFC ； Ionic conductivity ； Zirconia-based ； Solid Electrolyte ； APS

參考文獻

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