利用電導鬆弛法量測多孔性氧化鈰╱釔安定氧化鋯複合材料之氧離子擴散係數與表面交換常數

Abstract

本實驗試著裡用電導鬆弛法量測多孔性氧化鈰/釔安定氧化鋯複合材料的擴散係數以及表面交換常數。 而為了要能夠製作出良好的多孔性材料，我們將氧化鈰粉末、釔安定氧化鋯粉末以及碳粉進行散佈，並將散佈完成的粉末進行冷壓，接著以高溫爐燒結並以阿基米德法量測其相對密度。而在開始量測試片的性質之前，所有的試片都必須要經過x-ray繞射分析鑑定所產生的結晶相。 從本實驗的結果中，顯示c-Ce2Zr2O7將會影響試片的導電機制。在實驗中產生c-Ce2Zr2O7的試片大多都是不好的離子導體，推測該現象將與c-Ce2Zr2O7所形成的雙氧空孔結構阻礙氧離子的擴散有關。此外，大部分的試片導電度將會隨著氧分壓的增加而增加，然而，含有c-Ce2Zr2O7的試片其導電度卻會隨著氧分壓的增加而減少。 將本實驗結果與實驗室先前的研究”不同組成CeO2/ZrO2 複合材料與鈦金屬高溫擴散反應”做比較，由於受到雙氧空孔的影響，氧離子在c-Ce2Zr2O7 中的擴散速率較慢，將可以有效地抑制鈦金屬與陶瓷的高溫擴散反應。

The target of the research is using conductivity relaxation method to measure the diffusivity and surface exchange coefficient of porous ceria/YSZ composite material in order to find a more suitable material in solid electrolyte. To get a fine porous ceramic composite material, we dispersed the mixture of ceria powder, YSZ powder and carbon powder then cold pressed the powders into a disk of green compact. After sintering in high temperature furnace, we measured the relative densities of the ceramic bulks by Archimedes method. The specimens are analyzed by x-ray diffraction. From the results of the experiments, we could conclude c-Ce2Zr2O7 affects the conduction mechanism of the specimens. Thespecimens which contain c-Ce2Zr2O7 usually are poor ionic conductors. Because the divacancies are formed, the defect would be the barrier for oxygen ion to migrate. Moreover, the conductivity of most of specimens would become lower when the partial pressure of oxygen is reduced, but the specimens contain c-Ce2Zr2O7 would behave in opposite way in some condition.Compared to the result of “Interfacial Phenomenon between III Titanium and Ceria/Zirconia Composites.” , we could find out that the formation of c-Ce2Zr2O7 will restrain the reaction between ceramic and titanium by reduced the mobility of oxygen.