Cation Exchange as a Mechanism To Engineer Polarity in Layered Perovskites
Cation Exchange as a Mechanism To Engineer Polarity in Layered Perovskites
复制标题
DOI：
10.1021/acs.chemmater.8b04136
复制
发表时间：
2018-11
影响因子：
8.6
通讯作者：
Tong Zhu;G. Khalsa;Dana Havas;A. Gibbs;Weiguo Zhang;P. Halasyamani;N. Benedek;M. Hayward
中科院分区：
文献类型：
--
作者：
Tong Zhu;G. Khalsa;Dana Havas;A. Gibbs;Weiguo Zhang;P. Halasyamani;N. Benedek;M. Hayward
使用LiNO 3和NaNO 3对n = 2的Dion-Jacobson相RbNdNb 2 O 7和RbNdTa 2 O 7进行阳离子交换反应，得到相应的LiNdM 2 O 7和NaNdM 2 O 7（M = Nb，Ta）相。同步辐射X射线和中子粉末衍射数据，结合二次谐波产生数据和第一性原理密度泛函计算，揭示了LiNdM 2 O 7相采用n = 2 Ruddlesden-Popper型结构，具有a-a-c+/-（a-a-c+）畸变，空间群为B2cm。相比之下，NaNdM 2 O 7相采用中心对称空间群P42/mnm中描述的具有a-b 0 c 0/b 0a-c 0畸变的n = 2 Ruddlesden-Popper型结构。LiNdM_2O_7和NaNdM_2O_7相的不同结构是基于（i）通过八面体倾斜优化Li/Na配位点的大小和（ii）在（Li/Na）O_2片层内有序化Na/Li阳离子以最小化阳离子-阳离子排斥之间的竞争而合理化的。
Cation-exchange reactions performed on the n = 2 Dion–Jacobson phases RbNdNb2O7 and RbNdTa2O7, using LiNO3 and NaNO3, yield the corresponding LiNdM2O7 and NaNdM2O7 (M = Nb, Ta) phases. Synchrotron X-ray and neutron powder diffraction data, in combination with second-harmonic generation data and supported by first-principles DFT calculations, reveal that the LiNdM2O7 phases adopt n = 2 Ruddlesden–Popper type structures with an a–a–c+/–(a–a–c+) distortion described in the polar space group B2cm. In contrast, the NaNdM2O7 phases adopt n = 2 Ruddlesden–Popper type structures with an a–b0c0/b0a–c0 distortion, described in the centrosymmetric space group P42/mnm. The differing structures adopted by the LiNdM2O7 and NaNdM2O7 phases are rationalized on the basis of a competition between (i) optimizing the size of the Li/Na coordination site via octahedral tilting and (ii) ordering the Na/Li cations within the (Li/Na)O2 sheets to minimize cation–cation repulsion—the former appears to be the dominant factor for the...