Rare Earth Oxides Research Articles

CMAS corrosion resistance of Y2O3–Al2O3 binary ceramic materials

Alumina based rare earth oxides ceramic materials, with the good performance against the CMAS corrosion, were widely used as the thermal/environmental barrier coatings. In this work, three Y2O3–Al2O3 binary ceramic bulks, which were the Y3Al5O12, YAlO3 and Y4Al2O9, were prepared by high temperature solid state reaction using the Y2O3 and Al2O3 as the raw materials. The resistances to CMAS corrosion of these materials at 1250 °C and 1350 °C were compared fully. The compositions and structures of the samples before and after corrosion were analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results showed that the different chemical compositions of the materials resulted in the different optical basicity (OB) values which can decide the reactivity of the material with the CMAS melts. The Y3Al5O12 ceramic material was inert to the CMAS for its low OB value of 0.75 and damaged seriously by the CMAS through physical penetration. The YAlO3 and Y4Al2O9 with the high OB values of 0.80 and 0.87 reacted with the CMAS to form the Ca4Y6(SiO4)6O. The YAlO3 ceramic bulk exhibited the good performance against the CMAS corrosion benefitting from the formation of the Ca4Y6(SiO4)6O and the CaAl2Si2O8.

Improved toughness and oxidation resistance of Nb[sbnd]Si based ultra-high temperature alloys by in-situ generated La2O3 phase

The effects of in-situ rare earth oxide phase La2O3 on the microstructure and properties of NbSi based ultrahigh temperature alloys were investigated. The NbSi based alloys were doped with varying amounts of La (0.05, 0.1, 0.2, 0.4 and 0.8 at.%). The La2O3 phase forms in situ during the melting process. The fracture toughness is greatly improved by the La2O3 phase, and the KQ value of the 0.4La alloy is 27.1% higher than that of the base alloy. The improvement of fracture toughness is due to these three aspects: first, the high-melting-point La2O3 phase (TmLa2O3= 2588 K) precipitates first and effectively refines the microstructure. As a result, the frequency of secondary cracking and crack bridging increases. Second, the formation of the La2O3 phase significantly reduces the issue of oxygen contamination. Third, the high-hardness La2O3 phase separates during the fracture process, reducing the constraints on the deformation of NbSi based alloys. Additionally, La2O3 has the lowest Gibbs free energy among all possible formed oxides. During the oxidation process, the continuous oxidation behavior of the La2O3 phase reduces the degree of oxidation inside the alloy. Therefore, the oxidation resistance is significantly improved.

Effect of different rare earth fluoride doping on microstructure and ablation properties of C/C–ZrC–SiC composites prepared by molten salt assisted reactive melt infiltration

The effect of doping with rare earth elements of different ionic radii on the ablation resistance of C/C–ZrC–SiC composites was investigated and the ablative behavior and ablation resistance of C/C–ZrC–SiC composites with the addition of different rare earth elements was tested. Although rare-earth doped stabilized zirconia has been used for a long time in the field of thermal barrier coatings, the existing techniques are usually coating modifications with rare-earth oxide or boride additions, it is difficult to prepare coatings that can be used on the surface of carbon matrix materials due to the large difference in the coefficients of thermal expansion. Therefore, this study attempts to introduce rare earth components into the interior of C/C–ZrC–SiC composites for matrix modification. The results show that the addition of rare earth elements enhances the ablation performance of the composites, but the mechanism of enhancement is different: rare earth ions with a smaller radius difference from Zr4+ ions stabilize the crystal structure of ZrO2 by forming replacement solid solutions and stabilize the surface oxide film structure by preventing the homogeneous multiphase transformation of the oxide to achieve higher ablation performance; whereas rare earth ions with a larger radius difference from Zr4+ ions cannot stabilize ZrO2 by replacement solid solutions, but instead form high viscosity, low volatility liquid phase oxides to heal the surface defects of the oxide film and reduce liquid phase dissipation to enhance ablation performance.

Formation of yttrium oxalate phase filled by carbon clusters on the surface of yttrium oxide films

In the current paper, we report the results of surface modification of cubic Y2O3 films employing carbon-ion implantation. The characterization results demonstrate the formation of a stable yttrium oxalate-based structure with cavities filled with carbon clusters. Theoretical simulations demonstrate that the incorporation of eighteen-atom carbon clusters into the cavities of Y2(C2O4)3 does not lead to valuable changes in the crystal structure of yttrium oxalate. X-ray diffraction and optical measurements demonstrate that the subsurface bulk area of cubic yttrium oxide remains unperturbed. The oxalate “skin” thickness with embedded carbon clusters is estimated to be approximately 10 nm. The prospective employing the method to manage optical properties and increase the biocompatibility of yttria and lanthanide oxides are discussed.

