Introduction Of Lanthanum Research Articles

Enhanced Thermodynamic Stability of Delithiated Nano-LiCoO2 by Lanthanum Doping.

The dynamic environment within lithium-ion batteries induces significant changes in local thermodynamic functions, hampering the accurate prediction of the stability of the cathodes during cycling. While delithiation primarily affects the surface properties of the cathode structure, there is a lack of fundamental understanding concerning the evolution of interfacial energies with varying stoichiometry. Here, we used microcalorimetry to quantify the thermodynamic changes between the stoichiometric and partially delithiated nano-LiCoO2 states for the first time. A mild delithiation from LiCoO2 to Li0.71CoO2 caused a surface energy reduction, negatively affecting the adhesion between adjacent grains by ∼0.4J/m2. The introduction of lanthanum at 1.0 atom % reduced the surface energy of the stoichiometric LiCoO2 while forcing a constant surface energy state during delithiation down to Li0.57CoO2. This reduced the thermodynamic stress between grains during lithium cycling, mitigating degradation mechanisms. The lanthanum-induced surface stabilization also inhibited the coarsening and dissolution of the cathode particles. We used electron microscopy to propose an atomistic mechanism by which the lanthanum doping pins surface dissolution for improved cathode stability.

G-C3N4/La2O3 nanocomposite as a photo-electrocatalyst in solar water splitting

The enhancement of g-C3N4 photocatalytic performance is most effectively achieved through doping or composite incorporation. Notably, rare-earth element nanocomposites, characterized by their exclusive 4f electronic configuration, have demonstrated remarkable potential in boosting photocurrent density. In this study, we successfully prepared a Lanthanum (La)-incorporated g-C3N4 composite using the methanolic dispersion method, resulting in a photostable photoanode. The optimized g-C3N4 composite, featuring approximately ∼59.8 % La composition, exhibited a substantial photocurrent of approximately ∼10.16 μA cm−2, a significant improvement compared to the unaltered g-C3N4, which only achieved about 4.56 μA cm−2 at 1.23 vs. Ag/AgCl. The introduction of lanthanum into the composite modified the elemental composition by introducing oxygen-doping into the g-C3N4 structure. Additionally, the unique dual nanostructures, comprising nanoparticles and nanoflakes, played a crucial role in enhancing catalytic sites, increasing surface area, and improving light absorption. According to the BET analysis, the N2 adsorption–desorption isotherms reveal that the SBET of g-C3N4/la2O3–59.8 % is approximately 74.84 m2 g−1, surpassing the surface area of pristine g-C3N4, which is approximately 65.32 m2 g−1. Moreover, the formation of the nanocomposite contributed to a reduction in the band gap from 2.82 eV (pure g-C3N4) to 2.74 eV (g-C3N4/La-59.8 %). In conclusion, due to its exceptional photostability and remarkable performance, the g-C3N4/La2O3 nanocomposite exhibits significant promise as a potential candidate in the field of photocatalysis, with prospective applications in Photoelectrochemical (PEC) solar water splitting.

Exploring the High-Temperature Electrical Performance of Ca3−xLaxCo4O9 Thermoelectric Ceramics for Moderate and Low Substitution Levels

