Rare Earth Impurities Research Articles

(Y3+/Sm3+)-doped and co-doped CoFe2O4 for heterogeneous advanced oxidation process: structural, magneto-optical, and photocatalytic investigations.

The photocatalytic properties of CoFe2O4 nanoparticles were activated by the doping and co-doping of a low level of Y3+ and Sm3+ cations. After optimizing the annealing temperature, 900°C was found to be the optimal temperature for the successful incorporation of Y3+ and Sm3+ into the spinel structure. The purity of our samples annealed at 900°C was confirmed using several characterization methods, including PXRD, SEM, XPS, VSM, FTIR, and Raman spectroscopy. Thus, we were able to increase the photocatalytic degradation of orange G dye from 9.9 to 64.63% for the Sm3+-doped sample, 76.42% for the Y3+-doped sample, and even 85.81% for the co-doped sample under 60min of UV-visible light irradiation. The beneficial effect of samarium and yttrium doping and co-doping is attributed to several factors: the first factor is doped and co-doped rare earth impurities induce distortion in the lattice, the larger the ionic radii of dopant element, the highest is the photocatalytic activity; second factor, upon doping and co-doping of rare earth impurities in the structure of CoFe2O4 leads to the creation of donor state level within the band gap, causing the Fermi energy to shift near the conduction band. Third factor, co-doping produced strong interactions, which accelerated photocarrier mobility and transport; lastly, longer electron-holes lifetime. We have provided a detailed study of the structural, vibrational, and optical properties to support our conclusions.

First-principles investigation of near-field energy transfer between localized quantum emitters in solids

We present a predictive and general approach to investigate near-field energy transfer processes between localized defects in semiconductors, which couples first-principles electronic structure calculations and a nonrelativistic quantum electrodynamics description of photons in the weak-coupling regime. The approach is general and can be readily applied to investigate broad classes of defects in solids. We apply our approach to investigate an exemplar point defect in an oxide, the F center in MgO, and we show that the energy transfer from a magnetic source, e.g., a rare-earth impurity, to the vacancy can lead to spin nonconserving long-lived excitations that are dominant processes in the near field, at distances relevant to the design of photonic devices and ultrahigh dense memories. We also define a descriptor for coherent energy transfer to predict geometrical configurations of emitters to enable long-lived excitations, that are useful to design optical memories in semiconductor and insulators. Published by the American Physical Society 2024

Enhanced Spin-Orbit Torque Efficiency in Platinum-Gadolinium Oxide Nanocomposite Films.

Spin-orbit torque (SOT) has emerged as an effective means of manipulating magnetization. However, the current energy efficiency of SOT operation is inefficient due to low damping-like SOT efficiency per unit current bias. In this work, we dope conventional rare earth oxides, GdOy, into highly conductive platinum by magnetron sputtering to form a new group of spin Hall materials. A large damping-like spin-orbit torque (DL-SOT) efficiency of about 0.35 ± 0.013 is obtained in Pt0.70(GdOy)0.30 measured by the spin-torque ferromagnetic resonance (ST-FMR) technique, which is about five times that of pure Pt under the same conditions. The substantial enhancement of the spin Hall effect is revealed by theoretical analysis to be attributed to the strong side jump induced by the rare earth oxide GdOy impurities. Moreover, this large DL-SOT efficiency contributes to a low critical switching current density (8.0 × 106 A·cm-2 in the Pt0.70(GdOy)0.30 layer) in current-induced magnetization switching measurements. This systematic study on SOT switching properties suggests that Pt1-x(GdOy)x is an attractive spin current source with large DL-SOT efficiency for future SOT applications and provides another idea to regulate the spin Hall angle.

The temperature dependence investigation of the frequency dispersion of the electrical properties of lithium-iron spinel doped with La, Y

The temperature-frequency dependences of the electrical characteristics of Li2 Fe2,5-x Mex O4 (Ме=La;Y, x=0.01; 0.03; 0.05) spinels synthesized by the «sol-gel» autocombustion technology were obtained by the method of impedance spectroscopy in the temperature range of 298-473 K.
 Based on their analysis, the main mechanisms of conductivity of these materials in the studied temperature range were identified: hopping and activation, which are competing. The effect of doping lithium-iron spinels with rare-earth metal impurities on these conductivity mechanisms has been investigated. It has been established that the presence of impurities in small concentrations in the synthesized samples significantly decreases their conductivity, mainly due to destruction of the hopping mechanism of electronic conductivity.

