Rare Earth Oxides Research Articles

Influence of crystalline phase structure of rare earth oxides on active oxygen and basic sites

Herein, the effects of crystalline phase structures of rare earth oxides on active oxygen and basic sites were investigated. The fluorite structure shows the best lattice oxygen mobility and redox properties due to its open structure and weakest Ln-O bond strength. For Pr6O11 and Tb4O7, the presence of polyvalent cation states further enhances these properties. Based on the basicity and number of basic sites, the surfaces of A-type, B-type, and C-type lanthanide sesquioxides facilitate the generation of chemisorbed oxygen species in the following order: A-type >B-type >C-type. Furthermore, the basicity and amount of chemisorbed oxygen species are dependent on the electronegativity of rare earth elements, which decreases gradually from La to Lu. In rare earth oxides, electrons are less biased toward oxygen, the basicity of lattice oxygen decreases, and fewer electrons are produced for gaseous oxygen activation and chemisorbed oxygen generation.

Plasmon-enhanced NIR-II photoluminescence of rare-earth oxide nanoprobes for high-sensitivity optical temperature sensing.

With ongoing advancements in photothermal therapy, achieving efficient tumor cell eradication while minimizing damage to healthy tissues necessitates a highly effective and non-invasive real-time temperature monitoring technique for human tissues. Herein, we report a near-infrared (NIR)-II optical temperature sensing nanoprobe featuring rare-earth-doped gadolinium oxide nanocrystals (RENCs) attached to the dumbbell mesoporous silica-coated gold nanorods (AuNRs). The composite nanoprobe presents an intense absorption in the NIR region, and NIR-II photoluminescence (PL) increases by 97.2 to 102-fold compared to pure RENCs upon 980 nm irradiation. The localized electric field generated through surface plasmon resonance effects of AuNRs demonstrated a dumbbell-shaped distribution that aligns with the structure of nanoprobes, maximizing the PL enhancement of RENCs. Moreover, the NIR-II emissions are changed with the rising temperature, with an exceptional relative sensitivity of 7.25% K-1 at 338 K based on PL lifetime, indicating the nanoprobe is highly potential for optical temperature sensing.

Manufacturing the current flow diverter architecture in REBCO tapes using silver inkjet printing

Abstract A low normal zone propagation velocity (NZPV) combined with critical current inhomogeneities favor the nucleation of destructive hot spots in rare-earth barium copper oxide (REBCO) tapes. Increasing the NZPV using the current flow diverter (CFD) concept is a promising solution to mitigate the risk of developing hot spots. The fabrication method of CFD REBCO tapes implies several steps consisting in masking, silver etching, mask removal, and silver deposition, which takes time and remains a barrier to the implementation of a low-cost industrial production of long-length CFD REBCO tapes. This work presents a cost-effective and maskless CFD fabrication approach that relies on inkjet printing (IJP) of silver patterns directly on top of the REBCO layer to create a non-uniform interfacial resistance between the silver and the REBCO surface, along the width of the tape. The parameters of IJP and oxygen annealing were optimized to obtain highly conductive silver patterns deposited on the surface of the REBCO layer. CFD REBCO tapes were successfully fabricated using commercial REBCO tapes and the proposed method without degrading the superconducting properties. Experimental measurements revealed an increase of the NZPV by a factor of 6-7 compared to commercial REBCO tapes.

Influence of different rare earth oxides on CNC ultrasonic machining of HP-HVOLF sprayed ceramics coating

The current study aimed at the optimization of process parameters for microchannel fabrication on thermal sprayed carbide coatings using rotary ultrasonic machining (RUSM). Rare earth oxides (REOs) such as La₂O₃, CeO₂, and Er₂O₃ have been incorporated into WC-Co-Cr coatings to enhance machinability and improve coating characteristics. The research has demonstrated that La₂O₃ doped coatings have significantly increased the material removal rate (MRR), with a 15 % improvement when compared to undoped coatings. Additionally, surface roughness has been reduced by 20 %, resulting in a smoother and more uniform finish. The inclusion of REOs has refined the microstructure of the coatings, yielding denser and more compact layers, which has reduced defects and improved the overall surface quality. Furthermore, the hardness of the coatings has been enhanced by 45 %, with La₂O₃ doped coatings achieving a maximum hardness value of 1313 ± 11 HV. The findings have highlighted the potential of REO doping to enhance the performance and efficiency of microchannel fabrication on WC-Co-Cr coatings using RUSM, contributing valuable insights to industrial applications.

