Rare Earth Materials Research Articles

Two 3D Rare-Earth Double Perovskite Materials Constructed with a Pair of Enantiomers.

Organic-inorganic hybrid chiral small-molecule materials combine the inherent properties of both components; however, studies integrating chirality with rare-earth double-perovskite materials are limited. In this work, we synthesized two enantiomers of three-dimensional (3D) hybrid rare-earth double-perovskites, [R-3-HDMP]2CsEu(NO3)6 (1) and [S-3-HDMP]2CsEu(NO3)6 (2), by reacting R-3-HDMP and S-3-HDMP (where 3-HDMP = 3-hydroxy-N,N-dimethylpyrrole) with CsNO3 and Eu(NO3)3 in a 2:1:1 ratio within an acidic solution. Both R-3-HDMPI and S-3-HDMPI crystallize in the chiral space group P212121 at room temperature, exhibiting a transition from SHG-on to SHG-off (SHG = second harmonic generation) upon heating and cooling. The temperature-dependent X-ray single-crystal diffraction analysis carried out on compound 1 and compound 2, before and after the phase transition, disclosed the transformation of their space groups from noncentrosymmetric to centrosymmetric. Additionally, the incorporation of rare-earth elements as hybrid B-site cations imparts exceptional fluorescence properties to the compounds. These materials effectively merge the unique characteristics of chiral molecules with the exceptional luminescence of double-perovskite structures, paving the way for innovative optical devices and advanced information processing technologies.

Six Sigma-Based Mathematical Optimization Framework for Flux-Switching Machines: A Roadmap for Quality, Performance, and Manufacturing Tolerances

Flux-switching wound field machines (FSWFMs) offer high torque density and independence from rare-earth materials, making them promising candidates for sustainable electric vehicles and industrial applications. However, their adoption is limited by challenges such as high torque ripple, efficiency variations, and sensitivity to manufacturing tolerances. This study presents a Design for Six Sigma (DFSS) optimization framework that integrates sensitivity analysis, response surface modeling (RSM), and multi-objective genetic algorithms to address these challenges. The optimized solution reduces torque ripple by 7.69%, improves torque output, and enhances energy efficiency. By incorporating Six Sigma principles, the framework ensures robust performance under manufacturing variations, bridging the gap between theoretical optimization and practical implementation. This scalable and efficient methodology establishes FSWFMs as viable solutions for industrial applications, revolutionizing electric machine design.

Scalable Synthesis of 2D ErOCl with Sub-meV Narrow Emissions at Telecom Band.

Van der Waals (vdWs) materials are promising candidates for hetero-integration with silicon photonics toward miniaturization and integration. VdWs materials like molybdenum telluride and black phosphorus, despite being prominent, exhibit air sensitivity, and their room temperature emissions can be significantly broadened by tens of meV. Here, a self-encapsulation strategy is developed to scalably synthesize robust 2D vdWs ErOCl with sub-meV narrow emissions at the telecom C-band. Diverse 2D rare earth materials are also grown via chemical vapor deposition (TmOCl, YbOCl, HoOCl, DyOCl, SmOCl, NdOCl, TbOCl, GdOCl, EuOCl, and PrOCl), demonstrating the strategy's generalizability. The as-grown ErOCl exhibits high crystalline quality and excellent ambientand thermal stability (300°C). Photoluminescence analysis reveals a series of narrow emissions across the visible to near-infrared spectrum. The ErOCl's emission at the telecom band is narrowest among 2D luminescent materials, and suitable for integrating with photonic chips. Temperature-dependent photoluminescence spectra facilitate the understanding of emission mechanisms, analyzed using a crystal field perturbation model. Moreover, these emissions can be tuned by external magnetic fields. This research not only pioneers a novel strategy for synthesizing 2D rare earth materials but also paves the way for innovative building blocks in the realm of on-chip optical communications.

