Potential of pyrochlore structure materials in solid oxide fuel cell applications

Anantharaman, Anjana P.; Dasari, Hari Prasad

doi:10.1016/j.ceramint.2020.10.012

Cited by 102 publications

(48 citation statements)

References 117 publications

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“…19 In general, Ta-containing compositions 8 , 17 , 18 , 20 − 23 possess lower dielectric permittivity compared to the bismuth niobate-based analogues. 24 − 32 …”

Section: Introductionmentioning

confidence: 99%

Novel Ni-Doped Bismuth–Magnesium Tantalate Pyrochlores: Structural and Electrical Properties, Thermal Expansion, X-ray Photoelectron Spectroscopy, and Near-Edge X-ray Absorption Fine Structure Spectra

et al. 2021

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The samples of Ni-doped bismuth magnesium tantalate pyrochlores with the general formula Bi 1.4 (Mg 1– x Ni x ) 0.7 Ta 1.4 O 6.3 ( x = 0.3, 0.5, 0.7) were obtained by solid-phase synthesis. The crystal structure of the pyrochlore type (sp. gr. Fd 3̅ m:2 ) was clarified by the Rietveld method on the basis of X-ray powder diffraction data. The unit cell parameters increase with the decreasing nickel content in the range from 10.5319(1) to 10.5391(1) Å. The electronic state of atoms is established by the XPS method. According to XPS analysis, bismuth atoms have an effective charge of +3, nickel atoms +(2 + δ), and tantalum ions +(5 – δ). The coefficient of thermal expansion of the lattice of the samples was calculated from high-temperature X-ray structural measurements in the range of −180 to 1050 °C. The average values of linear TECs α in the temperature ranges of 30–570 and 600–1050 °C are 5.1 × 10 –6 and 8.1 × 10 –6 °C –1 , respectively. The monotonicity of the change in the thermal expansion coefficient in the temperature range from −100 to 1050 °C indicates the absence of phase transformations. All samples are dielectric and exhibit high activation energies ∼2.0 eV, moderately high dielectric constants ∼24–28, and tangent dielectric losses ∼0.002 at 1 MHz and 21 °C. The electrical properties of the samples are described by a simple parallel equivalent scheme. The chemical composition of the materials has little effect on the polarizability of the medium or on the value of the activation energy of the conductivity. Ionic processes in investigated materials at frequencies 200–10 6 Hz and at temperatures 100–450 °C were not detected.

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“…19 In general, Ta-containing compositions 8 , 17 , 18 , 20 − 23 possess lower dielectric permittivity compared to the bismuth niobate-based analogues. 24 − 32 …”

Section: Introductionmentioning

confidence: 99%

Novel Ni-Doped Bismuth–Magnesium Tantalate Pyrochlores: Structural and Electrical Properties, Thermal Expansion, X-ray Photoelectron Spectroscopy, and Near-Edge X-ray Absorption Fine Structure Spectra

et al. 2021

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“…This fact can be explained during consideration of the ionic radii of Ti and the dopants. The R ion values of the Sc 3+ (0.745 Å) and In 3+ (0.8 Å) ions are slightly larger than Ti 4+ (0.605 Å) at sixfold coordination but acceptable to maintain the tolerance of the pyrochlore structure 47 . Thus, the dopants (Sc or In) can also be located at the sixfold octahedral coordination of the pyrochlore structure ( B ‐site).…”

Section: Resultsmentioning

confidence: 99%

Low‐temperature dielectric behavior of Sc‐ and In‐doped bismuth titanate pyrochlores

2021

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The detailed structural description and analysis of dielectric behavior of Bi1.6MxTi2O7‐δ (M – Sc, In; x = 0.2, 0.4, 0.6) compositions are demonstrated. Doping results in cation disorder either in A‐site (x = 0.2, 0.4) or A‐,B‐sites (x = 0.6) of pyrochlore. The displacements of the A‐site atoms and O′ from the ideal sites are shown. For both dopants, the maximum dielectric constant ε′ was 98, and the dielectric losses remain reasonably close to the values below 0.0058 at x = 0.4, 25 °C, 1 MHz. A drop of ε′ is observed at the other dopants concentrations. With the dopant content rising, the temperature coefficient of capacitance (TCC) increases and is positive (579 ÷ 782 ppm/°C) below room temperature (RT) and then becomes negative (−49 ÷ −220 ppm/°C) above RT. The revealed low‐temperature relaxation process could be associated with jumps of the A‐ions within the A2O′ substructure.

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“…A 2 B 2 O 7 -type pyrochlore materials have shown tremendous potential in this direction as multifunctional materials for a variety of applications, particularly defect-induced photo/radioluminescence, catalysis, solid oxide fuel cells, and as a nuclear waste host. [7][8][9] Globally, there has been a gradual upsurge in research pertaining to defect-and dopant-induced luminescence in oxide lattices. However, a clear understanding of the origin of defect-and dopantinduced luminescence is still missing.…”

Section: Introductionmentioning

confidence: 99%

Bright aspects of defects and dark traits of dopants in the photoluminescence of Er₂X₂O₇:Eu³⁺ (X = Ti and Zr) pyrochlore: an insight using EXAFS, positron annihilation and DFT

et al. 2021

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Potential of pyrochlore structure materials in solid oxide fuel cell applications

Cited by 102 publications

References 117 publications

Novel Ni-Doped Bismuth–Magnesium Tantalate Pyrochlores: Structural and Electrical Properties, Thermal Expansion, X-ray Photoelectron Spectroscopy, and Near-Edge X-ray Absorption Fine Structure Spectra

Novel Ni-Doped Bismuth–Magnesium Tantalate Pyrochlores: Structural and Electrical Properties, Thermal Expansion, X-ray Photoelectron Spectroscopy, and Near-Edge X-ray Absorption Fine Structure Spectra

Low‐temperature dielectric behavior of Sc‐ and In‐doped bismuth titanate pyrochlores

Bright aspects of defects and dark traits of dopants in the photoluminescence of Er₂X₂O₇:Eu³⁺ (X = Ti and Zr) pyrochlore: an insight using EXAFS, positron annihilation and DFT

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Potential of pyrochlore structure materials in solid oxide fuel cell applications

Cited by 102 publications

References 117 publications

Novel Ni-Doped Bismuth–Magnesium Tantalate Pyrochlores: Structural and Electrical Properties, Thermal Expansion, X-ray Photoelectron Spectroscopy, and Near-Edge X-ray Absorption Fine Structure Spectra

Novel Ni-Doped Bismuth–Magnesium Tantalate Pyrochlores: Structural and Electrical Properties, Thermal Expansion, X-ray Photoelectron Spectroscopy, and Near-Edge X-ray Absorption Fine Structure Spectra

Low‐temperature dielectric behavior of Sc‐ and In‐doped bismuth titanate pyrochlores

Bright aspects of defects and dark traits of dopants in the photoluminescence of Er2X2O7:Eu3+ (X = Ti and Zr) pyrochlore: an insight using EXAFS, positron annihilation and DFT

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Bright aspects of defects and dark traits of dopants in the photoluminescence of Er₂X₂O₇:Eu³⁺ (X = Ti and Zr) pyrochlore: an insight using EXAFS, positron annihilation and DFT