Preparation and Electrochemical Performance of Alkaline Earth Metal-Doped Nd2Ce2O7 Proton Conductor Hydrogen Separation Membranes

Nd2Ce2O7 is a rare earth oxide with a fluorite structure and exhibits proton conductivity. Alkaline earth metals (Mg, Ca, Sr, Ba) doped Nd2Ce2O7 powders were synthesized using the citrate sol-gel method. The doped samples retain the fluorite structure, and enhanced oxygen vacancy concentration. Notably, Nd1.85Mg0.15Ce2O7-δ exhibited the highest oxygen vacancy concentration, reaching an electrical conductivity of 2.91×10-2 S•cm-1 in a humid atmosphere of 20%H2 and 80%N2 at 900°C. Hydrogen separation membranes were fabricated using alkaline earth metal-doped Nd2Ce2O7 as the proton-conducting phase and Pt as the electron-conducting phase. The results indicated that Pt-Nd1.85Mg0.15Ce2O7-δ had the optimal hydrogen permeation flux, reaching 8.35×10-9 mol•cm-2•s-1 at 900°C. It demonstrated short-term stability in environments containing CO2 and H2O, and an increase in temperature and hydrogen partial pressure on the feed side enhanced hydrogen permeation, highlighting its potential as a hydrogen separation membrane material.

Assessment of toxicity and oxidative stress induced by rare earth oxide nanoparticles in brine shrimp (Artemia salina)

This study meticulously explored the oxidative stress effects induced by lanthanum (III) oxide (La2O3), erbium (III) oxide (Er2O3), and yttrium (III) oxide (Y2O3) nanoparticles on Artemia salina, with the objective of evaluating the environmental toxicity of rare earth oxide nanoparticles. The characterization of the nanoparticles was conducted using a suite of advanced techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential analysis. Artemia salina, a widely recognized model organism in ecotoxicological research, was exposed to these nanoparticles under meticulously controlled laboratory conditions. The investigation focused on quantifying oxidative stress markers, such as reduced glutathione (GSH), malondialdehyde (MDA), and antioxidant enzymes including catalase (CAT), superoxide dismutase (SOD), and glutathione-S-transferase (GST). The findings revealed significant alterations in these biomarkers, indicating nanoparticle-induced oxidative stress, which varied according to the type of nanoparticle and the duration of exposure.

Effect of Pr6O11 rare-earth oxide on the structural characteristics and optical parameters of polyvinyl alcohol film

Effect of Pr6O11 rare-earth oxide on the structural characteristics and optical parameters of polyvinyl alcohol film

Effect of rare earth oxide (Pr4O7) second phase and fine grain on the corrosion behavior of Ti-0.3Mo-0.8Ni

The effect of grain refinement and second phase (Pr4O7) on the corrosion mechanism of the Ti-0.3Mo-0.8Ni was studied. The Pr4O7 nanophases are distributed in the α/β phase boundaries and the β phases (Pr ≤ 0.5 wt. %). Most of the Pr4O7 phases are distributed at the boundaries (Pr ≥ 1 wt. %). The Pr element refines the primary β grains. With the increment of Pr content, the passivation film becomes more stable, denser and thicker, which prolongs the decrease time of OCP, increases the corrosion potential and reduces the corrosion tendency. After the passivation film ruptures, the Pr4O7 aggravates the galvanic corrosion.

Surface Engineering via Rare Earth Oxide Composite Coating to Enhance the High-Voltage Stability of the LiCoO2 Cathode.

The commercial application of high-voltage LiCoO2 (LCO) faces significant challenges due to rapid capacity decay, primarily attributed to an unstable interface and structure at deeply delithiated states. Herein, a unique rare earth oxide composite coating comprising La2O3, Y2O3, and LaYO3 has been prepared to stabilize LCO at high voltage. The synergistic effect between these rare earth oxides significantly reinforces the protective capabilities of the coating, effectively enhancing the interfacial/structural stability of LCO. When tested at 4.6 V, the coated LCO exhibits an excellent capacity retention of 94.4% after 300 cycles at 1 C. Even after an ultralong charge/discharge test of 700 cycles at 2 C, the coated LCO retains 85.2% of its initial specific capacity, which significantly outperforms the uncoated LCO (6.3%). Moreover, the coated LCO shows enhanced cycling performance at a high temperature of 45 °C, owing to the outstanding thermal stability of the La-Y-O composite. Additionally, the superior cycling stability of the coated LCO at 4.7 V, compared to the uncoated LCO, demonstrated the promising potential of the La-Y-O composite coating in improving electrochemical performance of LCO at higher cutoff voltages. These findings highlight an efficacious strategy to enhance the interfacial/structural stability of high-voltage LCO using rare earth oxides.

