Oxide La2O3 Research Articles

Holmium doped La2O3 and its composite with graphitic carbon nitride for the removal of atrazine and chlorpyrifos from wastewater

Herein, the co-precipitation method was employed for the synthesis of rare earth metal oxide La2O3, Holmium doped La2O3, and its composite with 2D layered material i.e. graphitic carbon nitride (g-C3N4) to study their photocatalytic behavior towards organic pollutants. Pollutants employed to study are pesticides that include atrazine and chlorpyrifos. Structural, spectral, morphological, and elemental analysis were done by XRD, FTIR, SEM, and EDX respectively. Optical bandgap calculations showed the decrease in band edge positions of the bare La2O3 from 5.02 eV to 3.39 eV by doping of Ho in La2O3 lattice. The photocatalytic degradation efficiency of prepared samples was evaluated using a dual beam UV-Visible spectrophotometer. Experimental investigation showed that the prepared composite i.e. Ho doped La2O3 @g-CN had remarkable photodegradation activity of about 60 % and 86 % towards the atrazine and chlorpyrifos respectively. While the pristine La2O3 showed only 41 % and 65 % degradation activity and Ho doped La2O3 showed 52 % and 75 % removal efficiency for atrazine and chlorpyrifos respectively by using 0.03 g/100 mL of photocatalysts under solar light exposure of about 80 min. The enhanced degradation activity of composite (g-C3N4/Ho@La2O3) as compared to its other counter parts is due to its increased surface area and more active sites provided by g-C3N4 for electrons trapping to cause a delay in electron-hole pair recombination rate. The enhanced surface area also played a key role in adsorbing more pollutant molecules for degradation.

Analyzing the synergistic effects of hard ceramic TiB2 and rare earth oxide La2O3 on mechanical behaviour, wear resistance, and residual stress of AA6061-T6 hybrid composite fabricated via ultrasonic-assisted stir casting

This investigation involves the fabrication of an aluminium metal matrix composite using AA6061-T6 alloy as the matrix, incorporating 2 wt% of hard ceramic (TiB2, 14 μm particle size) and 0.5 wt% of rare earth oxide (La2O3, 40–50 nm particle size) reinforcement powders through ultrasonic assisted stir casting. The study examines the microstructure, residual stress, and mechanical properties alongside performing pin-on-disk wear tests. Taguchi's optimization and ANOVA are used to optimize the wear rate of the composite using three control parameters: Load, Sliding Distance, and Sliding Speed. Results from optical micrography and field emission scanning electron microscopy (FESEM) with energy-dispersive spectrometer (EDS) analysis confirm the uniform distribution of TiB2 and La2O3 particles within the AA6061-T6 volume when ultrasonic stirring is employed. The composite's microhardness is found to increase by 25.15 %, and its tensile strength by 31.32 % compared to the base alloy due to a higher dislocation density. ANOVA highlights Load as the primary influencer, contributing 69.54 %, followed by Sliding Distance (17.45 %) and Sliding Speed (12.56 %). The optimal parameters for minimizing wear rate are found to be Load (20 N), Sliding Distance (1500 m), and Sliding Speed (2.5 m/s). Scanning Electron Microscope (SEM) images of worn surfaces reveal various mechanisms such as abrasion, delamination, and adhesion, with abrasion being the dominant mechanism. Residual stress increases with the addition of TiB2 and La2O3 particles in the matrix, showing transitions from tensile to compressive stress from the inner to the outer surface of the composite casting.

Density functional model of threshold voltage shifts at High-K/Metal gates

A density functional analysis of oxide dipole layers used to set the threshold voltages in high-K/metal CMOS gate stacks is given in terms of the band alignments and chemical trends of these component oxide layers. The oxides SrO, La2O3, HfO2 and Al2O3 are found to have similar band gaps and form a ‘staircase’ of band alignments, allowing them to shift the metal electrode Fermi level in both n-type and p-type directions. This analysis supersedes previous largely empirical models based on metal oxide ion densities or electronegativity scales.

