Jung Dong-Hyuk, Lee Ji-Hwan, Kilic Mehmet Emin, Soon Aloysius
Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Korea.
Phys Chem Chem Phys. 2018 Apr 18;20(15):10048-10059. doi: 10.1039/c8cp00559a.
Ceria doped with Sm and Gd (SDC and GDC) has been suggested as a promising candidate for the electrolyte used in solid oxide fuel cells (SOFCs), since it has relatively high oxygen ion conductivity at intermediate temperature. There have been many previous experimental and computational studies to investigate the properties, structure, and effect of vacancies, etc. for SDC and GDC. However, in these previous studies, it is commonly assumed that the interaction between oxygen vacancies is negligible and many focus only on the mono-vacancy system. In addition, the possibility of anisotropic vibrational motion of the oxygen ions around vacancies is often neglected. In this paper, using both first-principle density-functional theory and classical molecular dynamics calculations, we investigate the structural and vibrational properties of the optimized SDC and GDC structures, such as bonding analysis, phonon density-of-state and mean-square-displacement of the oxygen ions. Also, we report the direction-dependent vibrations at the specific frequency of the oxygen ions near the vacancies, activation energies, and diffusion coefficients of SDC and GDC which can extend our understanding of diffusion dynamics in doped ceria-based electrolytes for SOFC applications.
掺杂钐和钆的二氧化铈（SDC和GDC）被认为是固体氧化物燃料电池（SOFC）中电解质的一个有前途的候选材料，因为它在中温下具有相对较高的氧离子传导率。之前有许多实验和计算研究来探究SDC和GDC的性质、结构以及空位等的影响。然而，在这些先前的研究中，通常假定氧空位之间的相互作用可以忽略不计，并且许多研究仅关注单空位体系。此外，空位周围氧离子各向异性振动的可能性常常被忽视。在本文中，我们使用第一性原理密度泛函理论和经典分子动力学计算，研究了优化后的SDC和GDC结构的结构和振动性质，如键合分析、声子态密度和氧离子的均方位移。此外，我们报告了空位附近氧离子在特定频率下的方向依赖性振动、活化能以及SDC和GDC的扩散系数，这可以扩展我们对用于SOFC应用的掺杂二氧化铈基电解质中扩散动力学的理解。
