Lanthanum Aluminate Research Articles

Effect of citric acid quantity on LaAlO3 formation in sol-gel synthesis with combustion

Lanthanum aluminate (LaAlO3) was synthesized using the nitrate-citrate sol-gel method followed by the combustion process. The synthesis was conducted using fuel-lean at pH 7, with metal precursor to citric acid mass ratios (Me:C₆H₈O₇) of 1:0.25, 1:0.37, and 1:0.48. The resultant products were analyzed using X-ray diffraction and scanning electron microscopy (SEM). After post-annealing at 900 °C, the formation of crystalline LaAlO3 was confirmed, whereas the as-pyrolized product was found to be X-ray amorphous. It was established through thermal analysis that nitrate-citrate complexes decompose in several stages, and LaAlO3 crystallizes at around 840 °C. An increase in citric acid concentration correlated with a reduction in microstress levels and a decrease in the size of coherent scattering regions, in agreement with the particle size measurement results obtained from SEM images. The synthesized nanoscale particles exhibited an average size in the range of 50–60 nm and a specific surface area greater than 15 m²/g. The synthesized powders were characterized by fragile porous aggregates composed of thin porous walls. Notably, an increase in citric acid concentration promoted the enlargement of pores within the aggregates while simultaneously reducing the pore size within the thin walls. Furthermore, the materials synthesized from the solutions with pH 1 demonstrated a larger average particle size (~75 nm) and smaller pore sizes, with combustion occurring at lower temperatures compared to the samples obtained from the solutions at pH 7.

Enhancing Thermal Stability of PVC Through Organic Acid‐Interlayered Hydrotalcite Modification: Experimental and Computational Analysis

ABSTRACTThis study systematically examines the effects of diphenylphosphinic acid (DPPA) and sarcosine (SAR) intercalation into magnesium aluminum lanthanum hydrotalcite (LDHs) on its structure and thermal stability. Using charge distribution, structural optimization, energy calculations, XRD, FTIR, TEM, and thermal stability tests, the study reveals that DPPA anions, with higher negative charge density, increase the interlayer spacing to 6.08 Å and exhibit a binding energy of −0.7624 eV. SAR anions, with a thinner interlayer spacing of 4.11 Å and a binding energy of −1.603 eV, create a more stable structure. SAR's higher dipole moment (2.827 a.u.) compared to DPPA (2.077 a.u.) enhances electrostatic interactions. Thermal stability tests show SAR‐LDHs and DPPA‐LDHs extend PVC's stability to 53.67 and 56.67 min, respectively. DPPA anions provide superior stability at high temperatures, while SAR anions excel in moderate temperatures. This study offers insights for designing thermally stable composite materials.

Preparation of Zinc–Lanthanum and Zinc–Aluminum–Lanthanum Layered Double Hydroxides and Analysis of Their Thermal Stabilization Mechanism on PVC

Preparation of Zinc–Lanthanum and Zinc–Aluminum–Lanthanum Layered Double Hydroxides and Analysis of Their Thermal Stabilization Mechanism on PVC

The Effect of Diphenylphosphate Intercalated Magnesium Aluminum Lanthanum Hydrotalcite on the Thermal Stability and Mechanical Properties of Poly(Vinyl Chloride)

The Effect of Diphenylphosphate Intercalated Magnesium Aluminum Lanthanum Hydrotalcite on the Thermal Stability and Mechanical Properties of Poly(Vinyl Chloride)

Nickel nanocatalyst on lanthanum aluminate: Optimizing preparation and evaluating performance in glycerol dry reforming for syngas production

