Theoretical analysis on O vacancy and cation inversion in NiCo2O4

• Published in: Materials science & engineering. B, Solid-state materials for advanced technology Solid-state materials for advanced technology, 2021-01, Vol.263, p.114886, Article 114886
• Main Authors: Wu, Chunfang, liu, Lu, Xu, Ruiping, Zhang, Kaiqi, Zhen, Congmian, Ma, Li, Hou, Denglu
• Format: Article
• Language: English
• Subjects: Band structures; Cation inversion; Cations; Density functional theory; Electron states; Electron transitions; Energy levels; Ferrimagnetism; Magnetic moments; Metal ions; Nickel compounds; NiCo2O4; Oxygen vacancy; Spin configuration; Transition metals; Vacancies; Valence band
• ISSN: 0921-5107; 1873-4944
• DOI: 10.1016/j.mseb.2020.114886

•Two typical defects in NCO, O vacancy and cation inversion, were studied.•O vacancy introduces some energy levels, increasing chances of electron hopping.•O vacancy only affects the magnetic moment of the neighbor atoms.•Coordinated sites of metal ions affect their spin state and valence. We have implemented polarized density function theory (DFT) on the transition metal d orbitals to explore the effects of oxygen vacancy and cation inversion on properties of NiCo2O4. The results show that NiCo2O4 has ferrimagnetic half-metallic ground states. Oxygen vacancy introduces additional energy levels in the majority spin band gap, which increases the chance of electron transition. In addition, O vacancy only affects the magnetic moment of the neighbor Oct Ni and Oct Co atoms. Calculations on NiCo2O4 with cation inversion confirms that coordinated sites of metal ions affect their spin state and valence, which further influence the conductivity and ferrimagnetic properties. The valence information of metal ions in NiCo2O4 was given. And the increased electron states in top of valence band make great contributions to p-type conductivity of NiCo2O4.