Enhanced magnetocaloric effect in rare-earth aluminum-based magnetic materials for hydrogen liquefaction

Enhanced magnetocaloric effect in rare-earth aluminum-based magnetic materials for hydrogen liquefaction

Frustrated Magnetism and Spin Anisotropy in a Buckled Square Net YbTaO4.

The interplay between quantum effects from magnetic frustration, low-dimensionality, spin-orbit coupling, and crystal electric field in rare-earth materials leads to nontrivial ground states with unusual magnetic excitations. Here, we investigate YbTaO4, which hosts a buckled square net of Yb3+ ions with Jeff = 1/2 moments. The observed Curie-Weiss temperature is about -1 K, implying an antiferromagnetic coupling between the Yb3+ moments. The heat capacity shows no long-range ordering down to 0.10 K, instead shows a field-dependent broad maximum indicative of short-range correlations. The magnetic entropy recovered and magnetization measurements confirm a spin-orbit driven Jeff = 1/2 Kramers doublet ground state. Point charge calculations show that the Yb3+ ions do not host the quintessential XY spin anisotropy observed in typical Yb-based quantum magnets like NaYbO2, YbMgGaO4, and pyrochlores but rather exhibit an almond-shaped anisotropy with an easy axis. Thus, YbTaO4 can serve as a model system to study frustrated magnetism in a square lattice using the J1-J2 Heisenberg model. This work also emphasizes the significance of small perturbations to the local crystal electric field that can alter the spin anisotropy and change the collective behavior of the system.

Efficient Separation of Adjacent Rare Earths in One Step by Using Ion‐microporous Metal–Organic Frameworks

AbstractHigh‐purity rare earth (REEs) materials are key raw materials for the development of cutting‐edge technologies. However, due to similar physical and chemical properties, separating adjacent REEs from actual samples faces a formidable challenge. To overcome this challenge, an ion‐microporous metal–organic framework (ATZ‐BTC‐Zn; MOFs) is designed and synthesized, featuring densely packed nano‐trap pockets constructed from non‐coordinating carboxyl and amino groups. The synergistic effect of open nano‐trap pockets and suitable ions channel in ATZ‐BTC‐Zn is highly responsive to the size variation of lighter REEs. Notably, the configuration of Zn(H2O)62+ counterion in ATZ‐BTC‐Zn is similar to lanthanide hydrated ions (Ln(H2O)63+), facilitating the efficient ion exchange between them in the high‐speed ion transport channel. This accelerates the diffusion of REEs within the MOF pores, enhancing the utilization of active adsorption sites and promoting the efficient capture of adjacent REEs by nano‐traps. The binary model experiments show high separation factors for adjacent REEs (SFLa/Nd = 908, SFCe/La = 543), demonstrating efficient separation by ATZ‐BTC‐Zn in one step. This capability achieves the selective separation of adjacent REEs in tailings wastewater, providing a strategy to infer the compatibility between MOFs and REEs.

Computational Imaging Encryption with Steganography and Lanthanide Luminescent Materials

AbstractOptical encryption is a potential scheme for information security that exploits abundant degrees of freedom of light to encode information. However, conventional encryption based on fluorescent materials faces challenges in handling complex secret information. Alternatively, single‐pixel imaging (SPI) provides a computational modality to solve these problems. In this study, a high‐capacity fluorescence encryption scheme, achieved by introducing lanthanide materials and steganography into the encoding and decoding processes of SPI is proposed. Two types of well‐designed lanthanide luminescent materials are utilized and excited to generate fluorescence images (fluo‐images), which are crucial in this scheme. Various practical experiments using fluo‐images as secret keys demonstrate the robustness, effectiveness, and repeatability of this scheme. Furthermore, multi‐image experiments indicate the potential of this method to increase secret information capacity. Thus, the proposed fluorescence encryption scheme does provide an efficient computational encryption strategy based on lanthanide luminescent materials for information security, which can improve the security of traditional optical encryption and simultaneously enhance the flexibility of SPI computational decryption.