In this study, mesoporous nanocrystalline Ni/La-Al catalysts with varying nickel (Ni) loadings (5, 10, 15, and 20 wt.%) were synthesized using a solid-state method for the glycerol dry reforming (GDR) reaction. The effects of different Ni loadings and the addition of steam on the structural and catalytic performance of the catalysts were investigated. Characterization techniques, including Brunauer-Emmett-Teller (BET) surface area analysis, temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), and X-ray diffraction (XRD) were employed to analyze the catalysts' properties. Results showed that increasing Ni loading to 10 wt.% improves the catalytic properties. However, by increasing the Ni loading, a decrease in catalytic properties due to increasing particle size, creating NiO bulk phase and surface pore blockage is obvious. A series of experiments were performed to investigate the effect of steam usage on catalytic properties. TPO analysis revealed that steam addition reduces the carbon deposition and shifts oxidation peaks to lower temperatures; consequently, the activity and stability of the catalyst will be enhanced. Although the 5 - 7.5 vol.% of steam in the feed composition significantly stabilizes the catalyst, it is possible to produce H2-rich synthesis gas, and conversely, increasing the temperature reduces the H2/CO ratio. Various examinations were conducted under different conditions, including varying gas hourly space velocity (GHSV), carbon-to-glycerol ratio (CGR), and temperature, to obtain more comprehensive data on the catalysts.

Study on reaction interface of carbon‐free oxide‐based refractories with lanthanum oxide and lanthanum aluminate

AbstractIn this study, the reaction interfaces of four kinds of oxide refractories (corundum, spinel, mullite, and zirconia) with lanthanum oxide (La2O3) and lanthanum aluminate (LaAlO3) under different atmospheres at high temperatures (1550°C) were analyzed. The results show that the four oxides have a strong reaction with La2O3, and the corresponding rare earth aluminate, rare earth silicate, and rare earth zirconate are formed respectively. The reaction with LaAlO3 is weak, and almost no reaction occurs. Mullite has poor structural stability in a high‐temperature reduction atmosphere, easy decomposition, and strong reaction with La2O3. This study provides an important reference for the study of the reaction mechanism between rare earth steel and lining materials and the research and development of special lining materials for rare earth steel.

Effect of calcination temperature on structural, optical, and morphological properties of RAlO3 (R = La, Sm) perovskite oxides

RAlO3 (R = La, Sm) have attracted the research community due to their interesting optoelectronic properties and viable applications. The solution combustion method allows for a faster process and lower calcination temperature than the traditional solid-state method and is an economical alternative to wet chemical synthesis for producing RAlO3. This work explores the thermal, structural, morphological, optical, and electrical properties of RAlO3 (R = La, Sm) synthesised by the solution combustion method using urea as fuel. Thermogravimetric analysis—differential thermal analysis (TGA-DTA) showed the crystallization temperatures of lanthanum aluminate (LaAlO3) and samarium aluminate (SmAlO3) at 864 and 887 °C, respectively. The x-ray diffraction (XRD) and Rietveld analysis revealed the structure of LaAlO3 as rhombohedral (R-3c) and SmAlO3 as orthorhombic (Pbnm). The LaAlO3 and SmAlO3 samples calcinated at 800 °C showed crystallite size (D) of 19.26 nm and 19.06 nm, respectively. The field emission scanning electron microscopy (FE-SEM) images show a highly porous and large sheet-like morphology with voids and cracks. High resolution transmission electron microscopy (HR-TEM) images and the selective area electron diffraction (SAED) pattern show crystalline nature and the indexed planes agreed with the XRD results. The LaAlO3 and SmAlO3 samples had specific surface areas of 16.374 and 12.953 m2 g−1, respectively. The TGA-DTA results were affirmed by Fourier transform infrared spectroscopy (FT-IR) results which showed only the presence of metal-oxide bonds for materials annealed at and above 800 °C. These results were further validated by the electron dispersive x-ray spectroscopy (EDX) and the x-ray photoelectron spectroscopy (XPS) showing no additional peaks. The band gap of 5.08 and 4.82 eV were calculated from ultraviolet-visible spectroscopy (UV–vis) for LaAlO3 and SmAlO3, respectively. The results imply that the solution combustion technique using urea as fuel is a viable route for synthesising RAlO3.

Composite Nano Lanthanum Aluminate Synthesized by Phytocombustion Method: Energy Storage Devices, Sensing and Biological Applications

Composite Nano Lanthanum Aluminate Synthesized by Phytocombustion Method: Energy Storage Devices, Sensing and Biological Applications

Engineering Oxide Epitaxy beyond Substrate Constraint.

