Polar nano-region structure in the oxynitride perovskite LaTiO<sub>2</sub>N

Yamaura, Jun‐ichi; Maki, Sachiko; Honda, Toshio; Matsui, Y.; Noviyanto, Alfian; Otomo, Toshiya; Abe, Hitoshi; Murakami, Youichi; Ohashi, Naoki

doi:10.1039/c9cc07029j

Cited by 9 publications

(6 citation statements)

References 38 publications

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“…This is similar to the findings by Fry and Woodward and provides a new avenue to explore in designing hybrid improper polar materials . The displacive disorder of the anion sites observed in bulk ceramic samples (here and Needs et al) is likely to disrupt tendencies for O 2– /F – ordering over the anion sites, but the possibility of local regions that are non-centrosymmetric (similar to recent reports in oxynitrides) has potential for the design of new materials with relaxor-like properties . Our use of the Rietveld method combined with bond valence penalties , can give additional chemical information for the structural analysis of systems with atoms of similar scattering lengths.…”

Section: Discussionsupporting

confidence: 79%

“…However, this preference rarely gives long-range N 3– /O 2– order, and instead, a correlated order (comprising cis- anion chains) emerges . This lack of long-range site order is thought to disrupt long-range correlations between any polar displacement in the oxynitrides, , limiting the length scale of any polar region and can give polar nanoregions …”

Section: Discussionmentioning

confidence: 99%

“…74 This lack of long-range site order is thought to disrupt long-range correlations between any polar displacement in the oxynitrides, 75,76 limiting the length scale of any polar region and can give polar nanoregions. 77 4.3. Polar Structures from Nonpolar Anion Order and Nonpolar Tilts.…”

Section: Discussionmentioning

confidence: 99%

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Symmetry and the Role of the Anion Sublattice in Aurivillius Oxyfluoride Bi₂TiO₄F₂

et al. 2021

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The photocatalytic and dielectric behaviors of Aurivillius oxyfluorides such as Bi 2 TiO 4 F 2 depend sensitively on their crystal structure and symmetry but these are not fully understood. Our experimental work combined with symmetry analysis demonstrates the factors that influence anion order and how this might be tuned to break inversion symmetry. We explore an experimental approach to explore anion order, which combines Rietveld analysis with strain analysis.

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Section: Discussionsupporting

confidence: 79%

Section: Discussionmentioning

confidence: 99%

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Symmetry and the Role of the Anion Sublattice in Aurivillius Oxyfluoride Bi₂TiO₄F₂

et al. 2021

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“…In pseudocubic perovskites all anion sites show similar coordination environments with cations, favouring total disorder of nitrogen and oxygen or partial order with local cis configuration of B −N bonds . The origin of ferroelectricity in tantalum and titanium perovskite oxynitrides is still under discussion, and large dielectric polarizability is ascribed to the presence of randomly oriented local dipoles induced by the cis order of nitrides in the B O 4 N 2 octahedra …”

Section: Figurementioning

confidence: 99%

Engineering Polar Oxynitrides: Hexagonal Perovskite BaWON₂

et al. 2020

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Non‐centrosymmetric polar compounds have important technological properties. Reported perovskite oxynitrides show centrosymmetric structures, and for some of them high permittivities have been observed and ascribed to local dipoles induced by partial order of nitride and oxide. Reported here is the first hexagonal perovskite oxynitride BaWON2, which shows a polar 6H polytype. Synchrotron X‐ray and neutron powder diffraction, and annular bright‐field in scanning transmission electron microscopy indicate that it crystalizes in the non‐centrosymmetric space group P63mc, with a total order of nitride and oxide at two distinct coordination environments in cubic and hexagonal packed BaX3 layers. A synergetic second‐order Jahn–Teller effect, supported by first principle calculations, anion order, and electrostatic repulsions between W6+ cations, induce large distortions at two inequivalent face‐sharing octahedra that lead to long‐range ordered dipoles and spontaneous polarization along the c axis. The new oxynitride is a semiconductor with a band gap of 1.1 eV and a large permittivity.