Effect of La2O3 on hardness, wear resistance and corrosion resistance of WC/Fe90 iron-based composite coatings

In this paper, WC/Fe90 iron-based composite coatings were prepared using plasma spraying technology. The influence of rare earth oxide La2O3 on the microstructure and properties of the composite coatings was studied through microstructural characterization, phase identification, microhardness, wear resistance, and corrosion resistance. The results showed that the composite coatings were mainly composed of α-Fe, M7C3, Fe-Cr, FexCy, and other reinforcing phases. The addition of La2O3 promoted the decomposition of WC particles and improved the uniformity of the coatings. When the La2O3 content reached 1.0 wt%, the hardness was the highest, reaching 885.481 HV, which was 10% higher than that of the untreated coatings. The addition of La2O3 increased the friction coefficient but still improved the wear resistance. Compared to the coatings without La2O3, the mass loss due to wear was reduced by approximately 40%. Moreover, the addition of La2O3 formed a passive film on the surface of the coatings, effectively preventing the penetration of Cl- ions and refining the grain structure of the coatings, significantly enhancing the corrosion resistance. When the La2O3 content was 1.0 wt%, the corrosion resistance of the coatings was the best.

Magnetic properties of Sr1.5La0.5FeMoO6-δ depending on the phase composition of the reaction mixture

This paper presents investigations of phase transformations during the crystallization of Sr1.5La0.5FeMoO6-δ by the solid-phase technique from a stoichiometric mixture of oxides MoO3, La2O3 and Fe2O3 and SrCO3 and precursors Sr0.5La0.5FeO3 and SrMoO4. Using XRD and thermogravimetric analyses, the influence of synthesis modes on the chemical processes occurring during the formation of double perovskite was studied. It has been established that the synthesis of lanthanum-strontium ferromolybdate in a mixture of oxides proceeds through a number of series-parallel stages. At the initial stage of interaction, the resulting lanthanum-strontium ferromolybdate is enriched with iron and its composition changes during the reaction towards an increase in the molybdenum content. As the temperature increases, the content of double perovskite increases, and the concentration of the secondary phase SrMoO4 does not disappear to zero until the synthesis temperature, which indicates that solid-phase reactions with the formation of a solid solution Sr1.5La0.5FeMoO6-δ from oxides are difficult to occur. It was determined that to minimize the influence of intermediate reaction products it is necessary to use precursors Sr0.5La0.5FeO3 and SrMoO4. Based on the results of studying the temperature dependences of the degree of phase transformations during the crystallization of double perovskite, combined heating modes were optimized. The use of optimized synthesis modes made it possible to obtain single-phase Sr1.5La0.5FeMoO6-δ powder with the superstructural ordering (82%), the Curie temperature of 450 K and a magnetization value of 40.9 A · m2 · kg-1 at T = 77 K in a magnetic field with induction B ≥ 0.86 T.

Study on the Effect of Rare Earth Oxide Addition on the Microstructure and Properties of Ni60/WC-Ni Coatings Prepared by Laser Cladding

Rare earth oxides have been proven for their ability to refine grains and have high melting points. In this paper, different contents of rare earth oxide La2O3 were added into the Ni60/WC-Ni composite coating, in order to study its effect on the coating properties. SEM observation confirmed that the grain was refined significantly after the addition of La2O3. Energy Dispersive Spectroscopy (EDS) was applied to investigate the composition and X-Ray Diffraction (XRD) was used to measure the residual stress in the coating samples. In addition, the microhardness and wear resistance of the samples were tested. The results showed that the dilution ratio of coatings with different additions of La2O3 was in the range of 2.4 to 9.8%, and the sample with 1.0% addition of La2O3 exhibited the highest hardness of 66.1 HRC and best wear resistance with a wear volume of 9.87 × 106 μm3, and the residual stress increased from 159.4 MPa to 291.0 MPa. This implies that the performance of the coating has been obviously improved after the addition of La2O3.