Broadband ultraviolet photodetector based on rare-earth metal oxide Nd2O3

The detection of ultraviolet (UV) radiation holds significant importance in various fields. As the demand for superior detector performance grows alongside advancements in science and technology, there is a need for detectors with larger light-to-dark rejection ratios and lower standby power consumption. This paper presents the outstanding performance of the rare earth metal oxide Nd2O3 in broadband UV detection. With a wide forbidden band width of 4.6 eV, eliminating the requirement for additional filters, Nd2O3 emerges as an ideal material for broadband UV detectors. The device exhibits remarkable characteristics, including a dark current of only 1.66 × 10−11 A at a 5 V bias voltage, a light-to-dark rejection ratio of 1.33 × 103 at 280 nm and 15 μW cm−2, a responsiveness of 0.061 A W−1, and a detection rate of 4.7 × 1012 Jones. Furthermore, the performance of the device can be significantly enhanced through the formation of a heterojunction with TiO2. The heterojunction device exhibits a shortened response time of 78.64%, a reduced recovery time of 88.97%, and an increased light-to-dark rejection ratio of 2.75 × 103 at a 5 V bias voltage. This significant improvement in performance highlights the potential of the Nd2O3/TiO2 heterojunction in broadband UV detection.

Effects of rare earth oxide additions on the corrosion resistance of TiC-based cermets

TiC-based cermets have inadequate corrosion resistance despite wide use in high-performance applications. Rare earth dopants like Nd2O3 and Yb2O3 aim to improve cermet properties, but their impacts on corrosion are unclear. This work prepared 0.7 wt% Nd2O3- and Yb2O3-doped TiC cermets via vacuum sintering. Experimental results revealed that Nd2O3 doping enhances corrosion resistance by promoting α-FeOOH in corrosion products, while Yb2O3 doping has little effect. First-principles calculations confirmed that Nd promotes α-FeOOH formation. By elucidating contrasting dopant impacts on corrosion, this study provides new insights to guide optimization of rare earth-containing cermet compositions for superior corrosion resistance.

Thermal activation energy on electrical degradation process in BaTiO3 based multilayer ceramic capacitors for lifetime reliability

For a high capacitance and high lifetime reliability of multilayer ceramic capacitors for automotive applications, the activation energy on thermal activation process can typically be calculated by using Arrhenius based Prokopowicz–Vaskas equation as a method for lifetime prediction. In this study, it is clearly observed that the activation energy shows to be constant in the range of ~ 1.5 eV for the prototype MLCCs, higher than the activation energy values of ~ 1.0 eV related to the motion or diffusion of oxygen vacancies reported in the previous literature. The activation energy value of ~ 1.5 eV for three prototype MLCCs is close to a half the energy band gap (Eg/2 ≈ 1.6 eV) of BaTiO3 obtained from specific environment, where oxygen vacancies are stabilized by external containment such as the effect of rare earth oxide additives. Due to an obvious difference in activation energy values, it difficult to explain the conduction mechanism for failure by only oxygen vacancy migration. Therefore, the concepts of electronic processes and oxygen vacancy should be considered together to understand conduction mechanism for failure of BaTiO3-based MLCCs in thermal activation processes. It can be useful as an indicator for future MLCC development with high lifetime reliability.

Magnetic frustration in rare-earth zirconates A2Zr2O7, the case of laser heated pedestal method synthesised A = Er, Tm, Yb, and Lu single crystals

