Lee Joohwi, Ohba Nobuko, Asahi Ryoji
Toyota Central R&D Laboratories, Inc., Nagakute, Japan.
Sci Technol Adv Mater. 2019 Feb 6;20(1):144-159. doi: 10.1080/14686996.2019.1578183. eCollection 2019.
We systematically investigated trilanthanide gallates (LnGaO) with the space group 2 as oxygen-ion conductors using first-principles calculations. Six LnGaO (Ln = Nd, Gd, Tb, Ho, Dy, or Er) are both energetically and dynamically stable among 15 LnGaO compounds, which is consistent with previous experimental studies reporting successful syntheses of single phases. LaGaO and LuGaO may be metastable despite a slightly higher energy than those of competing reference states, as phonon calculations predict them to be dynamically stable. The formation and the migration barrier energies of an oxygen vacancy ( ) suggest that eight LnGaO (Ln = La, Nd, Gd, Tb, Ho, Dy, Er, or Lu) can act as oxygen-ion conductors based on . Ga plays a role of decreasing the distances between the oxygen sites of LnGaO compared with those of LnO so that a migrates easier with a reduced migration barrier energy. Larger oxygen-ion diffusivities and lower migration barrier energies of for the eight LnGaO are obtained for smaller atomic numbers of Ln having larger radii of Ln. Their oxygen-ion conductivities at 1000 K are predicted to have a similar order of magnitude to that of yttria-stabilized zirconia.
我们使用第一性原理计算系统地研究了空间群为2的三镧系元素镓酸盐（LnGaO）作为氧离子导体的情况。在15种LnGaO化合物中，六种LnGaO（Ln = Nd、Gd、Tb、Ho、Dy或Er）在能量和动力学上都是稳定的，这与之前报道成功合成单相的实验研究一致。尽管LaGaO和LuGaO的能量比竞争参考态略高，但声子计算预测它们是动力学稳定的，因此可能是亚稳的。氧空位（ ）的形成能和迁移势垒能表明，基于 ，八种LnGaO（Ln = La、Nd、Gd、Tb、Ho、Dy、Er或Lu）可以作为氧离子导体。与LnO相比，Ga起到了减小LnGaO中氧位点之间距离的作用，从而使 迁移更容易，迁移势垒能降低。对于半径较大的Ln原子序数较小的八种LnGaO，获得了更大的氧离子扩散率和更低的 迁移势垒能。预测它们在1000 K时的氧离子电导率与氧化钇稳定的氧化锆具有相似的数量级。
