Application of lanthanum to pseudo-boehmite and γ-Al2O3

Tijburg, I. I. M.; Geus, J.W.; Zandbergen, H.W.

doi:10.1007/bf02387833

Cited by 40 publications

(4 citation statements)

References 5 publications

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“…Of these promoters, La 3+ is the most widely used in industry . Numerous studies have shown that La 3+ dopant percentages of 3–5 wt % are sufficient to achieve the stabilizing effect, ,− though several studies have indicated that loadings as low as ∼0.5 wt % may be sufficient. , Increasing the La percentage beyond 5% appears to diminish the surface area and pore structure of the Al 2 O 3 support and may have negative effects on the activity of some catalysts. , Thus, a La dopant level of about 3 wt % is generally considered to be optimal. − …”

Section: Introductionmentioning

confidence: 99%

La-Dopant Location in La-Doped γ-Al₂O₃ Nanoparticles Synthesized Using a Novel One-Pot Process

et al. 2015

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We have recently developed a 'solvent-deficient' method of synthesizing high surface area γ-Al 2 O 3 nanoparticles that show promise for catalyst support applications. Here, we investigate doping the alumina with La 3+ to stabilize the gamma phase to higher temperatures. The One-pot method for synthesizing La-doped γ-Al 2 O 3 nanoparticles developed here has several advantages over conventional methods including requiring only 3 hours instead of 3 days and wasting no lanthanum.TEM, X-ray PDF, and BET analyses as a function of calcination temperature show that the La stabilizes the gamma phase by 100°C. In order to begin understanding the mechanism of stabilization, the location of the La 3+ atoms in our doped γ-Al 2 O 3 nanoparticles is investigated via X-ray PDF and EXAFS analyses which indicate that the La dopant adsorbs as single, isolated atoms on the γ-Al 2 O 3 surface. As calcination temperature increases, the immediate oxygen coordination shell of the La becomes increasingly like La 2 O 3 though an extended La 2 O 3 lattice is not formed due to the sparse (3 wt%) concentration of La atoms. During the γ-to-α transition, the La environment changes drastically to become more like LaAlO 3 than La 2 O 3 , suggesting that the La is enveloped by the alumina lattice during the alpha phase transition though an extended LaAlO 3 lattice is not formed.

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Section: Introductionmentioning

confidence: 99%

La-Dopant Location in La-Doped γ-Al₂O₃ Nanoparticles Synthesized Using a Novel One-Pot Process

et al. 2015

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“…When structural changes to the starting alumina are avoided, the doped product will have properties (e.g., pore size distributions) similar to the alumina from which it was obtained. 96 Apart from impregnation, 22,27,28,32,33,51,52,55,61,69,73,77,78,81,85, 89,100,104−112 other doping methods include deposition by precipitation, 78,107 hydrothermal treatment, 91 coprecipitation, 26,83,113 sol−gel synthesis, 34,52,53,58,63,64,66,76,79,93,98,106,114 combustion synthesis, 8 nitrate decomposition, 76 and other solvent-free or solid-state reactions. 16,52,76,94 However, it appears to be difficult to achieve an adequate dispersion of lanthanum on alumina by solid-state reactions.…”

Section: Stabilization Of Transition Aluminas By Dopantsmentioning

confidence: 99%

“…Apart from impregnation, , , ,, , ,, , ,, , , , , , , , − other doping methods include deposition by precipitation, , hydrothermal treatment, coprecipitation, ,, sol–gel synthesis, , , , , , , , , ,, , , combustion synthesis, nitrate decomposition, and other solvent-free or solid-state reactions. , , , However, it appears to be difficult to achieve an adequate dispersion of lanthanum on alumina by solid-state reactions. E.g., Huang et al observed no stabilizing effect (at 1200 °C) for samples prepared by calcination of mechanically mixed boehmite and LaAlO 3 or La 2 O 3 .…”

Section: Temperature Stabilization Of Aluminasmentioning

confidence: 99%

La-Doped Alumina, Lanthanum Aluminate, Lanthanum Hexaaluminate, and Related Compounds: A Review Covering Synthesis, Structure, and Practical Importance

Heveling

2023

Ind. Eng. Chem. Res.

