Oxygen-deficiency-induced 6H-polymorph of hexagonal perovskite Ba4YMn3O11.5−δ: synthesis, structure and properties

Kuang, Xiaojun; Zhu, Hong; Allix, Mathieu; Bridges, Craig A.; Rosseinsky, Matthew J.; Li, Yuexiang

doi:10.1039/c2jm15845k

Cited by 12 publications

(5 citation statements)

References 24 publications

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“…The electrode response indeed was confirmed by impedance measurements using copper and platinum electrodes at ambient temperature on another pellet, which showed semicircular arcs with different radii but essentially the same high-frequency intercepts (Figure S4). Meanwhile, we chose the CaCu 3 Ti 4 O 12 (CCTO) ceramic as a reference to verify whether the measurement cell influences the impedance data. The CCTO ceramic is a well-known high-dielectric permittivity material consisting of semiconducting grains and an insulating grain boundary region. , Impedance data of CaCu 3 Ti 4 O 12 recorded inside and outside the cryostat (Figure S5) do not show a significant difference in the high-frequency intercept (for the grain resistances) and semicircular arc size (for the grain boundary resistances), thus confirming that the measurement cell makes little contribution to the impedance data.…”

Section: Resultsmentioning

confidence: 66%

Section: ■ Methodsmentioning

confidence: 99%

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High Dielectric Permittivity of α-NaFeO₂-Type Layered Nitrides

Liu

Wang

et al. 2022

Chem. Mater.

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The exploration of new high-dielectric materials is crucial for the advancement of modern electronic applications. Most previous research on high dielectrics has been limited to oxides. Here, the structures of nitrides SrHfN 2 and SrZrN 2 were investigated by neutron powder diffraction, which confirmed their α-NaFeO 2 -type layered structure without showing apparent preferences of octahedral distortion or polar structure. The SrHfN 2 and SrZrN 2 ceramics were found to possess high dielectric permittivities (ε r ) of approximately 290−650 at 10 6 Hz from 5 to 280 K. Impedance spectroscopy measurements indicate the ceramics could contain conducting grains and less conducting grain boundary regions with extremely small activation energies, inducing the internal barrier capacitance effect and therefore extrinsically high dielectric permittivities. Density functional theory calculations indicate that both SrHfN 2 and SrZrN 2 are semiconductors with ∼ 1.0 eV band gaps and possess high bulk ε r values of 280 and 470, respectively. The exceptionally high ε r values of these layered nitrides originate from the anisotropic and large ionic polarization within the a−b plane due to the low-frequency infrared active phonon modes concomitant with a large mode effective charge. Our study not only sheds light on the potential of high-ε r materials but also provides a reference for the study of the dielectric mechanism of layered nitrides.

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Section: Resultsmentioning

confidence: 66%

Section: ■ Methodsmentioning

confidence: 99%

High Dielectric Permittivity of α-NaFeO₂-Type Layered Nitrides

Liu

Wang

et al. 2022

Chem. Mater.

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“…Hexagonal perovskite oxides that are built up from mixed cubic (c) and hexagonal (h) close-packed AO 3 layers have attracted much attention owing to their diverse structural chemistry and technologically important physical properties (e.g., high dielectric permittivity, , oxide ion and proton migration, photocatalytic activities, magnetic order, frustration, , etc.). The various combinations of cubic and hexagonal stacking of AO 3 layers in principle offer a huge possibility of new structural prototypes to be exploited.…”

Section: Introductionmentioning

confidence: 99%

Shift–Twin Option in Eight-Layer Hexagonal Perovskite Niobates Ba₈MNb₆O₂₄

et al. 2020

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Two new eight-layer hexagonal perovskites with the composition Ba8MNb6O24 (M = Fe and Cu) are synthesized by solid-state reaction at 1350–1400 °C. Their crystal structures have been investigated using X-ray and electron diffractions as well as high-resolution transmission electron microscopy. Although both compounds have similar M2+ size, Ba8FeNb6O24 and Ba8CuNb6O24 adopt shifted and twinned structures, respectively. Through comparison with the reported shifted Ba8MNb6O24 (M = Mn, Co, and Zn) and twinned Ba8NiNb6O24 as well as inexistent Ba8Mg(Nb/Ta)6O24, we elucidate that the twin–shift competition of Ba8MNb6O24 family could be related with multiple chemical factors including tolerance factors, B-cationic size difference, entropy variation with B-cation and vacancy disorder, Jahn–Teller distortion, and FSO B–B d orbit interactions.

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“…the Y cations are located in the corner-sharing octahedra, whereas the Mn cations are located in the face-sharing octahedra to form Mn 3 O 12 trimmers. In such hexagonal perovskites, this stacking could change and different polytypes could be found as the oxygen vacancy concentration varies [22,23]. Concerning the ratio of Y 2 O 3 phase, the structure refinement allowed it to be quantified ( Table 1).…”

Section: Resultsmentioning

confidence: 99%