The high electron mobility for spin-down channel of two-dimensional spin-polarized half-metallic ferromagnetic EuSi2N4 monolayer.

The two-dimensional (2D) monolayer material MoSi2N4 was successfully synthesized in 2020[Hong et al., Science 369, 670, (2020)], exhibiting a plethora of new phenomena and unusual properties, with good stability at room temperature. However, MA2Z4 family monolayer materials involve primarily transition metal substitutions for M atoms. In order to address the research gap on lanthanide and actinide MA2Z4 materials, this work conducts electronic structure calculations on novel 2D MSi2N4 (M = La, Eu) monolayer materials by employing first-principles methods and CASTEP. High carrier mobility is discovered in the indirect bandgap semiconductor 2D LaSi2N4 monolayer (~5400 cm2 V-1 s-1) and in the spin (spin-down channel) carrier mobility of the half-metallic ferromagnetic EuSi2N4 monolayer (~2800 cm2 V-1 s-1). EuSi2N4 monolayer supplements research on spin carrier mobility in half-metallic ferromagnetic monolayer materials at room temperature and possesses a magnetic moment of 5 μB, which should not be underestimated. Furthermore, due to the unique electronic band structure of EuSi2N4 monolayer (with the spin-up channel exhibiting metallic properties and the spin-down channel exhibiting semiconductor properties), it demonstrates a 100% spin polarization rate, presenting significant potential applications in fields such as magnetic storage, magnetic sensing, and spintronics.

Scalable Fabrication of Flexible Thermoelectric Generator with Non-Toxic Ga:ZnO and PEDOT:PSS Thermoelements for Wearable Energy Harvesting

This study presents a lightweight, flexible thermoelectric generator (TEG) designed for sustainable energy harvesting in wearable electronics. The TEG integrates p-type PEDOT:PSS and n-type Ga:ZnO thermoelements, utilizing scalable drop-casting and 3D-printing techniques to address key concerns of sustainability, scalability, and safety. Unlike conventional TEGs that rely on toxic or rare-earth materials, this device employs predominantly earth-abundant, non-toxic components, offering a more cost-effective and environmentally friendly alternative. Structural analysis using FE-SEM and EDX revealed a relatively dense microstructure with uniform elemental distribution in the free-standing thermoelements, contributing to the device’s mechanical flexibility and performance stability. The TEG, consisting of five thermoelement pairs, achieved a peak open-circuit voltage of 0.111mV and a power output of 0.123 nW at a temperature difference (ΔT) of 10K, demonstrating performance competitive with TEGs fabricated using more complex and expensive methods. When tested on a human wrist, the TEG generated 0.230 nW at a ΔT of 17K, outperforming other wearable TEGs, with power increases observed during body movement. Additionally, the device maintained stable resistance at a 90° bending angle, enhancing its ability to conform to the body’s shape for improved energy harvesting and efficiency. While the power output can be further improved, this TEG represents a notable advancement in flexibility, scalability, and the use of eco-friendly, cost-effective materials and fabrication methods. Addressing these critical challenges in wearable thermoelectrics paves the way for future self-powered health monitoring, fitness tracking, and environmental sensing applications.

Design of high-entropy rare-earth disilicate materials for thermal environmental barrier coatings through thermal-mechanical experiments and finite element simulation studies

Design of high-entropy rare-earth disilicate materials for thermal environmental barrier coatings through thermal-mechanical experiments and finite element simulation studies

Regulation strategy of preparation methods for new spherical La-Y-Ni hydrogen storage alloy with ultra-long cycle lives

