Department of Chemistry, School of Science, The University of Tokyo , 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan.
Department of Chemistry, Graduate School of Science, Tohoku University , 6-3 Aramaki Aza Aoba, Aoba, Sendai, Miyagi 980-8578, Japan.
ACS Nano. 2017 Apr 25;11(4):3860-3866. doi: 10.1021/acsnano.7b00144. Epub 2017 Mar 28.
Mixed-anion perovskites such as oxynitrides, oxyfluorides, and oxyhydrides have flexibility in their anion arrangements, which potentially enables functional material design based on coordination chemistry. However, difficulty in the control of the anion arrangement has prevented the realization of this concept. In this study, we demonstrate strain engineering of the anion arrangement in epitaxial thin films of the CaSrTaON perovskite oxynitrides. Under compressive epitaxial strain, the axial sites in TaON octahedra tend to be occupied by nitrogen rather than oxygen, which was revealed by N and O K-edge linearly polarized X-ray absorption near-edge structure (LP-XANES) and scanning transmission electron microscopy combined with electron energy loss spectroscopy. Furthermore, detailed analysis of the LP-XANES indicated that the high occupancy of nitrogen at the axial sites is due to the partial formation of a metastable trans-type anion configuration. These results are expected to serve as a guide for the material design of mixed-anion compounds based on their anion arrangements.
混合阴离子钙钛矿，如氮氧化物、氟氧化物和氢氧化物，在阴离子排列上具有灵活性，这可能使基于配位化学的功能材料设计成为可能。然而，阴离子排列的控制困难阻碍了这一概念的实现。在这项研究中，我们证明了外延薄膜中钙钛矿型氮氧化物的阴离子排列的应变工程。在压缩外延应变下，TaON 八面体的轴向位置倾向于被氮而不是氧占据，这一点通过 N 和 O K 边线性偏振 X 射线吸收近边结构 (LP-XANES) 和电子能量损失光谱结合扫描透射电子显微镜揭示出来。此外，对 LP-XANES 的详细分析表明，轴向位置高氮占有率是由于部分形成了亚稳态的反式阴离子构型。这些结果有望为基于阴离子排列的混合阴离子化合物的材料设计提供指导。