Aliovalent substitutions in Ca3Co4O9 often result in complex effects on the electrical properties and the solubility, and impact of the substituting cation also depends largely on the preparation and processing method. It is also well-known that the monoclinic symmetry of this material’s composite crystal structure allows for a significant hole transfer from the rock salt-type Ca2CoO3 buffer layers to the hexagonal CoO2 ones, increasing the concentration of holes and breaking the electron–hole symmetry from the latter layers. This work explored the relevant effects of relatively low La-for-Ca substitutions, for samples prepared and processed through a conventional ceramic route, chosen for its simplicity. The obtained results show that the actual substitution level does not exceed 0.03 (x < 0.03) in Ca3−xLaxCo4O9 samples with x = 0.01, 0.03, 0.05 and 0.07 and that further introduction of lanthanum results in simultaneous Ca3Co4O9 phase decomposition and secondary Ca3Co2O6 and (La,Ca)CoO3 phase formation. The microstructural effects promoted by this phase evolution have a moderate influence on the electronic transport. The electrical measurements and determined average oxidation state of cobalt at room temperature suggest that the present La substitutions might only have a minor effect on the concentration of charge carriers and/or their mobility. The electrical resistivity values of the Ca3−xLaxCo4O9 samples with x = 0.01, 0.03 and 0.05 were found to be ~1.3 times (or 24%) lower (considering mean values) than those measured for the pristine Ca3Co4O9 samples, while the changes in Seebeck coefficient values were only moderate. The highest power factor value calculated for Ca2.99La0.01Co4O9 (~0.28 mW/K2m at 800 °C) is among the best found in the literature for similar materials. The obtained results suggest that low rare-earth substitutions in the rock salt-type layers can be a promising pathway in designing and improving these p-type thermoelectric oxides, provided by the strong interplay between the mobility of charge carriers and their concentration, capable of breaking the electron–hole symmetry from the conductive layers.

Enhanced thermal stability of hierarchical Y zeolites obtained by acid and subsequent base treatments

Ion exchange and thermal stability of hierarchical Y zeolites obtained by the acid and subsequent base treatments of commercial NaY zeolite were studied. It was found that the resulting hierarchical Y zeolite exhibited lower lanthanum ion exchange efficiency and thermal stability compared to the parent NaY zeolite. The introduction of lanthanum in the hierarchical Y zeolite significantly enhanced its thermal stability due to the advantageous combination of the stabilized effect of lanthanum and the reduced content of residual sodium ions. The latter was of paramount importance because the presence of sodium ions promoted breakdown of the hierarchical Y zeolite framework by dislodging aluminum enriched on the zeolite surface during the base treatment. Notably, the generated mesopores facilitated removal of residual sodium ions during the ammonium ion exchange treatment. Consequently, the hierarchical Y zeolite displayed superior thermal/hydrothermal stability even with a low La loading of 3 w t.%.

Effect of lanthanum doping on water content and diffusion properties of corundum for producing transparent ceramics

The effect of doping corundum with lanthanum on the content of water and other gas impurities, on the diffusion characteristics, on the unit cell size and static strength of fine-crystalline corundum synthesized under thermovapours conditions in a supercritical water fluid was studied.Content, release and diffusion coefficients of water and other volatile impurities in corundum were measured by kinetic thermodesorption mass spectrometry. Water is the main volatile impurity in fine-crystalline corundum. It was found that the introduction of lanthanum into the structure of corundum reduces several times the content of water and other gas-liquid impurities. An increase in the diffusion coefficient of water during the doping of corundum with lanthanum leads to an increase in the degassing rate of fine-crystalline raw materials. When doping corundum, lanthanum, being localized in structural defects, not only displaces structural hydroxyl groups with the formation of strong aluminate-like bonds, but also decreases in the unit cell and increases in the average static strength of the crystals. La-doped corundum, due to the reduced content of water and other gas impurities, is a promising raw material for the production of transparent ceramics.

