Rare Earth Substitution Research Articles

Effect of Rare Earth doping on Structural, Morphological, Optical, and Magnetic Properties of the Y1-x(Gd, Dy)xBaCuFeO5+δ (x = 0.2, 0.4, 0.6, and 0.8) Ceramics

The effect of the rare earth (RE) ion substitution on the structural, morphological, optical and magnetic properties of the Y1-xRExBaCuFeO5 (RE = Gd, Dy; x = 0.2, 0.4, 0.6, and 0.8) multiferroic compounds grown by the solid-state reaction is evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), dispersive X-ray spectroscopy (EDX), reflectance spectroscopy techniques diffuse (UV-vis-NIR) and vibrating sample magnetometry (VSM). The results indicate that the RE substitution led to growth of single-phase materials, with a tetragonal structure and P4mm symmetry. The morphological analysis shows the formation of polycrystalline materials composed of grains of various shapes and sizes. Furthermore, the compositional analysis reveals that the materials do not present elements other than those used in the synthesis. The band gap (Eg) is tuned from 0.88 to 0.90 eV upon RE substitution. The magnetization curves obtained in the Zero-Field-Cooled/Field-Cooled (ZFC-FC) modes between 50 and 390 K, reveal a paramagnetic behavior, which could be attributed to the dominance exerted by the magnetic moments of the Gd/Dy ions.

Importing Atomic Rare-Earth Sites to Activate Lattice Oxygen of Spinel Oxides for Electrocatalytic Oxygen Evolution.

Spinel oxides have emerged as highly active catalysts for the oxygen evolution reaction (OER). However, due to covalency competition, the OER process on spinel oxides often follows an arduous adsorbate evolution mechanism (AEM) pathway. Herein, we propose a novel rare-earth sites substitution strategy to tune the lattice oxygen redox of spinel oxides and bypass the AEM scaling relationship limitation. Taking NiCo2O4 as a model, the incorporation of Ce into the octahedral site induces the formation of Ce-O-M (M: Ni, Co) bridge, which triggers charge redistribution in NiCo2O4. The developed Ce-NiCo2O4 exhibits remarkable OER activity with a low overpotential, satisfactory electrochemical stability, and good practicability in anion-exchange membrane water electrolyzer. Theoretical analyses reveal that OER on Ce-NiCo2O4 surface follows a more favorable lattice oxygen mechanism (LOM) pathway and non-concerted proton-electron transfers compared to pure NiCo2O4, as further verified by pH-dependent behavior and in situ Raman analysis.18O-labeled electrochemical mass spectrometry directly demonstrates that oxygen originates from the lattice oxygen of Ce-NiCo2O4 during OER. It is discovered that electron delocalization of Ce 4f states triggers charge redistribution in NiCo2O4 through the Ce-O-M bridge, favoring antibonding state occupation of Ni-O bonding in [Ce-O-Ni] site, thereby activating lattice oxygen redox of NiCo2O4 in OER.

Power capacity enhancement and loss reduction induced by limited solid solubility of Ho 3+ rare-earth substitution in NiCuZn spinel ferrites

Power capacity enhancement and loss reduction induced by limited solid solubility of Ho ³⁺ rare-earth substitution in NiCuZn spinel ferrites

Broadband spectral cyan emission phosphor for full-spectrum LED caused by interstitial site occupation

The phosphor with a highly condensed, rigid framework structure and a single crystallographic site often exhibit symmetrical narrow-band emission. It is challenging to achieve broadband emission by doping Eu2+ ions in similar structures. Here, we propose to control the occupation and quenching concentration of Eu2+ ions in a single-site matrix Sc2Si2O7 to increase efficiency and precise regulation of luminescence spectra substantially. The analysis of photoluminescence spectroscopy through steady-state, transient-state, and Gaussian fitting techniques has discovered two emission centers despite the presence of a single rare-earth substitution site. The theoretical calculations and bond valence sum subsequently prove that Eu2+ ions prefer substituting the Sc3+ and interval sites to emit intense cyan light. Under 340 nm excitation, broad cyan-emission (FWHM = 115 nm) is exhibited with a high quantum yield of 60.67 %. The present phosphor exhibits pronounced thermal stability, and the emission intensity can still keep 68.3 % at 170 °C compared to that at atmospheric temperature. The Sc2Si2O7: Eu2+ phosphor boasts exceptional potential as a highly efficient cyan component in full-spectrum WLEDs. By replacing the blue light component commonly found in WLEDs, the intelligent and healthy alternative Sc2Si2O7: Eu2+ phosphor can effectively decrease the harmful blue light. This work also highlights the critical need to analyze local phosphor distortions upon rare-earth substitution, especially in single crystallographic site structures.

