ChemInform Abstract: Structural Investigations on the Oxidenitrides SrTaO2N, CaTaO2N, and LaTaON2 by Neutron and X‐Ray Powder Diffraction.

Günther, E.; Hagenmayer, R. M.; Jansen, Martin

doi:10.1002/chin.200046002

Cited by 9 publications

(15 citation statements)

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“…For example, in perovskite oxynitrides, the N 2p orbital strongly prefers local cis coordination, in which the orbital overlap between N 2p and empty d orbitals is maximized . In addition, the local cis -unit tends to align with random orientation over a long-range due to the similar bond lengths of metal–nitrogen and metal–oxygen bonds. , For example, in the case of SrTaO 2 N, cis -type local geometry is thermodynamically more stable than the trans -type, − and the long-range arrangement of cis units is completely random or only partially ordered. , The trans -type configuration was reported only in ref , in which the refinement of the neutron diffraction data may be incomplete, as suggested in ref .…”

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confidence: 99%

Strain Engineering for Anion Arrangement in Perovskite Oxynitrides

et al. 2017

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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.

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Strain Engineering for Anion Arrangement in Perovskite Oxynitrides

et al. 2017

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“…Solar hydrogen generation through water splitting is a promising strategy for obtaining clean and renewable energy sources. − For the effective use of this technique, the band gaps of the photocatalysts employed should be limited to 1.7–2.4 eV to achieve more than 10% solar-to-hydrogen (STH) efficiency. − (Oxy)Nitrides are promising candidate materials because they have appropriate band structures for solar water splitting. − …”

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confidence: 99%

Oxygen-Impurity-Induced Direct–Indirect Band Gap in Perovskite SrTaO₂N

et al. 2017

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Oxynitride semiconductors are considered to be promising candidates for solar water splitting. In this work, we show that oxygen-rich SrTaO 2 N has a band gap with direct−indirect character through twin valence-band maximums (VBMs), resulting in good photoelectronic responses. Compared with the direct band gap of ideal SrTaO 2 N, the additional indirect VBM of the oxygen-rich solid solution was found to be due to strontium−oxygen hybridization, using orbital projections based on hybrid/GW density functional theory (DFT). This twin-VBM character was validated by strontium K-edge absorption through extended X-ray absorption fine structure (EXAFS) analysis. The twin-VBM character of the band structure can enhance the photoelectronic response and hole transport. Our findings provide a viable strategy for enhancing the solar water splitting performance of oxynitrides.Article pubs.acs.org/JPCC

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“…Because CaTaO 2 N already has intrinsic octahedral-tilting of TaO 4 N 2 , that of MgTaO 2 N was successfully modeled by imposing the former coordinates as the initial ones for the latter structure. In addition, because many experimental observations for N orderings in perovskite oxynitrides have shown that O/N arrangements in perovskite crystals are not fully random, − we decided to directly model the possible anion arrangements instead of applying special quasirandom structure (SQS) where the anions are assumed to be distributed randomly . In particular, we prepared 13 different anion orderings (hereafter also aors ), from A1 to F4 as shown in Figure S1 in the Supporting Information, similarly to our previous analysis on the aors of CaTaO 2 N …”

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confidence: 99%

MgTaO₂N Photocatalysts: Perovskite versus Ilmenite Structure. A Theoretical Investigation

2017

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We discuss the applicability of magnesium tantalum oxynitride (in the ABO2N stoichiometry) as photocatalyst by calculating its fundamental properties from first principles, fully analyzing structural factors and material polymorphism. We find that, because of their favorable band edge nature, most of the configurations of the perovskite-type MgTaO2N are suitable for water splitting, while ilmenite-type MgTaO2N, the structurally expected more favored polymorph here investigated, is mostly unsuitable for the overall water splitting. Our results also show the strong correlation between the conduction band structures and octahedral tilting, i.e., the more tilted the octahedra, the larger the overlap between Ta 5d bands and anion 2p bands, with subsequent band gap opening and dispersion reduction. Therefore, in the perovskite-type MgTaO2N material design for photocatalytic applications, reduced (if not totally suppressed) octahedral tilting (i.e., via A-site doping) is highly desirable in order to improve the solar-to-energy performance of the material.

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ChemInform Abstract: Structural Investigations on the Oxidenitrides SrTaO₂N, CaTaO₂N, and LaTaON₂ by Neutron and X‐Ray Powder Diffraction.

Cited by 9 publications

References 1 publication

Strain Engineering for Anion Arrangement in Perovskite Oxynitrides

Strain Engineering for Anion Arrangement in Perovskite Oxynitrides

Oxygen-Impurity-Induced Direct–Indirect Band Gap in Perovskite SrTaO₂N

MgTaO₂N Photocatalysts: Perovskite versus Ilmenite Structure. A Theoretical Investigation

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ChemInform Abstract: Structural Investigations on the Oxidenitrides SrTaO2N, CaTaO2N, and LaTaON2 by Neutron and X‐Ray Powder Diffraction.

Cited by 9 publications

References 1 publication

Strain Engineering for Anion Arrangement in Perovskite Oxynitrides

Strain Engineering for Anion Arrangement in Perovskite Oxynitrides

Oxygen-Impurity-Induced Direct–Indirect Band Gap in Perovskite SrTaO2N

MgTaO2N Photocatalysts: Perovskite versus Ilmenite Structure. A Theoretical Investigation

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ChemInform Abstract: Structural Investigations on the Oxidenitrides SrTaO₂N, CaTaO₂N, and LaTaON₂ by Neutron and X‐Ray Powder Diffraction.

Oxygen-Impurity-Induced Direct–Indirect Band Gap in Perovskite SrTaO₂N

MgTaO₂N Photocatalysts: Perovskite versus Ilmenite Structure. A Theoretical Investigation