ThMn12-Type Alloys for Permanent Magnets

Abstract Iron-rich compounds with the tetragonal ThMn12-type structure have the potential to meet current demands for rare-earth-lean permanent magnets with high energy density and operating temperatures of 150–200 °C. However, while it is normal for magnet technology to lag behind the development of underlying magnetic material, this gap has always been unusually large for ThMn12-type magnets. The gap has widened further in recent years, as excellent combinations of intrinsic magnetic properties have been obtained in compounds synthesized with a smaller amount of structure-stabilizing elements (e.g., SmFe11V or Sm0.8Zr0.2Fe9.2Co2.3Ti0.5) or with no such elements (i.e., SmFe9.6Co2.4 thin films). The search for promising compounds continues—with increasing help coming from theoretical calculations. Unfortunately, progress in the development of magnets beyond polymer-bonded interstitially modified powders remains marginal. The introduction of lanthanum (La) was found to stabilize low-melting-temperature minority phases in Sm(Fe,Ti)12 alloys, thus allowing for liquid-phase sintering for the first time. The high reactivity of La, however, has apparently undermined the development of coercivity (Hc). A controlled crystallization of the initially suppressed ThMn12-type phase makes “bulk” magnetic hardening possible, not only in Sm–Fe–V alloys (in which it has been known since the 1990s), but also is in La-added (Ce,Sm)(Fe,Ti)12 alloys. The properties of the bulk-hardened alloys, however, remain unsatisfactory. Mechanochemically synthesized (Sm,Zr)(Fe,Si)12 and (Sm,Zr)(Fe,Co,Ti)12 powders may become suitable for sintering into powerful fully dense magnets, although not before a higher degree of anisotropy in both alloys and a higher Hc in the latter alloy have been developed.

Effect of Lanthanum Doping on the Microstructure, Thermal Stability, and CO2 Adsorption Property of ZIF-8

The reaction materials La(NO3)3·6H2O, Zn(NO3)2·6H2O, and 2-methylimidazole were mixed in a certain proportion. A research process innovatively adopts the parallel flow-drop solvothermal method and a lanthanum-doping method to achieve the synthesis of metal organic frameworks. In this study, we successfully introduce lanthanum into the framework of ZIF-8 to stabilize the spatial structure and improve its performance. The structure and properties of La-ZIF-8 were characterized by the X-ray diffraction (XRD), scanning electron microscope (SEM), thermogravimetry analysis (TGA), and fourier transform infrared spectroscopy (FTIR). The relationship between microstructure stability and macroscopical properties is illustrated. The results show that the doping of lanthanum is beneficial for improving the thermal stability and CO2 adsorption property of ZIF-8 because of the improvement in the microstructure. The introduction of lanthanum to the ZIF-8 is also beneficial for forming porous frameworks and raising the thermal stability and CO2 adsorption properties. The crystallinity, structure, morphology, and thermal stability of La-ZIF-8 are optimal at the La content of 2 atom.%.

Lanthanum enriched aminosilane-grafted mesoporous carbon material for efficient adsorption of tartrazine azo dye

Abstract For the first time the synthesis of mesoporous carbon of cubic structure modified with 3-aminopropyltriethoxysilane and lanthanum chloride, and its ability to remove tartrazine azo dye from aqueous solutions, have been described. The physicochemical properties of the adsorbent were characterized by X-ray diffraction, low-temperature nitrogen sorption, transmission electron microscopy, FT-IR spectroscopy and Boehm titration. The carbon functionalization was found to significantly change its porosity, structure ordering and acid-base character of its surface. The effect of different key parameters such as contact time, temperature, initial concentration and pH of azo dye solution on the effectiveness of tartrazine adsorption was evaluated. Sorption capacity of mesoporous material was found to increase with increasing initial dye concentration and contact time but decreases with increasing temperature of the system, from 25 to 60 °C. The effectiveness of tartrazine removal by La/CKIT-6-A material was compared with that of pristine carbon (CKIT-6) and the aminosilane-grafted sample CKIT-6-A. The introduction of lanthanum on the surface of sample functionalized with 3-aminopropyltriethoxysilane increased its sorption capacity towards tartrazine. The best fit to experimental data was obtained for the Langmuir isotherm model, suggesting homogeneous distribution of adsorption sites on the surface of mesoporous carbon. The adsorption kinetic data were well described with the pseudo-second-order kinetic model. On the basis of the detail analysis of the interactions between the carbon material and tartrazine, a mechanism of dye adsorption was proposed.

Facile synthesis of novel 3D flower-like magnetic La@Fe/C composites from ilmenite for efficient phosphate removal from aqueous solution.