La-Y-Ni-based alloys are high-performance superlattice rare-earth H2-storage electrode materials. However, their complex phase structural evolution results in poor electrochemical cycle lives. In this study, a gas atomization method develops to obtain spherical La-Y-Ni-based hydrogen storage alloys with high structural stability. The spherical La-Y-Ni powder exhibits a narrow particle size distribution between 30 and 75 μm and capacity retention over 60 % for 600 cycles. A three-dimensional particle insertion strain model and finite element simulations reveal the direct effects of the particle morphology on the stress distribution during hydrogen embedding. The spherical powder exhibits a uniform strain, good mechanical properties, and resistance against pulverization and damage. The new preparation strategy for spherical powders prominently regulates the [A2B4] subunit, decreasing the subunit mismatch and lattice strain, and improving the structural stability during the hydrogen absorption/desorption. In addition, the morphology regulation, phase composition controllability, platform characteristics and electrochemical properties investigate by comparing the use of gas atomization, casting, and rapid quenching. This study provides a new direction for developing high-performance spherical electrode materials.

NdCoO3 nanoparticles grown on reduced graphene oxide sheets as an efficient electrocatalyst for hydrogen evolution reaction

To meet the huge energy crisis due to the limitation of fossil fuel, hydrogen has been considered the most promising clean energy source due to its high efficiency, non-toxic, and clean emission products. Therefore, over the past few years, researchers have been trying to find an effective route for bulk production of hydrogen energy from water splitting. Many efforts have already been made to use suitable electrocatalysts such as transition metal-based oxides, hydroxide alloys, and carbides for hydrogen production from water splitting but these electrocatalysts are hindered due to instability over prolonged usages in alkaline solution. To overcome this issue, rare-earth perovskite oxide materials are being focussed as an efficient electrocatalyst for electrocatalytic hydrogen evolution reaction (HER) through water splitting in an alkaline medium. In the present work, we have explored to synthesize the rare-earth perovskite neodymium cobalt oxide (NdCoO3) nanoparticles grown on reduced graphene oxide (rGO) sheet, via a hydrothermal route for electrochemical hydrogen evolution in an alkaline medium. The NdCoO3/rGO nanocomposite shows a remarkably low overpotential of 84mV at the desired current density of 10 mA/cm2, compared to pristine NdCoO3 and rGO. The synergistic impact between NdCoO3 and the rGO backbone, resulting in enhanced efficiency in the HER. The nanocomposite also shows high stability and durability even more than 100 h of electrolysis under an inert atmosphere.

Environmental impacts of electric motor technologies: Life cycle approach based on EuP Eco-Report

The industrial sector's need for efficient electric motors is paramount for both energy conservation and climate change mitigation. This study evaluates the environmental impacts of three motor technologies—Squirrel Cage Induction Motors (SCIM) at IE3, Synchronous Reluctance Motors (SynRM), and Permanent Magnet Synchronous Motors (PMSM) at IE5—using a life cycle assessment (LCA) approach with the EuP Eco-Report tool. The focus is on 11 kW, 4-pole motors, representing typical industrial applications. Results show that IE5 SynRMs and PMSMs offer significantly higher operational efficiency, with PMSMs reaching 95 % efficiency compared to 92.7 % for SCIMs. However, the environmental trade-offs are notable: SynRMs require 156.9 kg of materials, including 80.5 kg of electrical steel, while PMSMs demand 1.8 kg of rare earth materials, contributing to higher manufacturing impacts. Total energy consumption over 15 years in the operational phase reveals a consumption of 3.88 TJ for SCIM, 3.83 TJ for SynRM, and 3.79 TJ for PMSM, indicating substantial savings from higher efficiency motors. Despite their efficiency, PMSMs exhibit higher impacts in water use (1172 l in manufacturing) and heavy metal emissions, primarily due to challenges in recycling rare earth components. This analysis highlights the environmental cost-benefit trade-offs between improving operational efficiency and managing the resource-intense production of higher-efficiency motors. As electric motor technology evolves, careful consideration of life cycle impacts, especially in manufacturing and end-of-life phases, is essential to achieve sustainable energy solutions.