Orientation engineering is a crucial aspect of thin film growth, and it is rather challenging to engineer film epitaxy beyond the substrate constraint. Guided by density functional theory calculations, we use SrRuO3 (SRO) as a buffer layer and successfully deposit [111]-oriented CoFe2O4 (CFO) on [001]-, [110]-, and [111]-oriented SrTiO3 (STO) substrates. This enables subsequent growth of [111]-oriented functional oxides, such as PbTiO3 (PTO), overcoming the constraint of the substrate. This strategy is quite general and applicable to lanthanum aluminate and yttria-stabilized zirconia substrates as well. X-ray Φ scans and atomic resolution aberration-corrected scanning transmission electron microscopy (AC-STEM) reveal detailed epitaxial relations in each of the cases, with four variants of [111]-CFO found on [001]-STO and two variants found on [110]-STO, formed to mitigate the large lattice misfit strain between the film and substrate. Our strategy thus provides a general pathway for orientation engineering of oxide epitaxy beyond substrate constraint.

Novel Tb³⁺-Doped LaAl₂B₄O₁₀ phosphors: Structural analysis, luminescent properties, and energy transfer mechanism

This study explores the structural and luminescent properties of terbium (Tb³⁺)-doped lanthanum aluminium borate (LaAl₂B₄O₁₀, abbreviated as LAB) phosphors, a novel host lattice for Tb³⁺ doping. LAB:Tb³⁺ phosphors, with varying dopant concentrations, were synthesized using a microwave-assisted combustion synthesis approach and characterized using X-ray diffraction (XRD), Rietveld refinement, and photoluminescence spectroscopy at both room and low temperatures. The structural analysis confirmed the hexagonal crystal structure of LAB and revealed successful incorporation of Tb³⁺ ions without altering the fundamental lattice. Luminescence studies demonstrated that the LAB:Tb³⁺ phosphors show strong green emission primarily attributed to the 5D4→7F5 transition of Tb³⁺. The optimal doping concentration was determined to be 5 wt% Tb³⁺, which provided maximum luminescence efficiency. This concentration also allowed for a critical study of energy transfer mechanisms within the phosphor, revealing dipole-dipole interactions with a critical distance of 9.80 Å between Tb³⁺ ions. Additionally, the CIE chromaticity coordinates of LAB:0.05 Tb³⁺ were precisely determined to be (0.289, 0.4460), indicating the potential for high-quality green emission suitable for solid-state lighting and display technologies. This work not only demonstrates the potential of LAB:Tb3+ as a highly efficient green luminescent material, but also sheds light on the mechanisms responsible for energy transfer and concentration quenching.

Orangish-red light emitting LaSr2AlO5:Sm3+ nanophosphors for warm LEDs: Crystallographic, photoluminescence characteristics with high color purity and thermal stability

Gel-combustion method was implemented in current research to generate Strontium Lanthanum Aluminate (LaSr2AlO5) phosphors doped with Sm3+ ions and have a potential to emit orangish-red light. In order to analyze phase characteristics, XRD technique was employed. XRD patterns of synthesized materials were closely resembles the JCPDS pattern indicated on card no. 70–2197, which define the tetragonal symmetry of the material with I4/mcm space group. The morphological, optical band energies and elemental analyses were done via TEM, DRS and EDX investigation respectively. The Sm3+ activated LaSr2AlO5 phosphor's PL spectra monitored at 406 nm excitation indicate intense visible orangish-red emission at 602 nm owing to the 4G5/2 → 6H7/2 transition. Concentration quenching was obtained at 4 mol % content of Sm3+ owed to the dipole-dipole interaction among activated ions. The calculated lifetimes have been observed to shorten as content of Sm3+ ions in the phosphors rises. The CIE (0.6069, 0.3905) value, CCT (1382 K) value, 99.4 % color purity of the optimum sample was calculated which placed in orange-red space. The fabricated phosphor has excellent thermal durability up to 498 K and 0.1686 eV activation energy. Finally, the results of all the research allow us to consider that Sm3+ doped LaSr2AlO5 phosphor is appropriate for warm LEDs.

Synthesis of Niobium Pentoxide and Its Reduced Graphene Oxide Nanocomposite for Enhanced Supercapacitor Applications

Synthesis of Niobium Pentoxide and Its Reduced Graphene Oxide Nanocomposite for Enhanced Supercapacitor Applications

Optimizing the Structure and Optical Properties of Lanthanum Aluminate Perovskite through Nb5+ Doping.