Wet gravity separation and froth floatation techniques for rare earth elements beneficiation from monazite ore in Jordan

The demand for extracting Rare Earth Elements (REEs) from their deposits is growing significantly around the world since they are essential in many mature and growing industries. This study investigated the elemental and mineralogical composition of a Bulk sample and its potential for rare earth elements (REEs) beneficiation through Wet Gravity Separation (WGS) and Froth Floatation (FF) processes. Results obtained from WDXRF analysis showed that Si, Hf, Ti, Fe and Zr were the major elements present in the Bulk sample, with SiO2 accounting for 64.79 wt%. The TREOs concentration was around 0.90 wt%, dominated by Ce, La, and Nd, with other REEs present in smaller concentrations. XRD analysis indicated that Quartz was the major mineral present in the Bulk sample. WGS and FF were then used to beneficiate the oxides CeO2, La2O3, Nd2O3, Pr6O11, Y2O3, Gd2O3, and Sm2O3. Results showed significant concentration increases of these elements in the WGS concentrate, with high grade and good recoveries achieved for Ce, La, and Nd. Overall, the study provides insights into the potential of WGS and FF as a beneficiation technique for REEs in monazite ore.

MODIFICATION OF LANTHANUM OXIDE La<sub>2</sub>O<sub>3</sub> ON THE STRUCTURE OF SUPRASTRUCTURAL UNITS IN ALKALI BORATS

It shows a significant change in structurally sensitive properties in the experiment of modifying a melt (or glass) of the B2O3–Na2O system with lanthanum oxide La2O3 with the destruction of superstructural units when lanthanum atoms hit, since small additions of rare earth metal oxides lead to a significant change in the properties of alkali borate melts. Molecular models of some of the superstructural units, the structure and properties of which were calculated by semi-empirical quantum chemical methods with MNDO and PM7 parameters: as a result of the optimization procedure, both methods lead to models that are qualitatively close, but differ in bond lengths, and practically the same value of heat of formation. The superstructural unit of the considered type is preserved, while its characteristics change: the volume occupied by it increases, the newly formed bond is less strong and its ionic degree is greater.

Effect of rare earth oxide doping on microstructure and mechanical property of Mo-30 W solid solution alloy

Oxide dispersion-strengthened (ODS) molybdenum‑tungsten (MoW) alloys are ideal materials for plasma-facing components of fusion reactors. In this paper, the effects of rare earth oxides (RExOy) Y2O3, CeO2 and La2O3 on the sintering behavior, microstructural and mechanical properties of MoW solid solution alloys were investigated. The initial alloy powders were produced by spray drying combined with the two-step reduction method (composed of carbothermal reduction and deep hydrogen reduction steps), and the solid solution alloy with good mechanical properties was prepared by subsequent sintering. The results showed that the doping of rare earth oxides suppressed the grain growth of MoW alloy, and thus improved the mechanical properties. Compared with CeO2 and Y2O3, the doping of La2O3 is more favorable to obtain dense and fine-grained MoW solid-solution alloys. The doping of La2O3 produced a larger Zener force and interfacial drag force, which effectively hindered the grain boundary migration and refined the grains. The microhardness and bending strength of Mo-30 W-1La2O3 alloy reached the maximum values of 557 HV and 771 MPa.

Mechanistic Insight into La2O3 Dopants with High Chemical Stability on Li3PS4 Sulfide Electrolyte for Lithium Metal Batteries

Unlike the unstable liquid-state organic electrolyte at high temperatures, the solid-state electrolytes with high safety have attracted a broad prospect for the development of all-solid-state lithium metal battery (ASSLMB). Among the solid electrolytes, the sulfide-based electrolyte with low grain boundary resistances is one of the most practical choices due to its high lithium-ionic conductivity. The introduction of non-conducting oxide fillers into sulfide matrix is an effective way to increase their ionic conductivities and interfacial stabilities with the electrodes of battery simultaneously. Unfortunately, the acting mechanism of non-conducting oxide dopants with high chemical stability on the sulfide electrolyte has not been elucidated clearly. In this work, the rare-earth oxide La2O3 with high chemical stability was selected as a doping component of Li3PS4 sulfide electrolyte for the first time. The experimental results show that a certain amount of La2O3 can not only increase the ionic conductivity of Li3PS4 electrolyte, but also enhance their interfacial stability with the electrodes effectively. The XPS analytical results reveal the enhanced stability of Li3PS4 electrolyte with La2O3 doping due to the formation of SEI film on the lithium anode. Both the static and dynamic simulations illustrate that La2O3 particles inside the Li3PS4 electrolyte could facilitate the migration of Li+ ion by way of the “space-charge effect.”