Swapping conventional doping with novel white light emission from La2O3: clitoria ternatea extract

The common flower Clitoria ternatea is gifted with organic dyes anthocyanin delphinidin and betalains betacyanin that exhibit broad emission peaks centered at 490 nm and 630 nm. These fresh emission bands in the blue-green and red regions make it a potential white light source that can swap the conventional rare-earth doped phosphor materials. By this line, the extract shows decent emission in its solution state. However, the emission intensity reduces rapidly after a while, owing to the high decay rate of organic dyes in their pure form. Thus, the floral extract is combined with the antioxidant La2O3, reducing the luminescence decay to a noticeable value. The complex formation does not alter the innate La2O3 crystal structure, identified by the XRD peaks, but aids with near-white emission. Upon complex formation, the optical band gap of the host La2O3 falls to the semiconductor range, from 5.1 eV to 2.5 eV. White light emission from La2O3: Clitoria ternatea complex is studied for different extract concentrations and heating conditions, and deemed as a potential replacement for conventional rare-earth doping.

Interplay of Chinese rare earth elements supply and European clean energy transition: A geopolitical context analysis

The European clean energy sector sources approximately 98 % of its rare earth materials from China. We examine Chinese rare earth supply's effect on European renewable energy, particularly solar and wind sectors from 1990 to 2020. Using the gravity model, we find a positive correlation between China's rare earth supply and European solar energy during bullish markets. A similar response is seen in wind energy during bearish markets, considering global and China-specific geopolitical risks. We also observe a negative correlation between China's economic growth and mineral supply to Europe, with European income growth having no significant impact. Additionally, multiplicative economic growth negatively impacts Chinese mineral supply. The study also reveals a positive link between oil prices, rare earth export prices, geopolitical risks, and China's mineral exports. Distance negatively affects supply dynamics in the wind model but not in the solar model. However, the originality of this study lies in its examination of China's role as a rare earth supplier for Europe's clean energy transition, integrated into a gravity model. Significantly, this research provides potential trade insights and formulates an economic policy implication framework to guarantee a steady supply of China's rare earths for Europe's green deal objectives, while addressing the associated geopolitical risks.

Synthesis, characterization and photophysical properties of three novel lanthanide materials

Three new lanthanide compounds with different structures, i.e. [Tb(2,6-naphthalenedisulfonic acid)(OH)(H2O)2]n (1), [Nd(HIA)2(NO3)(H2O)3]n2n(NO3)·nH2O (2; HIA = isonicotinic acid) and [Er6(H2O)12(NO3)6(OH)8(O)]2NO3·2H2O (3), were obtained from hydrothermal reactions. Their crystal structures were characterized with single-crystal X-ray diffraction. Compound 1 is characteristic of a two-dimensional (2-D) layer-like structure, compound 2 features a one-dimensional (1-D) chain-like structure, while compound 3 shows an isolated (0-D) Er6 hexanuclear structure. The solid-state UV/Vis diffuse reflectance spectra show that the semiconductor bandgaps are 2.89 eV, 3.12 eV and 4.64 eV for compounds 1, 2 and 3, respectively. The solid-state photoluminescent measurements exhibit that they can show green, red and blue emissions. These photoluminescence emissions are originated from the characteristic emissions of the 4f electron intrashell transitions of the 5D4 → 7F6 of the Tb3+ ions in compound 1, the 4F7/2 → 4S3/2 of the Nd3+ ions in compound 2 and the 4F9/2 (4F5/2) → 4I15/2 of the Er3+ ions in compound 3. Their CIE (Commission Internationale de I'Éclairage) chromaticity coordinates are (0.2451, 0.4041), (0.7334, 0.2666) and (0.1391, 0.0483). Their CCT (Correlated Color Temperature) are 8937 K, 400,100 K and 2654 K.

Photoelectric Interaction and Photochromic Mechanism of K0.5Na0.5NbO3 Ceramics.