This work involves the introduction of niobium oxide into lanthanum aluminate (LaAlO3) via a conventional solid-state reaction technique to yield LaAlO3:Nb (LaNbxAl1-xO3+δ) samples with Nb5+ doping levels ranging from 0.00 to 0.25 mol%. This study presents a comprehensive investigation of the effects of niobium doping on the phase evolution, defect control, and reflectance of LaNbxAl1-xO3+δ powder. Powder X-ray diffraction (XRD) analysis confirms the perovskite structure in all powders, and XRD and transmission electron microscopy (TEM) reveal successful doping of Nb5+ into LaNbxAl1-xO3+δ. The surface morphology was analyzed by scanning electron microscopy (SEM), and the results show that increasing the doping concentration of niobium leads to fewer microstructural defects. Oxygen vacancy defects in different compositions are analyzed at 300 K, and as the doping level increases, a clear trend of defect reduction is observed. Notably, LaNbxAl1-xO3+δ with 0.15 mol% Nb5+ exhibits excellent reflectance properties, with a maximum infrared reflectance of 99.7%. This study shows that LaNbxAl1-xO3+δ powder materials have wide application potential in the field of high reflectivity coating materials due to their extremely low microstructural defects and oxygen vacancy defects.

A New Approach to Fuel Cell Electrodes: Lanthanum Aluminate Yielding Fine Pt Nanoparticle Exsolution for Oxygen Reduction Reaction

AbstractDesigning an electrocatalyst with low Pt content is an immediate need for essential reactions in low temperature fuel cell systems. In the present work, La0.9925Ba0.0075Al0.995Pt0.005O3 is aimed at using with low (only 0.5%) Pt doping as an electrocatalyst for oxygen reduction reaction (ORR). The low doping level renders exsolution of 1–2 nm nanoparticles with uniform dispersion upon reduction in H2/N2 at low temperatures. Pt exsolved perovskite oxides deliver significantly enhanced catalytic activity for ORR and improved stability in alkaline media. This study demonstrates that LaAlO3 with low noble metal content holds immense potential as an electrocatalyst in real fuel cell systems.

Synthesis and physical investigation of Al doped La2O3 thin films for wettability applications

AbstractIn this work, aluminum doped La2O3 thin films deposited by the spray pyrolysis technique, are investigated by many characterization techniques. First, XRD spectra reveal the presence of two phases. A dominant cubic phase is obtained for pure La2O3 with (220) preferential orientation. The second hexagonal phase with (004) orientation is present in all doped samples. It is found that Al doping induces a perovskite crystalline structure identified as lanthanum aluminate (LaAlO3). Second, FTIR spectra include the main peaks of La‐O bonds related to La2O3 structure. Photoluminescence (PL) shows a good enhancement by Al doping related to LaAlO3 nanoparticles. Finally, the surface wettability measurements corroborate the hydrophobic character of all doped samples.

Modulation of the optical and transport properties of epitaxial SrNbO3 thin films by defect engineering

The discovery of strontium niobate (SNO) as a potentially new transparent electrode has generated much interest due to its implications in various optoelectronic devices. Pristine SNO exhibits exceptionally low resistivity (∼10−4 Ω cm) at room temperature. However, this low resistivity occurs due to large number of carrier concentration in the system, which significantly affects its optical transparency (∼40%) in the visible range and hinders its practical applications as a transparent electrode. Here, we show that modulating the growth kinetics via oxygen manipulation is a feasible approach to achieve the desired optoelectronic properties. In particular, epitaxial (001) SNO thin films are grown on (001) lanthanum aluminate by pulsed laser deposition at different oxygen partial pressures and are shown to improve the optical transparency from 40% to 72% (λ = 550 nm) at a marginal cost of electrical resistivity from 2.8 to 8.1 × 10−4 Ω cm. These changes are directly linked with the multi-valence Nb-states, as evidenced by x-ray photoelectron spectroscopy. Furthermore, the defect-engineered SNO films exhibit multiple electronic phases that include pure metallic, coexisting metal-semiconducting-like, and pure semiconducting-like phases as evidenced by low-temperature electrical transport measurements. The intriguing metal-semiconducting coexisting phase is thoroughly analyzed using both perpendicular and angle-dependent magnetoresistance measurements, further supported by a density functional theory-based first-principles study and the observed feature is explained by the quantum correction to the conductivity. Overall, this study shows an exciting avenue for altering the optical and transport properties of SNO epitaxial thin films for their practical use as a next-generation transparent electrode.