Effect of rare earth substitution on magnetic properties of strontium hexaferrite prepared by Pechini method

This study presents a comprehensive investigation into the impact of substituting rare earth elements on the magnetic properties of strontium hexaferrite. The samples, synthesized by the sol-gel Pechini method, followed the formula Sr1-xRexFe12O19 with Re = Gd, Sm, Nd, Pr, and La, for 0.025 ≤ x ≤ 0.100. The findings revealed that Re substitution promotes a considerable increment of the coercive field. However, the magnetic yield dropped with increasing the Re content. Therefore, the higher coercivity field, largest magnetization and maximum energy product (BHmax) were reached for samples with x = 0.025. This tendency was consistent across all rare earth-substituted samples although the hexaferrite substituted with samarium and praseodymium showed the strongest hard-magnetic properties. This behavior has been attributed to a reduction of the interaction field due to the emergence of a monodomain structure, and to the limited solubility of rare earth elements within the structure of strontium hexaferrite.

Effect of Rare-Earth Element Substitution in Superconducting R3Ni2O7 under Pressure

Abstract Recently, high temperature (T c ≈ 80 K) superconductivity (SC) has been discovered in La3Ni2O7 (LNO) under pressure. This raises the question of whether the superconducting transition temperature T c could be further enhanced under suitable conditions. One possible route for achieving higher T c is element substitution. Similar SC could appear in the Fmmm phase of rare-earth (RE) R3Ni2O7 (RNO, R = RE element) material series under suitable pressure. The electronic properties in the RNO materials are dominated by the Ni 3d orbitals in the bilayer NiO2 plane. In the strong coupling limit, the SC could be fully characterized by a bilayer single 3d x 2–y 2 -orbital t–J ∥–J ⊥ model. With RE element substitution from La to other RE element, the lattice constant of the Fmmm RNO material decreases, and the resultant electronic hopping integral increases, leading to stronger superexchanges between the 3d x 2–y 2 orbitals. Based on the slave-boson mean-field theory, we explore the pairing nature and the evolution of T c in RNO materials under pressure. Consequently, it is found that the element substitution does not alter the pairing nature, i.e., the inter-layer s-wave pairing is always favored in the superconducting RNO under pressure. However, the T c increases from La to Sm, and a nearly doubled T c could be realized in SmNO under pressure. This work provides evidence for possible higher T c R3Ni2O7 materials, which may be realized in further experiments.

Research Progress on Controllable Absorption Properties of Rare Earth Element Doped Electromagnetic Wave Absorbing Materials†