Heavy rare-earth A2Zr2O7 zirconates have been studied for their high application potential, including thermal barrier coating, radiation waste storage, or solid oxide fuel cells. However, previous investigations have focused mostly on the high-temperature properties of polycrystalline samples. The low-temperature properties, important for a full understanding of these materials, remains understudied. We have newly synthesised good-quality single crystals of A2Zr2O7 with A = Er, Tm, Yb, and Lu using the laser heated pedestal method and have characterised them by means of X-ray diffraction, magnetisation, and specific heat measurements. The first three members crystallise in a cubic disordered defect-fluorite structure. Lu2Zr2O7 adopts lower-symmetry rhombohedral structure. Similar magnetic properties of all magnetic zirconates were observed at low temperature. In the unperturbed paramagnetic state, they follow the Curie-Weiss law with an effective magnetic moment close to the respective A3+ free ions. The negative paramagnetic Curie-Weiss temperature, in the case of A = Yb member highly negative, strongly suggests an antiferromagnetic ordering in the compounds. Below 30 K, the magnetic response becomes non-linear in the applied magnetic field, suggesting magnetic correlations between rare-earth moments or/and crystal field effects. Finally, at lowest measured temperature, Er2Zr2O7 and Yb2Zr2O7 members reveal a well-pronounced anomaly in specific heat at 0.9 and 1.5 K, respectively. The specific heat anomaly shifts to higher temperature in an applied magnetic field, suggesting ferromagnetic correlations – in contradiction to the negative Curie-Weiss temperature. We discuss these observations in the framework of freezing of magnetic moments on a disordered geometrically frustrated lattice. In contrast, the low-temperature properties of Tm2Zr2O7 are dictated mostly by its crystal electric field; a crystal-field-singlet ground state which does not provide degrees of freedom for a spin-freezing is proposed. No clear low-temperature anomaly in specific heat is observed down to 0.4 K for the A = Tm member. Lu2Zr2O7 does not bear any magnetic moment, therefore no magnetic signal was observed in any measured data. The results are discussed in the framework of heavy rare-earth A2B2O7 oxides and other magnetically frustrated systems.

A comparative study of 3D printing and sol-gel polymer production techniques: A case study on usage of ABS polymer for radiation shielding

This study focuses on the comparative analysis of ABS polymer samples produced using two distinct manufacturing techniques: 3D printing and the sol-gel methods. In the first approach, ABS polymer was augmented with rare earth oxides, Er2O3 and Gd2O3, in nano powder form and fabricated into test specimens using 3D printing technology. In the second approach, identical samples were prepared via the sol-gel technique involving mold-based fabrication. Elemental content analysis revealed no significant differences between the samples produced by the two methods. The study proceeds to evaluate the gamma-ray shielding, neutron shielding, temperature resistance, and SEM/EDS pictures of ABS samples generated through both techniques. 3D printing method exhibited more favorable results in terms of structure morphology and thermal stability while there is no significant difference for radiation shielding. The results provide insights into the performance and suitability of each production method for radiation shielding applications. This research not only contributes to enhancing radiation shielding technology but also informs the selection of the most appropriate fabrication method for specific applications in nuclear technologies and diagnostic energy range in medical purposes.

Effects of CeO2/Y2O3 rare earth oxides on microstructure and properties of in-situ synthesized WC-reinforced Ni-based cladding layer

A novel tungsten carbide (WC)-reinforced nickel (Ni)-based laser cladding layer was prepared through an in-situ synthesis process. The influence of different concentrations of CeO2/Y2O3 on the microstructure, wear, and corrosion resistance of the in-situ synthesized WC-reinforced Ni-based cladding layer was analyzed. The results revealed that the coatings doped with rare-earth oxides exhibited good micro-hardness (660 HV0.2) and wear resistance when the rare-earth oxide content reached 0.75% CeO2 and 1.50% Y2O3. Additionally, the minimum corrosion rates of the coating were measured at 0.002770 mm/a and 0.0022548 mm/a at 1.5% CeO2 and 1.5 Y2O3 doping, with noble Ecorr values ranging from -0.12549 V to -0.49924 V and lower Icorr values ranging from 2.3550?10-7 A?cm2 to 1.9170?10-7 A?cm2. Furthermore, the wear resistance of the cladding layer was significantly higher than that of the substrate. Both the cladding layer and the substrate exhibited a mixed-wear mode, and they exhibit adhesive wear in wet friction environments.

Sol-gel synthesis of zirconia-based nanoparticles from the side product of tin mining

Indonesia has been one of the world’s primary source of tin since the early of 19th century. Bangka island has the largest tin abundant with a side product is zircon sand (ZrSiO4). The existence of zircon (ZrSiO4) is mostly associated with some of the valuable oxide compounds (VOC) and rare earth oxides (REO). The zirconia powders were synthesized from the zircon sand of PT. Timah Tbk by caustic fusion method followed by sol-gel method. The raw material zircon sand and as-synthesized zirconia were characterized through x-ray fluorescence (XRF), x-ray diffraction (XRD), surface area analysis and porositymeter, thermogravimetric and differential scanning calorimetry analysis (TG-DSC), fourier transform infra-red (FTIR) and scanning electron microscopy (SEM) techniques. The results show that zircon sand from PT Timah Tbk contains some of VOCs, such as ZrSiO4, ZrO2, HfO2, SiO2, Al2O3, TiO2, Fe2O3 and some REOs, such as La2O3, Y2O3, Nb2O5. The fusion temperatures varied from 600 to 800 °C which resulted in an increase of the purity of ZrO2 to 76% based on the XRF analysis. The surface area analysis and porositymeter results showed the significant change in specific surface area, pore size and pore volume of as-synthesized zirconia. The specific surface area increased dramatically from 0.28 m2/g to 173.97, 125.18, and 102.14 m2/g, at fusion temperatures of 600, 700, and 800 °C, respectively. The average particle size of as-synthesized zirconia showed the significant change from 21.31μm to 34.48 nm. The results of this work open new opportunities for the development of zirconia-based nanoparticles from the side product of tin mining.