Microstructure and tribological performance of boride layers on ductile cast iron under dry sliding conditions

Stamping die is prone to wear failure due to mechanical friction. In this work, high-hardness boride layers were obtained on ductile cast iron as stamping die, by a boronizing process at 800–950 ℃ for 2–6 h with the addition of rare-earth oxide La2O3. A sawtooth-like morphology of the boride layer was observed using scanning electron microscopy (SEM). The greatest boride layer micro-hardness of the boride layers of 1648 HV0.1 was obtained at 900 ℃ and 6 h with 4% La2O3, and X-ray diffraction (XRD) analysis showed that the boride layers were a component of Fe2B as adding La2O3. The tribological tests showed that the wear resistance of the boride layers was enhanced with increasing boronizing temperature and time, where the ductile cast iron substrate corresponding to 900 ℃ and 6 h exhibited the best wear resistance. Compared with that of the boride layer without La2O3, the thickness and wear resistance of the boride layer with 4% La2O3 was increased by 37.2% and 31%, respectively. The thickness of the boride with 6% La2O3 decreased by 27.6%, and the wear rate was highest, indicating that excessive La2O3 inhibited the enhancement effect. The wear mechanism of the boride layers transformed from mild adhesive wear to fatigue spalling as the normal load and sliding speed increased.

Hybrid La2O3-cPVP Dielectric for Organic Thin Film Transistor Applications

In this work, we have studied the electrical performance of cross-linked polyvinyl phenol (cPVP) modified lanthanum oxide (La2O3) bilayer dielectric film in pentacene thin film transistors (TFT). A simple spin-coating and room temperature operated cross-linking reaction of the hydroxyl moieties of PVP and the nitrogen groups of PMF were carried out to form the cross-linked PVP. The deposition of a thin 30 nm cPVP layer over the La2O3 layer provided a low leakage current (<10−7 A cm−2), causing a reduction in the interface trap density. Besides, the modified surface properties of the La2O3 layer were favorable for the growth of pentacene organic semiconductors. As a result, the current on-off ratio and the sub-threshold slope was improved from 104 and 1.0 V/decade to 105 and 0.67 V/decade. The La2O3∕cPVP pentacene TFT operated at −10 V also exhibited improvement in the field-effect mobility to 0.71 cm2 Vs−1 from 0.48 cm2 Vs−1 for the single-layer La2O3 (130 nm) device. Thus, our work demonstrates that the rare earth oxide La2O3 with cPVP is an excellent dielectric system in the context of emerging transistors with hybrid polymer gate dielectrics.

In English

X-ray phase and thermogravimetric analysis, scanning electron microscopy and energy-dispersion spectroscopy were used to study the products of phase formation during the precipitation of lanthanum and cerium salts in the presence of silver nitrate and recipients of precipitators, nucleating agents and hydrolysis regulators. Thermogravimetric analysis shows the completion of the La(OH)3 lattice dehydroxylation process at a temperature of ~ 300 °С and probable destruction of sulfates at a temperature of ~ 340 °С. The phase interaction of lanthanum oxide(III) with silver ends at T ~ 400 °C. The DTG curve shows a two-stage weight loss, which characterizes the destruction of lanthanum and silver hydroxides (250 °C) and the removal of sulfates (~ 340 °C), respectively. According to the TG, the total weight loss is 21.6 %. For the cerium-containing system the only endothermic effect of dehydroxylation of cerium hydroxide at T = 250 °C with its conversion into cerium dioxide is observed. The destruction of nitrates (anionic component of solutions) takes place at the temperature of 400 °C. Weight loss takes place at T = 150 °C and is 53.9 %. Thus, on the basis of TG-DTA data, it can be assumed that the formation of composites particles based on lanthanum and cerium oxides, modified with silver, ends at the temperature of 400 °C. The X-ray diffraction data shows that at the initial stage the system undergoes the formation of cerium and lanthanum hydroxides, and during lyophilization of the precipitate (T = 160 °C) the crystal lattice of hydroxides partial dehydroxylation takes place with the formation of trigonal oxides La2O3 and Ce2O3. It has been found that the presence of silver cations in the solution can affect the phase composition of lyophilized structures and the formation of the CeO2 phase. It is shown that the hydroxylamine chloride injection into the system can initiate the silver restoration on the lanthanum oxide surface and also partially restore it to the LaO phase. Temperature treatment of the samples (T = 400 °С) promotes homogenization of the precipitate composition: formation of 30 nm cerium dioxide particles with silver clusters evenly distributed on its surface, and hexagonal lanthanum oxide plates with individual silver particles as the second phase. In three-component systems, two modifications of lanthanum oxides (trigonal and cubic), cerium dioxide and metallic silver are formed. It is found that the chemical composition of the precipitates contains the main elements – La, Ce, O, Ag and impurity – S or Cl, as the anionic component of the initial solutions, N and K in the composition of the initial suspension. It is shown that the morphology of the samples is represented by hexagonal structures of lanthanum hydroxide and oxide, spherical and pseudocubic particles of cerium dioxide and lanthanum oxide, spherical clusters of silver.

