Synthesis and characterization of the pyrochlore Bi1.56Sb1.48−xNbxCo0.96O7 solid solution

Sellami, Mayouf; Caignaert, V.; Bekka, Ahmed; Bettahar, Noureddine

doi:10.1016/j.jallcom.2009.12.059

Cited by 20 publications

(9 citation statements)

References 24 publications

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“…Pyrochlore compounds are interesting due to their different physical properties, which depend on the chemical composition and the applied method of synthesis. The wide range of the cationic radius ratio 1.46 < r (A 3+ )/ r (B 4+ ) < 1.80 (“pyrochlore field” for A 3+ 2 B 4+ 2 O 7 ), the possibility of the substitution either A- or B-site atoms, , and stability with the presence of vacancies , allow designing new pyrochlore compounds with miscellaneous properties . Bismuth titanate pyrochlore Bi 2 Ti 2 O 7 (BTO) is such an outstanding example. − New doped BTO pyrochlores may be potentially used as dielectric materials at room temperatures, − as mixed electronic-ionic conductors at intermediate temperatures for developing electrochemical devices, as luminescence compounds, − and in photocatalytic applications. − …”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

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

et al. 2019

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“…[23][24][25][26][27][28][29] Thus, Method 1 initiated investigations on the synthesis of Ca 2 Ru 2 O 7-y . [23][24][25][26][27][28][29] Thus, Method 1 initiated investigations on the synthesis of Ca 2 Ru 2 O 7-y .…”

Section: Resultsmentioning

confidence: 99%

Carbonate Selective Ca₂Ru₂O_7-yPyrochlore Enabling Room Temperature Carbonate Fuel Cells

Vega

Shrestha

Ignatowich

et al. 2011

J. Electrochem. Soc.

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Synthesis of a carbonate selective Ca 2 Ru 2 O 7-y catalyst was investigated using solid-state and hydrothermal routes. The resulting materials were physically characterized by x-ray diffraction, BET gas adsorption, scanning electron microscopy and temperature programmed desorption. The solid-state reaction of precursor oxides, CaO and RuO 2 , led to the formation of a perovskite phase. A hydrothermal route using O 2 as an oxidizing agent yielded a mostly amorphous phase primarily comprised of unreacted precursor. The use of low concentration KMnO 4 (10 mM) as a replacement for O 2 in the hydrothermal synthesis, in combination with high pH (∼14) and moderate temperature (200 • C), yielded a highly crystalline, thermally stable Ca 2 Ru 2 O 7-y pyrochlore. The increase in crystallinity was attributed to the ability of permanganate to maintain ruthenium in the +5 oxidation state required for formation of the pyrochlore phase. Micron-sized primary particles with a high density of ∼ 50 nm surface nanocrystallites were obtained. The presence of the nanocrystallites gave the pyrochlore a high surface area, 174 m 2 /g. The pyrochlore showed preferential surface adsorption of CO 2 compared to H 2 O, making it a feasible candidate for a carbonate selective catalyst. This preferential adsorption was attributed to the use of calcium, an alkaline earth metal, which gave the pyrochlore a high surface basicity.

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“…In this Bi 2 O 3 -ZnO-Nb 2 O 5 pyrochlores, NbO 6 and ZnO 6 octahedra with shared vertices form a three-dimensional network resulting in large cavities which contain the O 0 and A site atoms in an A 2 O 0 tetrahedral net [14]. It has considerable compositional and structural flexibility, including the possibility to incorporate a wide range of dopant ions [15][16][17]. Thus ion substitution, such as Mg 2?…”

Section: Introductionmentioning

confidence: 99%

Effect of Sn4+ and W6+ substitution on the dielectric properties of Bi2O3–ZnO–Nb2O5-based low firing ceramics

Zhang

et al. 2016

J Mater Sci: Mater Electron

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As a promising candidate for thermostable Lowtemperature co-fired ceramic material with NP0 characteristic, (Bi 1.8 Zn 0.2 )(Zn 0.6 Nb 1.4-2x Sn x W x )O 7 (x = 0.00, 0.02, 0.05, 0.10) dielectric ceramics with improved dielectric properties were prepared by conventional mixed oxide route. The effect of the chemical substitution of Sn 4? and W 6? cations on the structure and dielectric properties in this system had been investigated systematically. The Sn 4? and W 6? co-substitution was tentatively introduced in cubicmonoclinic pyrochlores co-existing ceramics and the results showed regular influence on the structure, dielectric properties with the amount of substitution. With the structure evaluation and electrical properties measurement results, the Sn 4? and W 6? substituted Nb 5? in B site showed an effective way to depress the grain growth and the ceramic with fine grains in 1-3 lm that can be obtained at a low sintering temperature of 950°C. Based on these results, small amount of Sn 4? and W 6? substitution was successfully applied to a base ceramic with the electrical properties, which can be a promising candidate for LTCC and multilayer components applications in high frequency and microwave range.

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Synthesis and characterization of the pyrochlore Bi1.56Sb1.48−xNbxCo0.96O7 solid solution

Cited by 20 publications

References 24 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

Carbonate Selective Ca₂Ru₂O_7-yPyrochlore Enabling Room Temperature Carbonate Fuel Cells

Effect of Sn4+ and W6+ substitution on the dielectric properties of Bi2O3–ZnO–Nb2O5-based low firing ceramics

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Synthesis and characterization of the pyrochlore Bi1.56Sb1.48−xNbxCo0.96O7 solid solution

Cited by 20 publications

References 24 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

Carbonate Selective Ca2Ru2O7-yPyrochlore Enabling Room Temperature Carbonate Fuel Cells

Effect of Sn4+ and W6+ substitution on the dielectric properties of Bi2O3–ZnO–Nb2O5-based low firing ceramics

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Product

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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

Carbonate Selective Ca₂Ru₂O_7-yPyrochlore Enabling Room Temperature Carbonate Fuel Cells