Comprehensive SummaryThe utilization of rare earth (RE) elements is pivotal in wave absorption. In particular cases, RE group elements manifesting unique 4f electron layer structures are doped as impurities into certain materials, which is a practical and reliable method for regulating these materials' magnetic and electrical properties. Moreover, ferrites and metal‐organic frameworks (MOFs), standing out among conventional and emerging wave‐absorbing materials, can achieve significantly enhanced wave absorption through RE doping or substitution. Numerous scholars have dedicated massive research over a substantially long time to explore the utilization of RE elements to reinforce the absorption of these two materials. Therefore, consolidating and summarizing such efforts are crucial and necessary. This review aims to clarify the underlined mechanism of electromagnetic wave (EMW) absorption and elaborate on the impact of RE doping by providing a comprehensive overview of recent progress in ferrites and MOFs dopped with RE elements. Finally, the limitations associated with RE doping in such materials are delineated, and the upcoming prospects for its application are highlighted. Key ScientistsIn 1947, J. A. Marinky et al. obtained promethium from uranium fission products. From the isolates of yttrium soil in 1794 to the discovery of promethium in 1947, it took more than 150 years. In 1975, Guangxian Xu found that the rare earth solvent extraction system has the basic "constant mixed extraction ratio" rule. In 1984, the theory of "one‐cavity multi‐mode" was proposed by Weigan Lin to improve the electromagnetic wave theory further and develop the theory of absorbing materials. In 1995, Omar M. Yaghi synthesized the first MOFs in history, and since then, they have been widely used in gas adsorption and separation and other fields because of their large specific surface area and adjustable pore structure. In recent years, various functional materials based on MOFS‐derived carbon have been studied endlessly. Masato Sagawa, known for inventing NdFeB magnets, won the "28th Japan Prize" in 2012. In recent years, Renchao Che has promoted the development of interface theory and magnetic theory in the field of wave absorption. In addition, Jiurong Liu is committed to developing various wave‐absorbing materials and the respective theoretical research and continues to promote the development of wave‐absorbing materials to "thin, light, wide and strong".

Comprehensive improvement of AB2 hydrogen storage alloy: Substitution of rare earth elements for different A-side alloys

Rare earth substitution enhances the activation, absorption/desorption properties of hydrogen storage alloys, a crucial research area. Despite the extensive variety of A-site elements in multicomponent alloys, there remains a scarcity of reports on how to enhance the hydrogen storage capacity of alloys by substituting different elements with rare earth elements at the A-site, which needs to be further explored. In this study, the AB2 type Ti-Mn based hydrogen storage alloy was selected as the research object, and the effect of replacing different elements in the A-position by rare earth elements with equal atomic ratios was systematically analyzed by replacing the hydrogen absorption elements Ti/Zr with the rare earth metal Ce. The result reveals that Ce substitution significantly enhances the hydrogen storage and cyclic performance of the alloys, with Ce substituting for Ti showing superior performance. Theoretical calculations indicate that Ce substitution for Ti in alloys leads to lower formation energy and easier hydrogen absorption than Ce substitution for Zr. Beyond the influence of the Lundin’s theory, this work proposes for the first time that the difference in electronegativity between substituent elements may one of the crucial factors affecting the hydrogen storage performance of alloys. The greater difference in electronegativity may lead to a higher hydrogen storage capacity of the hydrogen storage alloy. This opens a new avenue for research into doping/substitution modifications of hydrogen storage alloy elements. These findings not only enrich the knowledge on element doping modification but offer valuable insights for future research on rare earth-doped modification of hydrogen storage alloys.

2:17-type SmCo permanent magnets with controllable remanence temperature coefficients via substitution of heavy rare earth elements

2:17-type SmCo permanent magnets with controllable remanence temperature coefficients via substitution of heavy rare earth elements

Enhanced energy storage performance, breakdown strength, and thermal stability in compositionally designed relaxor Eu3+ substituted Na0.2K0.3Bi0.5TiO3

Lead-free Eu3+ substituted NKBT ceramics (Na0.2K0.3Bi0.5-xEuxTiO3, x = 0 (Eu 0),0.02(Eu 2),0.04(Eu 4), and 0.06(Eu 6)) were strategically designed via a local random field approach. The structural evolution had been confirmed through X-ray diffraction analysis. The observation of a broad dielectric curve supported the enhanced relaxor nature and the phenomena reflected in the P-E and S-E loops. The diffuse phase transition transforms to the plateau-type feature with excellent thermal stability with ±20 % and ± 40 % variation in dielectric constant over the temperature range of 120 to 500 °C and 90 to 500 °C, respectively in Eu 4. A large recoverable energy density of 1.7 J/cm3 with a high breakdown strength of 188 kV/cm was achieved in the Eu 2 sample at room temperature, making it a potential candidate for energy storage application. Moreover, the frequency stability (0.1 to 500 Hz range), thermal stability (45 °C to 85 °C), and fatigue measurement (10−1 to 106 cycles) were performed from the application point of view. The highest efficiency (82 %) was also achieved in the Eu 6. The negligible Sneg of Eu-rich compositions proves the existence of a relaxor state when the field is removed, and it transforms into the ergodic relaxor state. Furthermore, the SRBRF model is exploited to understand and correlate the transformation from normal to relaxor ferroelectrics with their properties. The current study provides a novel idea for compositional design for energy density, efficiency, and thermal stability ceramics by modifying and creating weakly coupled polar phases with rare earth substitution.