LaFeO3 perovskite nanoparticles for efficient capture of elemental mercury from coal-fired flue gas

LaFeO3 perovskite was synthesized by sol–gel method and calcination method and used to remove mercury in flue gas. Three kinds of metal oxides La2O3, Fe2O3, and LaFeO3 were evaluated. The results indicated that the performances for Hg0 removal decreased in the order of LaFeO3 > Fe2O3 > La2O3. LaFeO3 has ∼94% removal efficiency at 120 ℃. To explore the temperature response range and the influence of simulated flue gas, the performance of LaFeO3 to remove Hg0 under O2, NO, SO2, and different temperature conditions was further examined. Furthermore, LaFeO3 is repeat-ability. The characterization results showed that the Hg0 transition to HgO is due to the valence change of iron and the release of lattice oxygen. In addition, density functional theory (DFT) was conducted to calculate the density of states to verify the performance of the sample. This work shows that LaFeO3 is a promising adsorbent for mercury removal from flue gas in coal-fired power plants.

Synthesis and Characterization of Lanthanum Oxide La2O3 Net-like Nanoparticles By New Combustion Method

Herein is a new procedure to synthesize lanthanum oxide (La2O3) nanoparticles, which is eco-friendly and simple. The La2O3 nanoparticles were prepared by sol-gel method using modification in time of stirring, type of PEG, and temperature of the reaction. Scherer's formula was used to estimate the average crystallite of La2O3 nanoparticle size from X-ray diffraction peaks of powder. The measured average particle size of La2O3 nanoparticles using the major signals of the X-ray diffraction spectrum after calcination was 37 nm. Fourier Transform Infrared Spectroscopy technique was done to analyze the chemical structure of synthesized materials. The surface morphology of obtained nanoparticles was also studied by SEM and AFM techniques. Thermal gravimetric analysis was investigated by Thermogravimetric analysis (TGA) to confirm the thermal stability of synthesized nanoparticles.

Structural and electrical properties of pure and doped lanthanum oxide

In this communication, structural and electrical properties of rare earth oxides La2O3 (LO) and LaNdO3 (LNO) have been studied. To understand the structural properties of the LO and LNO samples, X-ray diffraction (XRD) measurement was carried out at room temperature. The XRD patterns have been analyzed by Rietveld refinement to confirm the single-phase nature of both the samples. The crystal structures of studied samples were created from the derived parameters of Rietveld parameters. The crystal size and lattice strain have been estimated using Williamson–Hall (W–H) plot analysis. Frequency-dependent dielectric constant and loss tangent have been studied for a frequency range of 20 Hz to 2 MHz. To estimate the relaxation time and contribution of the charge carriers in the studied samples, relaxation mechanism and universal dielectric response (UDR) model have been employed. The ac conductivity measurements were carried out for the same frequency range (i.e., 20 Hz to 2 MHz) which has been understood on the basis of Jonscher’s power law. The barrier height has been calculated by fitting the power law. Frequency-dependent impedance behavior has been discussed in the context of grains and grain boundaries for both the samples under study.