In this study, a novel 3D flower-like La@Fe/C magnetic composite was successfully synthesized by carbothermal reduction of ilmenite via microwave radiation. The physico-chemical properties of the composite were investigated. The results showed that La@Fe/C features a 3D flower-like morphology with an SBET and Vmic of 114 m2 g−1 and 0.017 cm3 g−1, respectively. Zerovalent iron and metal oxides were detected by XRD and XPS on the surface of the adsorbent, which formed as a result of carbothermal reduction of ilmenite using coconut shell-based carbon followed by the introduction of lanthanum. This resultant magnetic La@Fe/C exhibited remarkable phosphate selectivity performance even in the presence of a 50-fold excess of competing ions, which is superior to the pristine ilmenite and coconut activated carbon. Adsorption isotherms and adsorption kinetics fitted well with the Langmuir model and pseudo-second-order model, respectively. A thermodynamic study indicated that the adsorption of phosphate was spontaneous and endothermic. The adsorption–regeneration cyclic experiments of the La@Fe/C composite demonstrated a good level of recyclability. These results indicated that carbothermal reduction of ilmenite followed by the introduction of lanthanum could result in highly efficient and recoverable magnetic particles for the removal of phosphate from wastewater.

Electrodeposition Behavior of Polycrystalline Ni–Mo–La Composite in Alkaline Solution

The polycrystalline Ni–Mo–La composite coating was obtained by electrodeposition through the addition of La3+ ions into Ni, Mo ions main salt weak alkaline solution. The obtained composite contain 0.92 at.% La. According to the law of ionic activity, the redox reaction of three kinds of metal atoms was studied by polarography and cyclic voltammetry. It was found that the addition of lanthanum ions changed the composite structural, phase, and element, and the OH− ions were deduced during the electrodeposition in alkaline solution. The introduction of lanthanum and molybdenum ions negatively shifted the reduction potential of nickel ions and broadened the peaks significantly in the deposition process, retarding the reduction and deposition rate of Ni ions, which was characterized by a multi-step reduction process of Mo and La metal atoms.

Effect of Lanthanum in Zn-La(-Zr)-Si Oxide Compositions on their Activity in the Conversion of Ethanol into 1,3-Butadiene

The introduction of lanthanum into Zn(-Zr)-Si oxide compositions markedly enhances their activity in the conversion of ethanol into 1,3-butadiene. This effect is attributed to the formation of additional basic sites on the catalyst surface.

Oxidative condensation of methane in the presence of modified MnNaW/SiO2 catalysts

The effects of cationic (Ce, Zr, and La) and anionic (S, P, and Cl) admixtures on the activity and physicochemical properties of MnNaW/SiO2 were studied in order to optimize the composition of a catalyst for the oxidative condensation of methane (OCM). It was found that OCM process characteristics can be regulated by varying the type (Ce, Zr, La, S, P, and Cl) and concentration (0.5–5 wt %) of a modifying admixture. For the modified MnNaW/SiO2 catalysts, the yield of the target reaction products increased in the following order of modifying admixtures: S < Zr < P < Ce < La < Cl. The addition of lanthanum, cerium, or phosphorus admixtures insignificantly affected the activity of the MnNaW/SiO2 catalyst, whereas the introduction of sulfur or zirconium led to a decrease in the yield of C2 hydrocarbons. Modification with chlorine improved process characteristics and shifted a maximum yield of C2 hydrocarbons to the low-temperature region. It was established that the introduction of lanthanum considerably improved the stability of catalyst operation. The catalyst composition 2Mn-1.6Na-3.1W-2La/SiO2 was developed to afford a 22% yield of target C2 hydrocarbons at a 54% conversion of methane after a 24-h reaction performed under optimum conditions (reaction temperature, 800°C; reaction mixture flow rate, 117 mL min−1gCat−1 and O2/CH4 molar ratio, 0.5).