Study on Water Splitting of the 214-Type Perovskite Oxides LnSrCoO4 (Ln = La, Pr, Sm, Eu, and Ga).

We present a study on the electrocatalysis of 214-type perovskite oxides LnSrCoO4 (Ln = La, Pr, Sm, Eu, and Ga) with semiconducting-like behavior synthesized using the sol-gel method. Among these five catalysts, PrSrCoO4 exhibits the optimal electrochemical performance in both the oxygen evolution reaction and the hydrogen evolution reaction, mainly due to its larger electrical conductivity, mass activity, and turnover frequency. Importantly, the weak dependency of LSV curves in a KOH solution with different pH values, revealing the adsorbate evolving mechanism in PrSrCoO4, and the density functional theory (DFT) calculations indicate that PrSrCoO4 has a smaller Gibbs free energy and a higher density of states near the Fermi level, which accelerates the electrochemical water splitting. The mutual substitution of different rare-earth elements will change the unit-cell parameters, regulate the electronic states of catalytic active site Co ions, and further affect their catalytic performance. Furthermore, the magnetic results indicate strong spin-orbit coupling in the electroactive sites of Co ions in SmSrCoO4 and EuSrCoO4, whereas the magnetic moments of Co ions in the other three catalysts mainly arise from the spin itself. Our experimental results expand the electrochemical applications of 214-type perovskite oxides and provide a good platform for a deeper understanding of their catalytic mechanisms.

Effect of rare earth (Sm3+) substitution in mixed Ni-Zn-Co ferrites: Structural, magnetic, and DC electrical resistivity studies

NiZnCo ferrite has good magnetic properties and is one of the core materials used in magnetic devices. The solid-state reaction approach is utilized to synthesize Ni0.4Zn0.35Co0.25Fe2-xSmxO4 (x = 0.0, 0.02, 0.04, 0.06, 0.08, and 0.1) ferrites for investigation of structural, morphological, functional, magnetic and electrical resistivity properties using various characterization techniques. The techniques used for characterization were XRD, SEM, FTIR, VSM, and DC electrical resistivity. XRD spectra were used to determine phase confirmation, cubic crystallite size, andtheir variation with dopant content. No additional phase or impurity was found. The SEM pictures revealed ahomogeneous spherical particle formation with minimal porosity. With absorption bands under 1000 cm−1, FTIR spectra indicate the formation of a spinel structure. Tetrahedral (580 to 599 cm−1) and octahedral (388 to 399 cm−1) bond changes can be seen in infrared spectra. The magnetic hysteresis curves revealed soft ferromagnetic behavior, with coercivity (Oe) (532.13 to 312.10Oe) rising and saturation magnetization (Ms) (83.51 to 60.75 emu/g) falling as doping concentration increased. The DC electrical resistivity of synthesized nanoparticles with various compositions was measured against higher temperatures to confirm their semiconductor nature. The findings demonstrated the typical decreasing trend with rising temperature.

Experimental and theoretical studies on a Mg2InRE-type prismatic precipitate plate in a series of Mg-In-RE ternary alloys

In precipitation-hardening Mg-In-Sm alloy, a category of novel Mg2InSm prismatic plates have been built successfully and its crystal structure and atomic coordination were studied by atomic scale high-angle annular dark-field scanning transmission electron microscopy. The Mg2InSm plate has an orthorhombic structure, whose stability can be verified by first-principles calculations. Similarly, with the substitution of other rare earth (RE) for Sm, a series of Mg2InRE orthorhombic structures are also predicted to be stable. The findings are expected to guide the future design of effective precipitation strengthening phases in Mg–based alloys.

Mesoporous RE0.5Ce0.5O2-x Fluorite Electrocatalysts for the Oxygen Evolution Reaction.