La4Te7O20: A new ternary rare-earth metal(III) oxotellurate(IV) with isolated [TeO3]2– and [Te3O8]4– anions

The new rare-earth metal(III) oxotellurate(IV) La4Te7O20 was obtained as a single-crystalline by-product of the La2Te3O9 synthesis through a solid-state reaction of the corresponding binary oxides La2O3 and TeO2. The colorless, lath-shaped crystals of La4Te7O20 crystallize in the monoclinic space group C2/c with the lattice parameters a ​= ​2740.63(16) pm, b ​= ​580.92(3) pm, c ​= ​1326.71(8) pm and β ​= ​106.849(3)° for Z ​= ​4. The structure consists of two crystallographically distinct lanthanum-oxygen polyhedra with the coordination numbers of seven plus one and eight (d(La3+–O2–) ​= ​241 – 262 pm plus 310 pm). These lanthanum-oxygen polyhedra are attached to one ψeq1-trigonal [TeO4]4– bipyramid (d(Te4+–O2–) ​= ​186 – 214 pm, ​2× each) and three different ψ1-[TeO3]2– tetrahedra (d(Te4+–O2–) ​= ​184 – 189 pm) with twice the frequency of occurrence. So the central [TeO4]4– core is linked with two [TeO3]2– groups via common oxygen vertices to form an isolated [Te3O8]4– anion, leading to the structural formula La4[Te3O8][TeO3]4. The presence of all these different oxotellurate(IV) units is confirmed by a single-crystal Raman spectrum.

The Effect of Electrochemical Composite Coatings with LaF3-LaB6 Particles in Nickel-Copper Matrix on the Metallurgical Processes in Arc Welding of Low Alloy Ferrite-Pearlite Steels.

Development of welding consumables with fluorides and borides of rare earth metals is a promising area for improving the weldability of low alloy steels. As lanthanum fluoride and boride dissociate, lanthanum and boron dissolve in the weld pool and the welding arc plasma is saturated with fluorine. As a result of FeO, MnO, SiO2 deoxidation and FeS, MnS desulfurization, refractory lanthanum sulfides and oxides La2O3, La2S3 are formed in the weld pool, which can be the crystallization nuclei in the weld pool and the origin of acicular ferrite nucleation. The paper proposes a model of metallurgical processes in the arc and weld pool, as well as a model of electrochemical adsorption of Ni2+ cations in colloidal electrolytes during electrostatic deposition of nano-dispersed insoluble particles of LaF3 or LaB6 on the surface of wire. The paper discusses the constructional design of the welding wire and the technology for forming electrochemical composite coatings with copper and nickel matrix. The composite wires applied in the welding of low alloy steels make it possible to refine the microstructure, increase the tensile strength by 4% and the impact toughness of welds by 20%.

Theoretical study of the oxygen adsorption energy for the supported Pt cluster, focused on the electronic metal-support interaction

This study analyzed the icosahedral Pt55 cluster on the surface of La2O3 by density functional theory (DFT) calculations. The oxygen adsorption energy (ΔE) for the supported Pt55 cluster was different from the ΔE value for the Pt55 cluster without oxide supports. Moreover, the ΔE values for the supported Pt55 cluster depend on adsorption sites. This study applied the idea of Electronic Metal-Support Interaction (EMSI), and proposed the concept of “effective chemical potential (μeff)”. According to DFT calculation, the μeff values of supported Pt55 cluster were the intermediate values between the chemical potential values of Pt55 without oxide support (μPt55) and La2O3 (μLa2O3) (i.e. μPt55<μeff<μLa2O3). Finally, this study proposes a method to predict ΔE values for the supported Pt cluster. The ΔE value can be estimated by substituting predicted μeff value into a mathematical formula that combines the Hard-Soft-Acid-Base (HSAB) concept and d-band center theory. The proposed method requires μPt55, μLa2O3 and d-band center values of the Pt55 cluster without oxide support, but do not require any DFT results of the supported Pt55 cluster. Comprehensibly, the proposed method can predict ΔE values from basic physical quantities.

Oxygen annealed ZnO–La2O3 TFTs fabricated using CBD technique

Cost-effective chemical bath deposition (CBD) technique have been utilized to fabricate ZnO thin films on ultrasonically cleaned glass substrates and successfully applied as channel layer in thin film transistors (TFTs). The deposited films are characterized by XRD and SEM analysis. High -k rare earth oxide La2O3 is used as gate dielectric. The ZnO films are annealed at ambient and oxygen atmosphere at 500°C for one hour. The I-V characteristics of the TFTs are studied and various electrical parameters such as field effect mobility, threshold voltage, sub-threshold swing, drain current ON/OFF ratio and transconductance are evaluated.