Research of Bayan Obo tailings characteristics and recovery methods

This paper presents a new method for the recovery of iron and rare earth elements (REEs) from Bayan Obo tailings, which are the waste materials from the extraction of iron and REEs from the Bayan Obo ore deposit in Inner Mongolia, China. The method is based on the combination of microwave-assisted carbothermal reduction and acid leaching. The microwave-assisted carbothermal reduction can effectively reduce the iron oxides and REE oxides in the tailings to metallic iron and REE metals, respectively, and separate them from the gangue minerals. The acid leaching can then dissolve the REE metals from the reduced product and obtain a high-purity REE solution. The effects of various parameters on the performance of the method were investigated and optimized, and the mechanisms and kinetics of the reactions were analyzed and modeled. The results showed that the method can achieve a high recovery rate of iron and REEs, a high selectivity of REEs, a low energy consumption, and a simple process. The economic and environmental benefits of the method are also significant, as it can utilize the Bayan Obo tailings and recover the valuable elements from them, and reduce the waste generation and greenhouse gas emission. The method provides a new and efficient technology for the utilization of Bayan Obo tailings and the recovery of iron and REEs, and contributes to the fundamental understanding of the microwave-assisted carbothermal reduction and acid leaching processes.

Rare earth oxide based electrocatalysts: synthesis, properties and applications.

As an important strategic resource, rare earths (REs) constitute 17 elements in the periodic table, namely 15 lanthanides (Ln) (La-Lu, atomic numbers from 57 to 71), scandium (Sc, atomic number 21) and yttrium (Y, atomic number 39). In the field of catalysis, the localization and incomplete filling of 4f electrons endow REs with unique physical and chemical properties, including rich electronic energy level structures, variable coordination numbers, etc., making them have great potential in electrocatalysis. Among various RE catalytic materials, rare earth oxide (REO)-based electrocatalysts exhibit excellent performances in electrocatalytic reactions due to their simple preparation process and strong structural variability. At the same time, the electronic orbital structure of REs exhibits excellent electron transfer ability, which can reduce the band gap and energy barrier values of rate-determining steps, further accelerating the electron transfer in the electrocatalytic reaction process; however, there is a lack of systematic review of recent advances in REO-based electrocatalysis. This review systematically summarizes the synthesis, properties and applications of REO-based nanocatalysts and discusses their applications in electrocatalysis in detail. It includes the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), hydrogen oxidation reaction (HOR), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO2RR), methanol oxidation reaction (MOR), nitrogen reduction reaction (NRR) and other electrocatalytic reactions and further discusses the catalytic mechanism of REs in the above reactions. This review provides a timely and comprehensive summary of the current progress in the application of RE-based nanomaterials in electrocatalytic reactions and provides reasonable prospects for future electrocatalytic applications of REO-based materials.

Effect of rare earth oxides on the energy storage performance of Sr0.7Bi0.2TiO3 ceramics

In this study, Sr0.7Bi0.2TiO3 (SBT) ceramics doped with Y2O3, Dy2O3 and Gd2O3 rare earth oxides were designed and prepared by the conventional solid-state reaction method. The results show that all ceramics exhibit typical relaxor ferroelectric behavior, and the breakdown strength (BDS) of SBT ceramics is improved. Among them, Sr0.7Bi0.15Y0.05TiO3 ceramics demonstrate excellent energy storage performance, with a high recoverable energy density (Wrec ) of 2.4 J/cm3 and an efficiency (η) of 88.1% under 290 kV/cm. Furthermore, Y2O3-doped SBT ceramics exhibit a rapid discharge speed of 0.05 µs and a high power density (PD ) of 144.1 MW/cm3 under 300 kV/cm in charge-discharge tests. These characteristics have significant potential in pulse power applications.

Raman Broad Scans of Rare Earth Oxide (REO) Glasses from RRUFF Database, Compared to the Raman spectra of RE Oxides from Raman Open Database

Raman Broad Scans of Rare Earth Oxide (REO) Glasses from RRUFF Database, Compared to the Raman spectra of RE Oxides from Raman Open Database

Surface treatments on concrete: an overview on organic, inorganic and nano-based coatings and an outlook about surface modification by rare-earth oxides

Typical coatings incorporate organic groups as carrier of hydrophobicity and polar groups at the solid interface, which are weak points in the interaction with water. In contrast, REOs are shielded from interactions with the environment.