Modification of aluminum oxide as a method for controlling its activity and stability in vapor-phase dehydration of glycerol into acrolein

It is shown that promotion of γ-Al2O3 with zirconium, cobalt, boron, lanthanum, and cerium oxides strongly affects its catalytic activity and stability in vapor-phase dehydration of glycerol into acrolein. Modification of gamma-aluminum oxide with acid oxides impairs the stability and activity of the catalyst. Introduction of lanthanum and cerium oxides into the structure of γ-Al2O3 leads to a decrease in the number of strong acid centers, which diminishes the activity of the catalytic system and improves its stability.

Ethanol Gas Sensor Based on Pure and La-Doped Bismuth Vanadate

Bismuth vanadate (BiVO4) and lanthanum-doped bismuth vanadate (La-doped BiVO4) were prepared via the precipitation method. Their films were produced by simple drop-coating of the initial solutions over gold electrodes, which were coated over a glass substrate. The structural properties of BiVO4 and La-doped BiVO4 samples were studied using x-ray diffractometer, diffuse reflectance spectroscopy, scanning electron microscopy, atomic force microscopy, and compositional analysis. A chamber was designed to install the sensing device and also controllable tools for gas flow rate and temperature. Changes in the resistance of the prepared layers were recorded during exposure to various amounts of ethanol vapor at different temperatures. Both BiVO4 and La-doped BiVO4 layers showed measurable responses in the form of resistance drop (increased conductivity). The higher temperatures up to 450 °C led to stronger signals. The layer containing lanthanum showed signals with shorter recovery times. Introduction of lanthanum caused smaller crystallite sizes in addition to the formation of tetragonal phase of BiVO4. Presence of lanthanum increased the amounts of grain boundaries, magnitude of the response, and sensitivity. Sensitivity of La-doped BiVO4 was almost twice that of the BiVO4 at concentrations of 150–500 ppm of ethanol. Also, the correlation of the response as a function of concentration of ethanol in gas phase was exploited, and two different linear ranges were observed for the lower and higher concentrations.

Carbon dioxide reforming of methane for syngas production over La-promoted NiMgAl catalysts derived from hydrotalcites

La-promoted NiMgAl mixed-oxide catalysts derived from hydrotalcite were synthesized by coprecipitation for the carbon dioxide reforming of methane. X-ray diffraction, thermogravimetric analysis, temperature-programmed reduction, X-ray photoelectron spectroscopy, temperature-programmed desorption of carbon dioxide, hydrogen chemisorption and transmission electron microscopy were used to investigate the structure and deactivation characteristics of the catalysts. The catalysts exhibited a narrow Ni-metal particle-size distribution between 5 and 11nm. The presence of lanthanum evidently improved reforming activity in the temperature range of 600–700°C, because the introduction of lanthanum into the NiMgAl catalysts increased the total amount of basic sites and the surface Ni content. The activity of the Ni0.5Mg2.5Al0.9La0.1O4.5 catalyst was slightly higher than those of the other lanthanum-containing catalysts. The addition of lanthanum improved the stability of the NiMgAl catalysts significantly because of the suppression of coke deposition. Lanthanum effectively inhibited coking by increasing the basicity of the catalysts, forming the La2O2CO3 phase and improving nickel metal dispersion.

Oxygen nonstoichiometry and the thermodynamic properties of manganites Ca1 − x − y Sr x La y MnO3 − δ

The content of oxygen in Ca0.6 − ySr0.4LayMnO3 − δ, where y = 0 and 0.05, was determined by coulometric titration over the temperature range 650–950°C at oxygen partial pressure in the gas phase varied from 10−4 to 1 atm. The results were used to calculate the partial molar enthalpy, Δ\( \bar H \)O(δ), and entropy, Δ\( \bar S \)O(δ), of oxygen in manganites. Changes in the Δ\( \bar H \)O(δ) and Δ\( \bar S \)O(δ) dependences caused by the introduction of lanthanum are evidence of the formation of local clusters of the double perovskite type in the Ca0.6Sr0.4MnO3 − δ matrix.