Physicochemical reaction-based allocation for the resource consumption of hydrometallurgical processing of rare-earth oxides—a case study on ion adsorption-type rare-earth oxides in China

Physicochemical reaction-based allocation for the resource consumption of hydrometallurgical processing of rare-earth oxides—a case study on ion adsorption-type rare-earth oxides in China

Nanomaterials for enhanced X‐ray‐triggered cancer therapy: Progress and prospects

AbstractX‐rays, a form of ionizing radiation with high energy and significant penetration capability, are commonly used in clinical tumor treatment through radiotherapy. Despite their widespread use, optimizing X‐ray efficacy remains a critical challenge due to issues such as radiation resistance and damage to surrounding health tissues. Recent advancements in nanotechnology have introduced new opportunities and challenges in cancer diagnosis and treatment. This review summarizes the latest progress in nanomaterials for X‐ray‐triggered cancer therapy, highlighting their various advantages such as targeted delivery, reduced side effects, and enhanced therapeutic efficacy. We examine how nanomaterials, including metals, metal oxides, metal sulfides, metal fluorides, rare earth oxides, cluster compounds, metal‐organic frameworks, and nanohybrids, enhance the effectiveness of X‐ray‐triggered treatments. Furthermore, we address the current challenges and future prospects of efficient X‐ray‐triggered cancer therapy, aiming to provide a comprehensive overview for researchers and clinicians in the field.

Cold Molecular Ions via Autoionization below the Dissociation Limit.

Several diatomic transition metal oxides, rare-earth metal oxides, and fluorides have the unusual property that their bond dissociation energy is larger than their ionization energy. In these molecules, bound levels above the ionization energy can be populated via strong, resonant transitions from the ground state. The only relevant decay channel of these levels is autoionization; predissociation is energetically not possible and radiative decay is many orders of magnitude slower. Starting from translationally cold neutral molecules, translationally cold molecular ions can thus be produced with very high efficiency. By populating bound levels just above the ionization energy, internally cold molecular ions, exclusively occupying the lowest rotational level, are produced. This is experimentally shown here for the dysprosium monoxide molecule DyO, for which the lowest bond dissociation energy is determined to be 0.0831(6)eV above the ionization energy.

Effect of carbon-supported rare earth oxide catalysts on the microstructure, hydrogen storage kinetics, and thermodynamics of Mg-La-Ni alloys

In this study, using an improved chemical vapor deposition carbonization method, Eu2O3@C, PrO1.83@C, and La2O3@C composite catalysts were successfully synthesized and incorporated into Mg96La3Ni alloys via ball milling. These catalysts significantly enhanced the hydrogen storage properties of the alloys, particularly in terms of hydrogenation kinetics. Among the catalysts, PrO1.83@C demonstrated the most significant improvement. At 360 °C, the Mg96La3Ni alloy containing 3 wt% PrO1.83@C achieved a 75.1 % hydrogenation saturation ratio within 2 min and released 3 wt% H2 in 3.1 min. While the catalysts did not significantly alter the alloy's thermodynamics, they substantially reduced the dehydrogenation activation energy. The addition of 3 wt% Eu2O3@C, PrO1.83@C, and La2O3@C lowered the activation energy barriers to 116.6, 101.4, and 114.8 kJ/mol H2, respectively, compared to 121.67 kJ/mol H2 for the pristine Mg96La3Ni alloy. This enhancement is attributed to the synergistic effects of the "hydrogen pump" mechanism of rare earth hydrides and the abundant active sites provided by the carbon component, which collectively promote faster hydrogen diffusion and nucleation reactions.

Characterization of Heavy Minerals and Their Possible Sources in Quaternary Alluvial and Beach Sediments by an Integration of Microanalytical Data and Spectroscopy (FTIR, Raman and UV-Vis)