Raman spectroscopic study of anhydrous and hydrous REE phosphates, oxides, and hydroxides.

Rare earth elements (REE) include the lanthanides (La-Lu), Y, and Sc which are critical elements for the green energy transition. The REE show a decrease in ionic radii with increased atomic numbers, which results in a so-called lanthanide contraction systematically affecting crystal structures and mineral properties. Here we present a compilation of reference Raman spectra of ten REE sesquioxides (A-, B- and C-type), five REE hydroxides, eight xenotime-structured REE phosphate endmembers and two solid solutions, seven monazite-structured REE phosphate endmembers and two solid solutions and seven rhabdophane endmembers with up to five Ce1-xLREEx rhabdophane solid solutions (LREE = La-Gd). Raman mode assignment is based on a detailed literature review summarizing existing analytical work and theoretical calculations and systematic trends observed in this study by analyzing different REE-bearing solids. The wavenumbers of the main REE-O Raman band systematically increase with decreasing ionic radii forming discrete linear trends within isostructural mineral groups, that can be used to estimate the REE-O mode in other solids with known REE-O coordination numbers. Photoluminescence using 266 nm, 532 nm and 633 nm excitation laser wavelengths for REE-bearing oxides, hydroxides, anhydrous and hydrous phosphates is also presented providing a new framework for identifying REE-phases in phosphate-bearing natural mineral deposits.

Optimization of safe doping level for enhanced CO2 flux in composite membrane

Rare earth doped oxides have been intensively promoted for the last two decades to embrace the high-performance target of a ceramic–carbonate composite CO2-separation membrane, with countless incidents of exsolution.

Improved photocatalytic efficiency of rare earth metal-incorporated magnesium oxide nano-hexagonal sheets for the degradation of Ciprofloxacin and Methylene Blue dye under visible light irradiation

Researchers worldwide are working hard to develop nanoparticles that can be used for the photocatalytic degradation of dangerous substances and antibiotics. In this report, we present a study on how to make yttrium-incorporated magnesium oxide nanoparticles using hydrothermal and calcination methods. These particles measure around 50 nm and have excellent photocatalytic properties. We analyzed them using various physiochemical techniques like X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy with EDAX, transmission electron microscopy, X-ray photoelectron spectroscopy, and ultra-violet diffused reflectance spectroscopy. The nanohexagons created in this study showed reduced band gap energy from 4.8 eV to 3.8 eV when yttrium was incorporated into MgO nanohexagons resulting in an unusual increase in light absorption within the visible light region. Experimental reports show these synthesized nanoparticles could degrade about 66.5 % antibiotic Ciprofloxacin (CIP) and 79 % Methylene Blue (MB) dye respectively with .O2– playing a significant role at every step during the degradation process. This study demonstrates that these synthesized nanohexagons have practical applications as promising photocatalysts for treating toxic contaminants found in industrial effluents.

Recent advances in electrochemical recovery of rare earth elements from NdFeB magnets

Recent advances in electrochemical methods promise a more sustainable recycling of rare earth elements (REEs) from discarded NdFeB permanent magnets. The demand for NdFeB magnets for clean energy applications is rapidly increasing, motivating recycling efforts to diversify REE supply. The main electrochemical steps include the selective dissolution of REE-rich phases at the anode and the reduction of REE ions at the cathode. Pretreatment with demagnetization, mechanical size reduction, and leaching contributes to the release and concentration of REEs. Thermal demagnetization and mechanical crushing make the magnets brittle and improve the penetration of leaching agents. Acid leaching dissolves the REEs, but also dissolves the iron. To facilitate the extraction of REEs at high temperatures, molten salt electrolytes such as chlorides are used, while ionic liquids allow extraction under milder conditions, but with the caveat of possible decomposition during the process. Aqueous solutions have been most thoroughly investigated due to their versatility and affordability. Fluoride-based molten salt electrolytes effectively dissolve RREs and provide a stable environment for hightemperature electrodeposition, improving the efficiency and sustainability of rare earth element recovery. To isolate highpurity REE oxides and metals, additional processing is required using techniques such as solvent extraction, selective precipitation, and electroseparation. Key factors for optimal electrochemical recycling are maximizing selectivity for REEs, minimizing energy consumption and waste generation, and simplifying integration. Although technical challenges remain, recent advances show that electrochemical technologies can improve the sustainability of recycling critical REEs from permanent magnets.