Selective dehydration of bio‐ethanol to ethylene catalyzed by lanthanum‐phosphorous‐modified HZSM‐5: Influence of the fusel

Bio-ethanol dehydration to ethylene is an attractive alternative to oil-based ethylene. The influence of fusel, main byproducts in the fermentation process of bio-ethanol production, on the bio-ethanol dehydration should not be ignored. We studied the catalytic dehydration of bio-ethanol to ethylene over parent and modified HZSM-5 at 250°C, with weight hourly space velocity (WHSV) equal to 2.0/h. The influences of a series of fusel, such as isopropanol, isobutanol and isopentanol, on the ethanol dehydration over the catalysts were investigated. The 0.5%La-2%PHZSM-5 catalyst exhibited higher ethanol conversion (100%), ethylene selectivity (99%), and especially enhanced stability (more than 70 h) than the parent and other modified HZSM-5. We demonstrated that the introduction of lanthanum and phosphorous to HZSM-5 could weaken the negative influence of fusel on the formation of ethylene. The physicochemical properties of the catalysts were characterized by ammonia temperature-programmed desorption (NH(3)-TPD), nitrogen adsorption and thermogravimetry (TG)/differential thermogravimetry (DTG)/differential thermal analysis (DTA) (TG/DTG/DTA) techniques. The results indicated that the introduction of lanthanum and phosphorous to HZSM-5 could inhibit the formation of coking during the ethanol dehydration to ethylene in the presence of fusel. The development of an efficient catalyst is one of the key technologies for the industrialization of bio-ethylene.

Dielectric studies of La and Pb doped SrBi2Nb2O9 ferroelectric ceramic

In this paper, structural and dielectric studies of Sr1−xAxBi2Nb2O9 (A=La, Pb and x=0.2) ceramics are reported. Tetragonal strain decreases on introduction of lanthanum while it increases for the lead doped sample. Addition of lead increases Curie temperature and sample with lanthanum content shows remarkable decrease in Curie temperature with broadened dielectric peak. The sample with x=0.0 shows a rapid fall in dielectric constant value above 100 KHz. The lanthanum and lead doped samples show reduced dielectric loss values with frequency.

The influence of interatomic distances on magnetic ordering in RMnSi compounds (R=La, Y, Sm, and Gd)

Magnetic ordering in the RMnSi (R=La, Y, Sm, and Gd) compounds is investigated. It is found that the type of magnetic ordering depends on the dMn-Mn distance between manganese atoms inside the magnetic layers located in the planes perpendicular to the c axis. This inference is based on the results of studies performed with SmMnSi and GdMnSi compounds in which the distances between manganese atoms are close to the critical value dMn-Mn that corresponds to the crossover between ferromagnetic and antiferromagnetic ordering in RMnSi compounds. The introduction of lanthanum and yttrium atoms into the rare-earth sublattice leads to an increase and a decrease in the unit cell size, respectively, and brings about magnetic phase transitions in the compounds under investigation.

Activity Control by Structural Design of Multicomponent Scheelite-Type Molybdate Catalysts for the Selective Oxidation of Propene

Control of the catalytic selective oxidation of propene to acrolein was achieved by designing multicomponent metal oxide catalysts to have the multifunctions required for the reaction, such as activation of allylic hydrogen of propene, oxygen insertion, reduction–oxidation coupling, lattice oxygen mobility, and activation of molecular oxygen. Scheelite-type Na0.5−3xLa0.5+xMoO4 oxides having lattice oxide ion mobility were chosen as a basic catalytic material and used as a support for bismuth molybdate and cerium oxide loadings. The catalytic activity was primarily controlled by the introduction of lanthanum into the Na0.5−3xLa0.5+xMoO4 lattice, and the selectivity to acrolein was attained separately by loading bismuth molybdates on the surface of the support. It was found that the catalytic activity of Bi2Mo3O12/Na0.5−3xLa0.5+xMoO4 is strongly governed by the value of x irrespective of the loading of Bi2Mo3O12. It was also demonstrated that high activities exceeding the primary activity were achieved by designedly introducing cerium both into the surface bismuth molybdate phase and in the vicinity of the surface of the scheelite support.