Quaternary stream sediments and beach black sand in north-western Saudi Arabia (namely Wadi Thalbah, Wadi Haramil and Wadi Al Miyah) are characterized by the enrichment of heavy minerals. Concentrates of the heavy minerals in two size fractions (63–125 μm and 125–250 μm) are considered as potential sources of “strategic” accessory minerals. A combination of mineralogical, geochemical and spectroscopic data of opaque and non-opaque minerals is utilized as clues for provenance. ThO2 (up to 17.46 wt%) is correlated with UO2 (up to 7.18 wt%), indicating a possible uranothorite solid solution in zircon. Hafnoan zircon (3.6–5.75 wt% HfO2) is a provenance indicator that indicates a granitic source, mostly highly fractionated granite. In addition, monazite characterizes the same felsic provenance with rare-earth element oxides (La, Ce, Nd and Sm amounting) up to 67.88 wt%. These contents of radionuclides and rare-earth elements assigned the investigated zircon and monazite as “strategic” minerals. In the bulk black sand, V2O5 (up to 0.36 wt%) and ZrO2 (0.57 wt%) are correlated with percentages of magnetite and zircon. Skeletal or star-shaped Ti-magnetite is derived from the basaltic flows. Mn-bearing ilmenite, with up to 5.5 wt% MnO, is derived from the metasediments. The Fourier-transform infrared transmittance (FTIR) spectra indicate lattice vibrational modes of non-opaque silicate heavy minerals, e.g., amphiboles. In addition, the FTIR spectra show O-H vibrational stretching that is related to magnetite and Fe-oxyhydroxides, particularly in the magnetic fraction. Raman data indicate a Verwey transition in the spectrum of magnetite, which is partially replaced by possible ferrite/wüstite during the measurements. The Raman shifts at 223 cm−1 and 460 cm−1 indicate O-Ti-O symmetric stretching vibration and asymmetric stretching vibration of Fe-O bonding in the FeO6 octahedra, respectively. The ultraviolet-visible-near infrared (UV-Vis-NIR) spectra confirm the dominance of ferric iron (Fe3+) as well as some Si4+ transitions of magnetite (226 and 280 nm) in the opaque-rich fractions. Non-opaque heavy silicates such as hornblende and ferrohornblende are responsible for the 192 nm intensity band.

Hydrogen-based mineral phase transformation of bastnaesite: Detailed assessment of physicochemical properties and flotation behavior

Iron-bearing rare earth ores are valuable mineral resources, and the hydrogen-based mineral phase transformation (HMPT) process has significant development potential. In this study, the changes in physicochemical properties and flotation behavior of bastnaesites subjected to HMPT were investigated. The results show that bastnaesite decomposed slowly below 600 °C, but increased roasting temperature and time enhanced the decomposition, resulting in a roasted product with over 85 % rare earth oxide (REO) grade. HMPT also increased the initial pH of the flotation pulp from about 7.5 to 11.0 and increased La and Ce ion concentrations. By increasing the dosage of SHA, flotation recoveries comparable to the raw ore can be achieved. The HMPT process converted bastnaesite to REOF, which formed complex phases such as Ce7O12 and REF3 when exposed to air. This process resulted in significant damage to the particle structure, increased porosity, reduced geometric particle size, and improved wettability. After HMPT, Ce on the particle surface existed predominantly as Ce4+, which formed Ce(OH)4 precipitation during flotation, inhibiting SHA adsorption. The increased particle porosity facilitated deeper SHA penetration and greater adsorption, resulting in higher SHA dosage compared to the raw ore.

Construction of heterojunction based on Nd2S3 and tin dioxide for rapid detection of ethanol

The gas-sensing properties of Nd2S3 have not been previously explored. In this study, a novel composite material comprising rare-earth metal sulfide (Nd2S3) and metal oxide (SnO2) was successfully prepared using a two-step hydrothermal method for the rapid detection of ethanol. Characterization results revealed that the morphology and specific surface area of Nd2S3-SnO2 remained largely unchanged after composite formation. However, the built-in electric field established between Nd2S3 and SnO2 significantly enhanced carrier transport and separation. Additionally, the introduction of extra oxygen vacancies increased the content of chemisorbed oxygen, providing more active sites for ethanol molecules, thereby improving the gas-sensing performance. The Nd2S3-SnO2 sensor demonstrated extremely high detection accuracy (R2=0.9965) over the 20–300 ppm ethanol concentration range, with response/recovery time of 8/274 s at 100 ppm ethanol concentration and response value of 93. It also possesses excellent selectivity to ethanol, long-term stability and reversibility. This work represents a preliminary exploration of the gas-sensing properties of Nd2S3 and its underlying mechanisms through the construction of a heterojunction structure between metal sulfide and metal oxide.

Effect of Er2O3 and Y2O3 on microstructure and mechanical properties of Ti2AlNb alloy

Rare earth oxides can significantly refine the microstructure of the cast alloys and improve their mechanical properties. In this study, Er2O3 and Y2O3 particles were chosen to add into the Ti2AlNb-based alloy with vacuum non-consumable arc melting method. For the Er2O3 particles, it has obvious dissolution and re-precipitation characteristics during melting. While for the Y2O3 particles, they are more stable, and aggregated and grew up during melting. These two kinds of Er2O3 or Y2O3 both have obvious refinement effects on the B2 grains due to their heterogeneous nucleation. Specially, adding Er2O3 particles can promote the decomposition of the B2 and α2 phases and the increases of the O-phase content. But adding the Y2O3 particles can inhibits the B2 decomposition and just only promotes the α2 decomposition into the O-phase. Additionally, the TAC-Er2O3 ingot shows the worst mechanical properties at room-temperature due to its large size and grain boundary segregation of the Er2O3 reinforcements. Conversely, the TAC-Y2O3 alloy exhibits excellent strength and ductility whatever at room- and high- temperatures owing to its fine grain strengthening and effective strengthening of the second precipitated Y2O3 phases.

