Li- and Mg-codoped bismuth niobate pyrochlores: Synthesis, structure, electrical properties

Королева, М. С.; Пийр, И. В.; Журавлев, Н. А.; Денисова, Т. А.; Истомина, Е. И.

doi:10.1016/j.ssi.2018.12.017

Cited by 12 publications

(36 citation statements)

References 46 publications

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“…Bismuth-based pyrochlores are known to be characterized by the possibility for the displacement of the A-site atoms (from ideal 16c site to 96h or 96g sites) and the oxygen atoms O′ (from 8a site to 32e site). ,,− In this work, the displacement of A-site atoms from 16c site to 96h site caused a better improvement of the fitting parameters for the (Bi 1.38 Cr 0.30 )(Ti 1.84 Cr 0.16 )O 6.44 pyrochlore. Details of the crystal data and selected crystallographic parameters are summarized in Tables and .…”

Section: Resultsmentioning

confidence: 80%

“…The conduction band (CB) formation was produced by the overlapping of the O 2p orbitals with the unoccupied Bi 6p and Ti 3d orbitals. Moreover, spin-polarized states are not typical for Bi 2 Ti 2 O 7 . ,, …”

Section: Resultsmentioning

confidence: 98%

“…Previously we calculated the electronic structure of stoichiometric Bi 2 Ti 2 O 7 . 46 The direct band gap at the X point was found to be 2.65 eV. The valence band (VB) was derived mainly from the Ti 3d and O 2p orbitals with an admixture of the Bi 6s and Bi 6p orbitals (from −5.2 to 0 eV below the Fermi level).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Previously we calculated the electronic structure of stoichiometric Bi 2 Ti 2 O 7 . The direct band gap at the X point was found to be 2.65 eV.…”

Section: Resultsmentioning

confidence: 99%

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Ab Initio and Experimental Insights on Structural, Electronic, Optical, and Magnetic Properties of Cr-Doped Bi₂Ti₂O₇

et al. 2019

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Combined ab initio and experimental study of Cr doping into bismuth titanate pyrochlore was carried out for the first time. Accurate firstprinciples density functional theory calculations were performed considering a Hubbard U correction (DFT+U) to account for on-site Coulomb interactions of the Cr 3d states. The possibility to synthesize a novel pyrochlore-type compound with a high dopant content Bi 1.5 Cr 0.5 Ti 2 O 7 (Bi site doping) in a fine powder state was shown via coprecipitation method, while the single-phase Bi 2 Ti 1.5 Cr 0.5 O 7 (Ti site doping) could not be obtained. Detailed descriptions of thermostability, structural, optoelectronic, and magnetic properties of Cr-doped pyrochlores in the fine (particles size 100− 300 nm) and "bulk" (1−50 μm) powder states are presented based on the well-matched results of theoretical and experimental investigations. According to the Rietveld refinement of the X-ray diffraction data, Bi 1.5 Cr 0.5 Ti 2 O 7 compound is an A-site deficient pyrochlore (Bi 1.38 Cr 0.30 )-(Ti 1.84 Cr 0.16 )O 6.44 with chromium distribution between both cationic sites. Metastability of fine powder Cr-containing pyrochlore phase was revealed during long-thermal annealing, while the bulk powder sample was stable up to its melting point 1230 °C. According to the study of electronic structure and optical properties, Cr-doped pyrochlores are wide-band semiconductors with light absorption in the range of 300−500 nm and perspective as photocatalytic active materials under visible light irradiation. Paramagnetic behavior with effective magnetic moment 3.92 μB (Bi 1.6 Cr 0.1 Ti 2 O 7−δ ) and 3.01 μB (Bi 1.5 Cr 0.5 Ti 2 O 7 ) was experimentally observed. All chromium in magnetically diluted pyrochlore Bi 1.6 Cr 0.1 Ti 2 O 7−δ exists in the form of Cr 3+ monomers, whereas in the more concentrated magnetic Bi 1.5 Cr 0.5 Ti 2 O 7 composition Cr 3+ -O-Cr 3+ dimers may also be present, with a fraction equal to 0.39. This investigation constitutes the first approach to the electronic, structural, optical, and magnetic properties of d-elements doped bismuth titanate pyrochlores from experimental and theoretical viewpoints, emphasizing the power of DFT+U to provide insights and to complement the experimental characterization of these new compounds.

