Partially Anion-Ordered Cerium Niobium Oxynitride Perovskite Phase with a Small Band Gap

Zonghao Shen; Ji Wu; Matthew W. Shorvon; Guillaume Cazaux; Stephen C. Parker; Stephen J. Skinner

doi:10.1021/acs.chemmater.1c00631

Partially Anion-Ordered Cerium Niobium Oxynitride Perovskite Phase with a Small Band Gap

Zonghao Shen, Ji Wu, Matthew W. Shorvon, Guillaume Cazaux, Stephen C. Parker, Stephen J. Skinner

Imperial College London

Research output: Contribution to journal › Article › peer-review

3 Citations (SciVal)

Abstract

A new phase of black color, cerium niobium oxynitride with general formula CeNb(O,N)3, was synthesized by thermal ammonolysis, and its crystal structure and physical and chemical properties are investigated. Powder X-ray and neutron diffraction has confirmed the perovskite-structured CeNbO1.49(7)N1.51(7) phase crystallized with the orthorhombic Pnma symmetry with unit cell parameters of a = 5.7137(5) Å, b = 8.0567(5) Å, c = 5.7209(5) Å, presenting a partially ordered anionic arrangement. The incorporation of nitrogen into the oxygen sublattice was confirmed by X-ray photoelectron spectroscopy. Complex multistage redox processes of this material at elevated temperatures in air, including full amorphization above 200 °C, recrystallization at 650 °C, decomposition at 950 °C, and a final oxidation into the stoichiometric cerium niobium oxide CeNbO4, were observed by simultaneous thermal analysis and in situ X-ray powder diffraction. The band gap of the oxynitride material was investigated by UV-vis spectroscopy and, due to the incorporation of nitrogen into the oxygen sublattice, a significant decrease from Eg = 2.67 eV for the precursor oxide CeNbO4+δ to Eg = 1.79 eV was observed. The simulation by density functional theory further confirms that the partially ordered anionic arrangement widens the band gap (1.78 eV) and stabilizes the structure compared to the completely ordered (layered) structure (1.22 eV).

Original language	English
Pages (from-to)	4045-4056
Number of pages	12
Journal	Chemistry of Materials
Volume	33
Issue number	11
Early online date	20 May 2021
DOIs	https://doi.org/10.1021/acs.chemmater.1c00631
Publication status	Published - 8 Jun 2021

Funding

J.W. and S.C.P. gratefully acknowledge support from the U.K. Engineering and Physical Sciences Research Council (EP/R023603/1 and EP/P007821/1). J.W and S.C.P. also thank the U.K. ARCHER HPC facility and the THOMAS HPC (the UK Materials and Molecular Modelling Hub, partially funded by EPSRC EP/P020194) for providing computation resources, via our membership of the UK’s HEC Materials Chemistry Consortium (funded by the EPSRC grants: EP/L000202, EP/P007821/1, EP/R029431, EP/T022213). This research has also made use of the Balena High Performance Computing (HPC) Service at the University of Bath. Z.S. and S.J.S. also gratefully acknowledge the GEMXpress facility at the UK Neutron and Muon source (ISIS), Rutherford Appleton Laboratories, funded by the Science and Technology Facilities Council for the award of beam time (XB1370003). Z.S. thanks Dr. Florent Tonus for his assistance with the material synthesis and Dr. Jing Pang and Prof. Mary Ryan for their suggestions with the UV–vis measurements. The authors also thank Dr. Gwilherm Kerherve for assistance with the XPS measurements.

ASJC Scopus subject areas

General Chemistry
General Chemical Engineering
Materials Chemistry

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10.1021/acs.chemmater.1c00631