Tribological and Corrosion Properties of Al2O3@Y2O3-Reinforced Ni60A Composite Coatings Deposited Using Laser Cladding

Since rare earth oxides and hard ceramic particles improve coating quality, a novel Al2O3@Y2O3 core–shell structure was prepared. Then, Ni60A coatings with different amounts (2~6 wt.%) of Al2O3@Y2O3 core–shell structures were prepared using laser cladding technology on an H13 steel surface. To demonstrate the unique effect of the core–shell structure on the performance of the coatings, a set of controlled experiments was also conducted with different proportions of Al2O3-Y2O3 mechanically mixed powders. The effect of Al2O3@Y2O3 addition on the phase composition, element distribution, microstructure, wear, and corrosion resistance of the coatings was characterized and tested thoroughly. By comparing the forming quality, hardness, wear, and corrosion resistance of the different coatings, 2 wt.% was confirmed as the optimal concentration of Al2O3@Y2O3, and its corresponding friction coefficient was about 0.44. The wear rate was approximately 4.15 × 10−3 mm3·(N·m)−1, the self-corrosion potential was around −0.3659 V, and the self-corrosion current density was about 1.248 × 10−6 A·cm−2.

Rare earth-doped ZrB2-MoSi2 ceramics: Densification and oxidation behavior

The effect of rare earth oxides (REO), Nd2O3 and Eu2O3, on the densification and oxidation behavior of pressureless sintered ZrB2-MoSi2 ceramic composites was investigated. Addition of REO results in the formation of REO-silicates which are liquid at the sintering temperature and contribute to matter transfer mechanisms. Oxidation studies at 1500 °C for 0.5–4 h evidenced that Eu2O3 can improve oxidation resistance in the ZrB2-MoSi2 system, especially after prolonged exposition, whilst Nd2O3 induces faster degradation of the ceramic. It was found that the Eu dispersed both in silica and in zirconia modifies the rheological properties of the glassy phase thus playing an important role in hindering oxygen inward from the atmosphere to the subsurface, resulting in a noticeable improvement of the oxidation resistance.

Synergism of h-BN and La2O3 in improving the tribological performance of Al2O3 coatings

Wear is a significant cause of material loss, contributing to surface degradation of crucial components, notably within engineering sectors. This article is dedicated to enhancing tribological properties through the implementation of Al2O3-based ceramic coatings, specifically targeting situations where reciprocating sliding wear predominates. This study introduces lanthanum oxide (La2O3), a rare earth oxide, as a reinforcing material in Al2O3 coatings in varying weight percentages of 1.2%, 1.6%, and 1.8% respectively along with 3% hexagonal boron nitride (h-BN). The coatings were developed by the high-velocity oxy-fuel (HVOF) surface modification technique, with SS304 serving as the substrate. The porosity, hardness, and chemical composition of the developed coatings were examined. Additionally, reciprocating tribological testing of the coatings was conducted at two loads (5 N and 15 N) under dry sliding conditions. Results indicated that coating containing 95.4% Al2O3–3% h-BN–1.6% La2O3 reduced the porosity up to 50% and improved hardness by 46% compared to the 97% Al2O3–3% h-BN coating. The formation of the α-Al2O3 phase leads to an increase in coating hardness and a reduction in porosity. Notably, the coating comprising 97% Al2O3–3% h-BN exhibited the lowest coefficient of friction among all developed coatings under both loads. Furthermore, an increase in load led to a decrease in the coefficient of friction for all developed coatings. Furthermore, the addition of La2O3 (1.6 wt%) to the coating with 3 wt% h-BN exhibited the lowest wear at both loads. The findings also revealed increased wear at high loads for all developed coatings. SEM, EDS, and XRD analysis of the worn surfaces revealed the contribution of h-BN and La2O3 in enhancing friction behavior through the formation of oxides such as α-Al2O3, B2O3, Al8B2O15, and Al11La0.497O17, along with alterations in wear mechanism and the size of wear debris. The composite coatings developed in this study shall be helpful in advanced engineering applications.