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“…The perovskite-type oxynitride, LaTiO 2 N, is an orthorhombic structure belonging to the Imma space group in which O and N atoms occupy random anion sites. Yamaura et al investigated the local structure of LaTiO 2 N using the extended X-ray absorption fine structure (EXAFS) and neutron pair distribution function (PDF) techniques . These analyses revealed that the local structure at short-range scales of r < 8 Å is polar, although the average structure is centrosymmetric.…”

Section: Introductionmentioning

confidence: 99%

Existence of Local Polar Domains in Perovskite Oxyfluoride, BaFeO₂F

Katsumata,

Suzuki,

Satoh

et al. 2024

Chem. Mater.

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We prepared high-purity Sr 1−x Ba x FeO 2 F by a lowtemperature fluorination method, investigated the average structure by synchrotron X-ray diffraction (SXRD), and measured second harmonic generation (SHG) in this material. For BaFeO 2 F, the average and local structures were investigated by time-of-flight (TOF) neutron diffraction and the X-ray pair distribution function (PDF), respectively. In addition, the magnetic moment under a magnetic field was measured. SHG was observed for Sr 1−x Ba x FeO 2 F (x = 1.0, 0.9, and 0.7) and was below the detection limit for x = 0.5. The average crystal structure of BaFeO 2 F was determined by the refinement of the TOF neutron diffraction data to be a cubic structure in which Fe 3+ ions are displaced to (x, x, 1/2) off-site positions with a 1/12 occupancy. The magnetic structure was a G-type antiferromagnetic structure, and the magnetic moments of the Fe 3+ ion were 3.84 and 3.50 μ B at 3 and 300 K, respectively. According to the X-ray PDF analysis, the local structure was not a cubic structure with the equivalent displacement of the Fe 3+ ion to the off-site positions but a noncentrosymmetric structure in which Fe 3+ ions are displaced in various directions in distorted BX 6 octahedra. These local polar domains induce the SHG. The coexistence of polar domains with different polarization directions results in a cubic average structure. The formation of local polar domains was supported by the canted ferromagnetic components observed in magnetic moment measurements carried out under an applied magnetic field.

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Polar nano-region structure in the oxynitride perovskite LaTiO₂N

Abstract: Polar nano-region formation in the oxynitride perovskite LaTiO2N is demonstrated from PDF analysis.

Cited by 9 publications

References 38 publications

Symmetry and the Role of the Anion Sublattice in Aurivillius Oxyfluoride Bi₂TiO₄F₂

Symmetry and the Role of the Anion Sublattice in Aurivillius Oxyfluoride Bi₂TiO₄F₂

Engineering Polar Oxynitrides: Hexagonal Perovskite BaWON₂

Existence of Local Polar Domains in Perovskite Oxyfluoride, BaFeO₂F

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Polar nano-region structure in the oxynitride perovskite LaTiO2N

Abstract: Polar nano-region formation in the oxynitride perovskite LaTiO2N is demonstrated from PDF analysis.

Cited by 9 publications

References 38 publications

Symmetry and the Role of the Anion Sublattice in Aurivillius Oxyfluoride Bi2TiO4F2

Symmetry and the Role of the Anion Sublattice in Aurivillius Oxyfluoride Bi2TiO4F2

Engineering Polar Oxynitrides: Hexagonal Perovskite BaWON2

Existence of Local Polar Domains in Perovskite Oxyfluoride, BaFeO2F

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Polar nano-region structure in the oxynitride perovskite LaTiO₂N

Symmetry and the Role of the Anion Sublattice in Aurivillius Oxyfluoride Bi₂TiO₄F₂

Symmetry and the Role of the Anion Sublattice in Aurivillius Oxyfluoride Bi₂TiO₄F₂

Engineering Polar Oxynitrides: Hexagonal Perovskite BaWON₂

Existence of Local Polar Domains in Perovskite Oxyfluoride, BaFeO₂F