Tunable laser operations on Nd-doped strontium and lanthanum aluminate crystals

We reported on tunable laser operations in a disordered Nd-doped strontium-lanthanum aluminate (Nd:ASL) crystal, corresponding to the formula Sr1-xNdyLax-yMgxAl12-xO19. We conducted tunable laser experiments in a V-fold cavity with a birefringence filter within the resonator for the first time. The Nd:ASL laser operating at three peak wavelengths (1050, 1062, and 1074 nm) was demonstrated. The results indicated that the wavelength tuned in two separate ranges: 1049.59–1054.43 nm and 1059.71–1078.18 nm. The multi-wavelength feature was also observed in the experiments.

Facile synthesis of an Ni/LaAlO3 – Perovskite via an MOF gel precursor for the dry reforming of methane

A simple strategy to prepare the pure perovskite phase of lanthanum aluminate (LaAlO3) by calcination of a highly porous, dry MOF precursor gel has been developed. This study demonstrates that the structural and textural properties, such as specific surface area, pore volumes and pore sizes, of precursor-like metal–organic gels (MOG) (MOG-Al-La) based on metal–organic framework (MOF) structures can be modulated by optimizing the solvothermal treatment time. The perovskite obtained after solvothermal treatment at 120 °C for 12 h and calcination at 750 °C maintained the mesoporous characteristics of the MOF precursor, with a small particle size due to the decrease in crystallization temperature. These properties in the support allowed a good dispersion of the active Ni sites, low reducibility, and a strong interaction between them and the support, thus suppressing sintering under the severe catalytic reaction conditions evaluated (GHSV = 120,000 cm3/g·h) for the dry reforming of methane. The resulting MOX-(12 h)-LaAlO3-750-Ni catalyst gave a CH4 average conversion of 75% and CO2 average conversion of 80% after 20 h of reaction. The improved stability of the catalyst was attributed to suppression of the formation of the dense network of carbon filaments that can stress and subsequently fracture the support, cause attrition of the catalyst granules and hinder diffusion of the reactants both through the pores of the support and the interparticle spaces.

Structural Features of Lanthanum Aluminum Mixed Oxides and Stability of Their Catalytic Properties in Oxidative Coupling of Methane

Structural Features of Lanthanum Aluminum Mixed Oxides and Stability of Their Catalytic Properties in Oxidative Coupling of Methane

Synchrotron studies of Ag+ and Dy3+ ions in zinc lanthanum aluminum borate glasses synthesized using Novel Microwave melt-quenching technique

A novel microwave heating technique is used in the present work to synthesis the glasses. In this work, the stoichiometry ratio of (43-x) B2O3+ 45ZnO+ 5La2O3+ 5Al2O3+ 0.5SnO2+ 1.5AgNO3+ xDy2O3 were exposed to microwave energy, with 800-W power, holding time was 26 min to synthesize by novel melting in microwave and quenched suddenly. The study focused on borosilicate glasses such as physical, optical, and luminescent characteristics. The prepared glasses were subjected to evaluate density, molar volume, and refractive index. The optical absorption spectra of glasses were measured in the range of 200–2000 nm. The surface plasmon resonance of AgNPs peaks resonates with the radiative transitions of Dy2O3 ions at 429 nm. The emission spectra in the visible region showed three peaks in the range 450–700 nm, and the excitation spectra of developed glass samples in the range of 200–500 nm, most intense peak was observed at 351 nm. Asymmetry ratio enhancement was achieved by changing the excitation wavelength and silver nanoparticle concentration. The highest Y/B value of 1.532 was observed at 1.0 mol%. The non-exponential lifetime decay curves of 0.3, 0.5, and 1.0 mol%, show 0.337, 0.376, and 0.269 ms respectively. J-O parameter shows trend Ω2 > Ω6 > Ω4. Synchrotron studies were subjected to comprehend the coordination chemistry of silver nanoparticles, dysprosium ions, and correlated with the results obtained.