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Section: Resultsmentioning

confidence: 80%

Section: Resultsmentioning

confidence: 98%

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Previously we calculated the electronic structure of stoichiometric Bi 2 Ti 2 O 7 . The direct band gap at the X point was found to be 2.65 eV.…”

Section: Resultsmentioning

confidence: 99%

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Ab Initio and Experimental Insights on Structural, Electronic, Optical, and Magnetic Properties of Cr-Doped Bi₂Ti₂O₇

et al. 2019

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“…These high activation energies could be related to the hopping electronic transport mechanism, which may be due to atomic defects, e.g. existence of the intrinsic oxygen vacancies [15,39,40]. Meanwhile, no distinct trend in the variation of electrical conductivity can be identified with increasing Fe content.…”

Section: Impedance Spectroscopymentioning

confidence: 98%

Investigation of structural and dielectric properties of subsolidus bismuth iron niobate pyrochlores

Jusoh

Tan

Zainal

et al. 2020

Journal of Asian Ceramic Societies

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Subsolidus Bi 3.36 Fe 2.08+x Nb 2.56−x O 14.56−x (BFN) pyrochlores prepared by solid-state reaction at 950°C over 48 h showed a moderate solid solution range of −0.24 ≤ x ≤ 0.48. As to preserve the overall charge electroneutrality of the system, the doping mechanism was proposed to be a one-to-one substitution of Nb 5+ by Fe 3+ together with oxygen non-stoichiometry, i.e. Nb 5+ ↔ Fe 3+ − O 2-. BFN pyrochlores crystallized in a cubic symmetry, space group Fd � 3m (No. 227), Z = 4 and their refined lattice constants were found to be in the range 10.5071 (4)-10.5107 (7) Å. The microstructural analyses revealed their grain size range 0.5-8.4 μm and crystallite size range 63 −78 nm, respectively. These thermally stable BFN pyrochlores exhibited moderate high dielectric constants, ε' in the range 141-150 and dielectric losses, tan δ ~ 0.2 at ~30°C and 1 MHz.

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Electrochemical properties of complex pyrochlores

Piir,

Koroleva,

Krasnov

2022

Pyrochlore Ceramics

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Li- and Mg-codoped bismuth niobate pyrochlores: Synthesis, structure, electrical properties

Cited by 12 publications

References 46 publications

Ab Initio and Experimental Insights on Structural, Electronic, Optical, and Magnetic Properties of Cr-Doped Bi₂Ti₂O₇

Ab Initio and Experimental Insights on Structural, Electronic, Optical, and Magnetic Properties of Cr-Doped Bi₂Ti₂O₇

Investigation of structural and dielectric properties of subsolidus bismuth iron niobate pyrochlores

Electrochemical properties of complex pyrochlores

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Li- and Mg-codoped bismuth niobate pyrochlores: Synthesis, structure, electrical properties

Cited by 12 publications

References 46 publications

Ab Initio and Experimental Insights on Structural, Electronic, Optical, and Magnetic Properties of Cr-Doped Bi2Ti2O7

Ab Initio and Experimental Insights on Structural, Electronic, Optical, and Magnetic Properties of Cr-Doped Bi2Ti2O7

Investigation of structural and dielectric properties of subsolidus bismuth iron niobate pyrochlores

Electrochemical properties of complex pyrochlores

Contact Info

Product

Resources

About

Ab Initio and Experimental Insights on Structural, Electronic, Optical, and Magnetic Properties of Cr-Doped Bi₂Ti₂O₇

Ab Initio and Experimental Insights on Structural, Electronic, Optical, and Magnetic Properties of Cr-Doped Bi₂Ti₂O₇