| Description |
The focus of this dissertation is to obtain an atomic-level understanding of the effects of doping-induced defects in materials used for solid oxide fuel cells (SOFCs), based on first-principles density functional theory (DFT) calculations. To improve the SOFC performance, doping technique is commonly adopted to introduce external defects, such as creating extra oxygen vacancies to speed up the ion conducting rate. Much experimental effort has been made to gain important fundamental understanding of defect properties in the SOFC materials, especially at the macroscopic level. On the other hand, computational studies can be useful to give microscopic views of defects at the atomic level, which are usually difficult to acquire from experiments. These computational studies can not only help explain experimental results, but also make predictive suggestions for new experiments. Based on first-principles DFT calculations, we have carried out a focused study of the effects of doping-induced defects in some SOFC related materials. Specifically, this dissertation includes three topics of studies: (1) defect configuration and phase stability of cubic vs. tetragonal yttria-stabilized zirconia; (2) suppression of Sr surface segregation in La1-xSrxCo1-yFeyO3-δ; (3) understanding cation ordering and oxygen vacancy site preference in Ba3CaNb2O9. Overall, my dissertation demonstrates that DFT can be employed to aid our fundamental understanding of the effects of doping-induced defects on some key material properties governing the efficiency of SOFCs, and hence to benefit to the development of better SOFC materials. |
