Structural Distortion and Dielectric Permittivities of KCoO2-Type Layered Nitrides Ca1- xSr x TiN2

Shenglin Lu; Yanhui Wang; Fengqi Lu; Jie Feng; Kun Lin; Diming Xu; Maxim Avdeev; Laijun Liu; Xiaojun Kuang; Xianran Xing

doi:10.1021/acs.inorgchem.0c00931

Structural Distortion and Dielectric Permittivities of KCoO₂-Type Layered Nitrides Ca_{1- x}Sr _x TiN₂

Inorg Chem. 2020 Jul 20;59(14):9693-9698. doi: 10.1021/acs.inorgchem.0c00931. Epub 2020 Jul 3.

Authors

Shenglin Lu¹, Yanhui Wang¹, Fengqi Lu¹, Jie Feng¹, Kun Lin², Diming Xu³, Maxim Avdeev⁴, Laijun Liu¹, Xiaojun Kuang^{1

5}, Xianran Xing²

Affiliations

¹ MOE Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, Guangxi Key Laboratory of Optical and Electronic Materials and Devices, College of Materials Science and Engineering, Guilin University of Technology, Guilin 541004, P. R. China.
² Beijing Advanced Innovation Center for Materials Genome Engineering and Institute of Solid-State Chemistry, University of Science and Technology Beijing, Beijing 100083, P. R. China.
³ Inorganic Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QR, U.K.
⁴ Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia.
⁵ College of Chemistry and Bioengineering, Guilin University of Technology, Guilin 541004, P. R. China.

PMID: 32618471
DOI: 10.1021/acs.inorgchem.0c00931

Abstract

Among the KCoO₂-type phases, the orthorhombic layered nitride CaTiN₂ is a newly reported high dielectric permittivity material (ε_r ∼ 1300-2500 within 10⁴-10⁶ Hz from 80 to 450 K) while the tetragonal SrTiN₂ is reported to display an unintentional metallic conduction property. In this work, a Ca_1-xSr_xTiN₂ solid solution was synthesized, in which the insulating SrTiN₂ end member and some Sr-doped CaTiN₂ samples were successfully obtained, and therefore, the dielectric properties of the Ca_1-xSr_xTiN₂ solid solution were investigated. The Sr substitution for Ca drove an orthorhombic-to-tetragonal phase transformation in Ca_1-xSr_xTiN₂, which reduced the dielectric permittivity significantly. The tetragonal SrTiN₂ displays a much lower dielectric permittivity (ε_r ∼ 20-70 in 10⁵-10⁶ Hz and 10-300 K) than that of CaTiN₂. The comparison on the dielectric permittivities and structures of CaTiN₂ and SrTiN₂ indicates that the structural distortion arising from the splitting of N planes between Ti layers within the TiN₂ pyramidal layers could be a plausible structural origin of the high bulk dielectric permittivity of CaTiN₂.