Rare-earth materials are widely used in the optical field due to their rich energy-level structures, and if endowed with photoelectric response characteristics, they are expected to be applied to photoelectric multifunctional devices. In this paper, Ho3+- and Yb3+-codoped K0.5Na0.5NbO3 (KNN) ferroelectric ceramics are synthesized, and the up-conversion and down-conversion luminescence intensity as well as the decay degree after photochromism can be controlled by the content of Yb3+. Strong green luminescence visible to the naked eye is realized, and the maximum luminescence decay is more than 50%. 2 s of color change fully indicates that the ceramic has the characteristics of fast response photochromic, under the most efficient wavelength of 405 nm by changing the irradiation wavelength. By incorporating data from thermal and electrical stimulation experiments, a comprehensive photochromic mechanism diagram is constructed, where the photochromic properties are predominantly governed by defects. It is believed that this work will provide a theoretical basis for the design of high-performance photochromic ceramics.

Securing Rare Earth Permanent Magnet Needs for Sustainable Energy Initiatives.

Rare earth permanent magnets are vital in various sectors, including renewable energy conversion, where they are widely used in permanent magnet generators. However, the global supply and availability of these materials present significant risks, and their mining and processing have raised serious environmental concerns. This paper reviews the necessary legislative, economic, and technological measures that must be implemented to address these issues. While it may not be feasible to eliminate the risks associated with the availability of rare earth materials, researchers in the field of electrical generators can play a crucial role in significantly reducing the demand for newly mined and processed such materials, thereby mitigating the negative environmental impacts of their extraction and production.

Chemical Origins of Optically Addressable Spin States in Eu2(P2S6) and Eu2(P2Se6).

Lanthanide materials with a 4f7 electron configuration (8S7/2) offer an exciting system for realizing multiple addressable spin states for qubit design. While the 8S7/2 ground state of 4f7 free ions displays an isotropic character, breaking degeneracy of this ground state and excited states can be achieved through local symmetry of the lanthanide and the choice of ligands. This makes Eu2+ attractive as it mirrors Gd3+ in exhibiting the 8S7/2 ground state, capable of seven spin-allowed transitions. In this work, we identify Eu2(P2S6) and Eu2(P2Se6) as viable candidates for optically addressable spin states. The materials feature paramagnetic behavior at 2.0 ≤ T ≤ 400 K and μ0 H = 0.01 and 7 T. The field-dependent magnetization M(H) curve reveals a single-ion spin with effective magnetic moments comparable to the expected magnetic moment of Eu2+. Seven well-defined narrow peaks in the excitation and emission spectra of Eu2+ are resolved. Phonon contributions to the Eu2+ spin environment are evaluated through heat capacity measurements. Insights into how the spin-polarized band structure and density of states of the materials influence the physical properties are described by using density functional theory calculations. These results present a foundational study of Eu2(P2S6) and Eu2(P2Se6) as a feasible platform for harnessing the spin, charge, orbital, and lattice degrees of freedom of Eu2+ for qubit design.

Study on the optical properties of Sm3+ doped bismuth silicate crystals based on first principles

Abstract This study systematically investigated the effect of Sm3+ doping on the optical properties of bismuth silicate (Bi4Si3O12, abbreviated as BSO) crystals using first principles calculations based on density functional theory (DFT). By calculating the dielectric function, reflectivity, absorption coefficient, refractive index, conductivity, and energy loss function of BSO crystals under different Sm3+ doping ratios, we found that moderate Sm3+ doping can increase the dielectric function of BSO crystals, and the real part of the dielectric function represents the material’s ability to respond to the electric field, that is, the macroscopic polarization degree. Therefore, moderate Sm3+ doping enhances the polarization ability of BSO crystals. Simultaneously doping an appropriate amount can effectively enhance the conductivity and light (visible and infrared) absorption ability of BSO crystals, and reduce the energy loss between electrons in BSO crystals, thereby improving their luminescence performance. Specifically, when the Sm3+ doping ratio is 1/6, the optical properties of BSO crystals are significantly improved. These findings not only enhance the understanding of the mechanism of optical performance changes in rare earth ion doped BSO crystals, but also provide a theoretical basis for the development of new rare earth doped optical materials.