Cite this

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title = "Partially Anion-Ordered Cerium Niobium Oxynitride Perovskite Phase with a Small Band Gap",

abstract = "A new phase of black color, cerium niobium oxynitride with general formula CeNb(O,N)3, was synthesized by thermal ammonolysis, and its crystal structure and physical and chemical properties are investigated. Powder X-ray and neutron diffraction has confirmed the perovskite-structured CeNbO1.49(7)N1.51(7) phase crystallized with the orthorhombic Pnma symmetry with unit cell parameters of a = 5.7137(5) {\AA}, b = 8.0567(5) {\AA}, c = 5.7209(5) {\AA}, presenting a partially ordered anionic arrangement. The incorporation of nitrogen into the oxygen sublattice was confirmed by X-ray photoelectron spectroscopy. Complex multistage redox processes of this material at elevated temperatures in air, including full amorphization above 200 °C, recrystallization at 650 °C, decomposition at 950 °C, and a final oxidation into the stoichiometric cerium niobium oxide CeNbO4, were observed by simultaneous thermal analysis and in situ X-ray powder diffraction. The band gap of the oxynitride material was investigated by UV-vis spectroscopy and, due to the incorporation of nitrogen into the oxygen sublattice, a significant decrease from Eg = 2.67 eV for the precursor oxide CeNbO4+δ to Eg = 1.79 eV was observed. The simulation by density functional theory further confirms that the partially ordered anionic arrangement widens the band gap (1.78 eV) and stabilizes the structure compared to the completely ordered (layered) structure (1.22 eV).",

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AU - Shen, Zonghao

AU - Wu, Ji

AU - Shorvon, Matthew W.

AU - Cazaux, Guillaume

AU - Parker, Stephen C.

AU - Skinner, Stephen J.

PY - 2021/6/8

Y1 - 2021/6/8

N2 - A new phase of black color, cerium niobium oxynitride with general formula CeNb(O,N)3, was synthesized by thermal ammonolysis, and its crystal structure and physical and chemical properties are investigated. Powder X-ray and neutron diffraction has confirmed the perovskite-structured CeNbO1.49(7)N1.51(7) phase crystallized with the orthorhombic Pnma symmetry with unit cell parameters of a = 5.7137(5) Å, b = 8.0567(5) Å, c = 5.7209(5) Å, presenting a partially ordered anionic arrangement. The incorporation of nitrogen into the oxygen sublattice was confirmed by X-ray photoelectron spectroscopy. Complex multistage redox processes of this material at elevated temperatures in air, including full amorphization above 200 °C, recrystallization at 650 °C, decomposition at 950 °C, and a final oxidation into the stoichiometric cerium niobium oxide CeNbO4, were observed by simultaneous thermal analysis and in situ X-ray powder diffraction. The band gap of the oxynitride material was investigated by UV-vis spectroscopy and, due to the incorporation of nitrogen into the oxygen sublattice, a significant decrease from Eg = 2.67 eV for the precursor oxide CeNbO4+δ to Eg = 1.79 eV was observed. The simulation by density functional theory further confirms that the partially ordered anionic arrangement widens the band gap (1.78 eV) and stabilizes the structure compared to the completely ordered (layered) structure (1.22 eV).

AB - A new phase of black color, cerium niobium oxynitride with general formula CeNb(O,N)3, was synthesized by thermal ammonolysis, and its crystal structure and physical and chemical properties are investigated. Powder X-ray and neutron diffraction has confirmed the perovskite-structured CeNbO1.49(7)N1.51(7) phase crystallized with the orthorhombic Pnma symmetry with unit cell parameters of a = 5.7137(5) Å, b = 8.0567(5) Å, c = 5.7209(5) Å, presenting a partially ordered anionic arrangement. The incorporation of nitrogen into the oxygen sublattice was confirmed by X-ray photoelectron spectroscopy. Complex multistage redox processes of this material at elevated temperatures in air, including full amorphization above 200 °C, recrystallization at 650 °C, decomposition at 950 °C, and a final oxidation into the stoichiometric cerium niobium oxide CeNbO4, were observed by simultaneous thermal analysis and in situ X-ray powder diffraction. The band gap of the oxynitride material was investigated by UV-vis spectroscopy and, due to the incorporation of nitrogen into the oxygen sublattice, a significant decrease from Eg = 2.67 eV for the precursor oxide CeNbO4+δ to Eg = 1.79 eV was observed. The simulation by density functional theory further confirms that the partially ordered anionic arrangement widens the band gap (1.78 eV) and stabilizes the structure compared to the completely ordered (layered) structure (1.22 eV).

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Partially Anion-Ordered Cerium Niobium Oxynitride Perovskite Phase with a Small Band Gap

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Partially Anion-Ordered Cerium Niobium Oxynitride Perovskite Phase with a Small Band Gap

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