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Advanced materials based on lanthanum–aluminum oxides are useful for many practical applications, not the least in catalysis, energy conversion and energy storage systems designed for a sustainable world economy. The three main La–Al–O (LAO) combinations of commercial interest are La-doped aluminas (LDA), lanthanum monoaluminate (LMA, a perovskite), and lanthanum hexaaluminate (LHA). Usually, the literature treats doped aluminas, perovskites, and hexaaluminates separately. The current review tries to identify common trends and features with respect to structure, synthesis, and applications of LAOs, which should lead to a more holistic understanding of their chemistry. This, in turn, should trigger innovative ideas with respect to new or improved applications. Apart from a variety of uses at low temperatures, the main advantages of LDA, LMA, LHA, and related compounds are their high-temperature stability and the extended applicability that comes with it.

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“…First of all, it has been observed experimentally that the solubility of Lanthanum in perovskite materials such as lead titanate (PbTiO 3 ), lead zirconate (PbZrO 3 ), lithium tantalate (LiTaO 3 ), barium titanate (BaTiO) and niobate (LiNbO 3 ) [26] is critically lower [27,28], which limits higher dopant concentration in the host lattices. Secondly La prone to form secondary phases with oxygen upon higher doping concentration (even 5%-10%), thereby adding further un-clarity in understanding the role of Lanthanum on structural and optical modifications of perovskites and oxides [29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Electronic and optical behaviour of lanthanum doped CaTiO₃ perovskite

Rizwan

Usman

Shakil

et al. 2020

Mater. Res. Express

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To improve the efficiency of perovskite based solar cells, doping of heavier elements in Perovskite materials (ABX 3 ) can modulate its electronic and optical properties significantly. Thus it is important to understand the possible microscopic origin of the band gap modification and optical enhancement after heavier element doping using first-principles studies. Here we investigate the effect of La doping, while substituting the Ca atom, on the electronic and optical properties in CaTiO 3 perovskite material using generalized gradient approximation within density functional theory. We observe a decrease in lattice constants and bond lengths in La x Ca 1−x TiO 3 , mainly due to re-distribution of electronic charge density between La and Oxygen, as confirmed by charge density contour. We further notice a widening of electronic band gap and an upward shift of Fermi level into the conduction band, thus characterizing La x Ca 1−x TiO 3 as an n-type material. DOS diagram attributes this shift mainly due to the appearance of La p-DOS and d-DOS and their repulsion with N p-DOS, when La enters into the host lattice at Ca site. Investigation of optical properties upon La Doping in CaTiO 3 exhibits further shifting of polarization and refractive index to lower values as compared to its pure counterpart, due to dominating semiconducting behavior and hence one observes a blue shift in absorption and reflection spectrum accordingly. Energy loss function is found to be consistent with absorption and extinction coefficient measured in case of La x Ca 1−x TiO 3 . All these results are found to be consistent with the existing experimental and first-principles studies.

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Application of lanthanum to pseudo-boehmite and γ-Al2O3

Cited by 40 publications

References 5 publications

La-Dopant Location in La-Doped γ-Al₂O₃ Nanoparticles Synthesized Using a Novel One-Pot Process

La-Dopant Location in La-Doped γ-Al₂O₃ Nanoparticles Synthesized Using a Novel One-Pot Process

La-Doped Alumina, Lanthanum Aluminate, Lanthanum Hexaaluminate, and Related Compounds: A Review Covering Synthesis, Structure, and Practical Importance

Electronic and optical behaviour of lanthanum doped CaTiO₃ perovskite

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Application of lanthanum to pseudo-boehmite and γ-Al2O3

Cited by 40 publications

References 5 publications

La-Dopant Location in La-Doped γ-Al2O3 Nanoparticles Synthesized Using a Novel One-Pot Process

La-Dopant Location in La-Doped γ-Al2O3 Nanoparticles Synthesized Using a Novel One-Pot Process

La-Doped Alumina, Lanthanum Aluminate, Lanthanum Hexaaluminate, and Related Compounds: A Review Covering Synthesis, Structure, and Practical Importance

Electronic and optical behaviour of lanthanum doped CaTiO3 perovskite

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La-Dopant Location in La-Doped γ-Al₂O₃ Nanoparticles Synthesized Using a Novel One-Pot Process

La-Dopant Location in La-Doped γ-Al₂O₃ Nanoparticles Synthesized Using a Novel One-Pot Process

Electronic and optical behaviour of lanthanum doped CaTiO₃ perovskite