Developing highly active and stable electrocatalysts for the oxygen evolution reaction (OER) is key to improving the efficiency and practical application of various sustainable energy technologies including water electrolysis, CO2 reduction, and metal air batteries. Here, we use evaporation-induced self-assembly (EISA) to synthesize highly porous fluorite nanocatalysts with a high surface area. In this study, we demonstrate that a 50% rare-earth cation substitution for Ce in the CeO2 fluorite lattice improves the OER activity and stability by introducing oxygen vacancies into the host lattice, which results in a decrease in the adsorption energy of the OH* intermediate in the OER. Among the binary fluorite compositions investigated, Nd2Ce2O7 is shown to display the lowest OER overpotential of 243 mV, achieved at a current density of 10 mA cm-2, and excellent cycling stability in an alkaline medium. Importantly, we demonstrate that rare-earth oxide OER electrocatalysts with high activity and stability can be achieved using the EISA synthesis route without the incorporation of transition and noble metals.

Improved energy storage performance and thermal stability of hafnium-substituted strontium sodium niobate tungsten bronze ceramics.

Dielectric capacitors are widely used in the field of pulsed power systems owing to their ultra-fast charge and discharge capacity; however, considering the complex environment they face in practical applications, how to further improve their thermal stability is an urgent issue that needs to be solved. Tungsten bronzes have the potential to broaden the temperature stability range owing to their unique structure, but only few studies have focused on them. Herein, lead-free Sr4-x La x Na2Hf x Nb10-x O30 ceramics with a tungsten bronze structure were synthesized, and their energy storage properties were comprehensively characterized. With proper Hf substitution in the B site and rare earth substitution in the A site, significantly enhanced relaxor behavior is induced, leading to a broad plateau of the dielectric curve, slim polarization-electric field loop, high energy storage efficiency and stable capacitive performance over a wide temperature range. In addition, an improved microstructure with fewer defects, decreased average grain size, increased band gap and resistance were obtained, which benefit to the increase in breakdown strength and energy storage density. Finally, improved energy storage performance and thermal stability were achieved for the compounds, with W total = 3.6 J cm-3, W rec = 2.9 J cm-3, η = 80% and stable temperature range = 20-160 °C. Thus, the current system is a promising candidate for application in temperature-stable dielectric capacitors.

Crucial role of Mg on phase transformation and stability of Sm–Mg–Ni-based AB2 type hydrogen storage alloy

Rare earth–Mg–Ni-based alloys are promising candidate for high-capacity hydrogen storage materials, and Mg is the key elements to maintain its crystal structure stable. In order to understand the role of Mg element in rare earth–Mg–Ni based alloys, the alloys with the composition of RE1–xMgxNi1.97Co0.03Al0.07 (RE = Sm0.80Y0.20; x = 0.35, 0.44, 0.52) were synthesized by powder sintering treatment. The increasing Mg content promotes the phase transformation from SmNi2 (Fd-3 m group) phase to MgCu4Sn-type (F-43 m group) phase. First-principle calculations and XRD simulations show that Mg element is reasonably approximated as the para-position substitution of rare earth elements at 4c sites when it enters into the unit cell of SmNi2 phase. The Sm0.38Y0.10Mg0.52Ni1.93Co0.03Al0.05 alloy with Mg fully occupying the 4c sites forms a stable structure, and it shows flat hydrogen absorption/desorption platforms, with a hydrogen absorption capacity of 1.12 wt%. Meanwhile, it has more excellent cycling stability. After 20 cycles of hydrogen absorption, the crystal structure of the alloy still maintains MgCu4Sn-type phase, and the capacity retention rate can reach 94.42 %.

Effect of rare earth substitution on electromagnetic and microwave absorption properties of nickel-cobalt nano ferrite

Oxygen vacancy engineering is one of the most effective strategies for tuning the microstructural properties of oxide nanomaterials. However, the connection between oxygen vacancies and electromagnetic (EM) wave absorption capacities is unclear. Herein, oxygen vacancy-boosted microwave absorption is realized over Gd-doped Ni0.5Co0.5Fe2O4 (NCFO) nanoceramics. All magnetic properties are studied with the influence of induced lattice strain. Except for Ni0.5Co0.5 Gd0.075Fe1.925O4 (NCFOG3), which has an elevated saturation magnetization (Ms) of 63 emu/g, the Ms decreases with increasing Gd content. In addition, remnant magnetization (Mr), coercivity (Hc), and anisotropic constant (K) increased until Ni0.5Co0.5 Gd0.050Fe1.95O4 (NCFOG2) and then declined. The EM wave parameters: dielectric permittivity (ϵ'), magnetic permeability (μ'), dielectric loss (ϵ''), and magnetic loss (μ'') are systematically examined and found in the ranges of 2.07–3.5, 1.73–4.7, (4 × 10-2) – (2.2 × 10-1) and 0.18–0.35 respectively. Our finding shows that a small amount of Gd favors the high oxygen vacancy concentration, an appropriate lattice defect, and high magnetic and dielectric losses. The possible mechanism for EM wave absorption revealed the largely localized electrons and dipole centers created by the numerous oxygen vacancies causing the multiple reflection and scattering, which enhanced conductive loss, defect, and dipole polarizations. The maximum reflection loss (RL) -28.37 dB is observed at 17.80 GHz of a 2 mm thick sample for NCFOG3. This research reveals a distinct link between oxygen vacancy defects and EM wave dissipation capability, providing important information for developing better EM wave absorbents.

Effect of rare earth substitution on pyroelectric, ferroelectric, and piezoelectric properties lead-free Ba0.85Ca0.12RE0.03Ti0.90Zr0.04Nb0.042O3 (RE = Ce or Pr) ceramics

Effect of rare earth substitution on pyroelectric, ferroelectric, and piezoelectric properties lead-free Ba0.85Ca0.12RE0.03Ti0.90Zr0.04Nb0.042O3 (RE = Ce or Pr) ceramics

Study of magnetization of ferrite with Rare Earth and Ca substitutions

Study of magnetization of ferrite with Rare Earth and Ca substitutions

Impact of erbium substitution on structural, dielectric, spectral, and microwave absorption properties of Ba3Co2Fe24O41 Z-type hexa-ferrites for microwave devices applications

A series of erbium-substituted Z-type hexaferrites with composition Ba3Co2ErxFe24-xO41 (0.00≤ x ≤ 0.12, Δx = 0.03) was synthesized via the sol-gel auto combustion technique and sintered at 1200 °C for 5:30 h. XRD analysis confirmed the single phase crystals throughout the samples. Incorporating erbium ions into a Z-type hexagonal lattice showed improved structural parameters. The lattice parameters (a, c) exhibited an increasing trend with the rare earth (Erbium) substitution in the range of 5.884–5.891 nm and 52.561–52.770 nm. Scherrer's equation was used to find crystallite size in 28–30 nm range. Absorption bands of ferrite phase were confirmed by Fourier Transform Infrared Spectroscopy. Dielectric characteristics of synthesized materials were studied through Epsilometer R60 VNA over a frequency 1 MHz to 6 GHz range. Variations in dielectric parameters were observed by substituting erbium ion into a Z-type hexaferrite lattice. The magnitude of the dielectric constant, AC conductivity, tangent loss, and dielectric loss increases at higher frequencies. While, dielectric constant, AC conductivity, loss factor, and tangent loss decrease with Erbium substitution. The high value of Q-factor ∼10232 at 0.87 GHz was observed. The cole-cole plots in impedance analysis confirmed the character of grains and grain boundaries in the conduction mechanism. Minimum reflection loss (RL) was −67 dB for the sample x = 0.06 at 0.2 GHz. At 1.28 GHz frequency, RL = −46 dB was observed for sample x = 0.03. The morphological study (SEM) revealed the hexagonal platelet-type grains with an average grain size of 2.48–2.73 μm. Minimum reflection loss, small crystallite size <50 nm, and high-quality factor suggested that these materials are suitable candidates for microwave absorbers, resonant circuits, multi-layer chip inductors, and high-frequency devices.