Radiation shielding assessment for interventional radiology personnel: Geant4 dosimetry of lead-free compositions

The inherent biological hazards associated with ionizing radiation necessitate the implementation of effective shielding measures, particularly in medical applications. Interventional radiology, in particular, poses a unique challenge as it often exposes medical personnel to prolonged periods of high x-ray doses. Historically, lead and lead-based compounds have been the primary materials employed for shielding against photons. However, the drawbacks of lead, including its substantial weight causing personnel’s inflexibility and its toxicity, have raised concerns regarding its long-term impact on both human health and the environment. Barium tantalate has emerged as a promising alternative, due to its unique attenuation properties against low-energy x-rays, specifically targeting the weak absorption area of lead. In the present study, we employ the Geant4 Monte Carlo simulation tool to investigate various formulations of barium tantalate doped with rare earth elements. The aim is to identify the optimal composition for shielding x-rays in the context of interventional radiology. To achieve this, we employ a reference x-ray spectrum typical of interventional radiology procedures, with energies extending up to 90 keV, within a carefully designed simulation setup. Our primary performance indicator is the reduction in air kerma transmission. Furthermore, we assess the absorbed doses to critical organs at risk within a standard human body phantom protected by the shield. Our results demonstrate that specific concentrations of the examined rare earth impurities can enhance the shielding performance of barium tantalate. To mitigate x-ray exposure in interventional radiology, our analysis reveals that the most effective shielding performance is achieved when using barium tantalate compositions containing 15% Erbium or 10% Samarium by weight. These findings suggest the possibility of developing lead-free shielding solutions or apron for interventional radiology personnel, offering a remarkable reduction in weight (exceeding 30%) while maintaining shielding performance at levels comparable to traditional lead-based materials.

Impact of rare earth (La, Pr, Eu) impurities on the perovskite SrTiO3 for efficient photocatalytic activity

Owing to the growing demand for environmentally friendly technologies across a wide range of fields, including energy, environment and medicine, photocatalytic materials have gained a lot of interest in recent years. First-principles calculations were used in order to examine a variety of physical characteristics such as electronic density of states, structural, optical, and photocatalytic properties of pristine and rare-earth (RE = La, Pr, Eu) doped SrTiO3. The reported electronic band gap of pristine SrTiO3 is Eg = 3.03 eV, which is reasonably consistent with prior theoretical and experimental studies. On the other hand, related to Sr(1−x)RExTiO3, the obtained energy band gaps are 2.75 eV, 2.80 eV, and 2.90 eV associated with Eu-SrTiO3, Pr-SrTiO3, and La-SrTiO3 respectively. The narrowing of the electronic band gap of the studied systems is due to the incorporation of RE-doped SrTiO3, which greatly enhanced the visible light absorption spectra and photocatalytic properties. Thus, it can be concluded that adding RE elements to this kind of materials, is a suitable choice for optoelectronic and photocatalytic applications.

Inductively coupled plasma optical emission spectroscopic determination of trace rare earth elements in highly refractory gadolinium zirconate (Gd2Zr2O7).

Gadolinium zirconate (Gd2Zr2O7) belongs to the category of burnable absorber (BA) material in nuclear reactors. The high neutron-absorption cross sections of Gd isotopes (155Gd and 157Gd) implement negative reactivity in the reactor core to control the excess reactivity of the fuel at the beginning of the fission cycle. The presence of other rare earth elements, which can come from the starting material and/or may be taken up during the synthesis steps, will affect the negative reactivity calculation. Thus the chemical quality assurance of Gd2Zr2O7 concerning the other trace rare earth impurities is indispensable. Here in this work, we decided to quantify thirteen trace rare earth elements in Gd2Zr2O7 by inductively coupled plasma optical emission spectroscopy (ICP-OES). One of the matrix elements viz., zirconium was separated via precipitation using d,l-mandelic acid. The trace rare earths were determined in the presence of gadolinium matrix in solution. It was found that all thirteen rare earth elements can be quantified in the range of 0.25 to 2.5 mg L-1 in the presence of 516 mg L-1 of Gd with a relative standard deviation of 1-3%. This corresponds to the determination of a minimum of 0.25 mg analyte per g of Gd2Zr2O7. The method detection limits of all thirteen rare earth elements range between 0.01 and 0.075 mg g-1. The proposed methodology was validated by analyzing synthetic standards and real samples with spike addition.

Membrane distillation of a waste stream from neodymium‑iron‑boron scrap recovery: Performance and scaling mitigation

Neodymium‑iron‑boron (NdFeB) scraps contained 20–30 % rare earth elements such as neodymium, iron, boron, dysprosium, and praseodymium, which are valuable untapped rare earth resource. Hydrometallurgical extraction through hydrochloric acid treatment is often used to separate the rare earth metals and impurities in the NdFeB scraps, resulting in large amounts of acidic lixiviate and high-salinity brine, challenging to further treatment and detrimental to the environment if directly discarded. In this work, direct contact membrane distillation (DCMD) was explored to treat NdFeB scraps precipitation wastewater (NPW) by testing systematically three different hydrophobic commercial membranes. The impact of the membrane surface properties on the recovery performance and membrane scaling were investigated. The results showed that the membranes with strong hydrophobic properties and smaller pore size distributions possessed greater anti-scaling potential compared to the other materials. Additionally, the membranes with greater porosity offered longer stable operation at high flux, with the PTFE-0.22 membrane maintaining a flux over 20 kg/m2·h for up to 8 h. Membrane scaling caused by calcium carbonate during DCMD treatment was significantly mitigated by systematic chemical cleaning and after four cycles of testing, >75 % initial flux was restored via a simple acid cleaning. An average of 53.4 g/L sodium chloride with the purity of 99.3 % was obtained from the concentrated NPW by evaporation crystallization. This work demonstrated the potential of DCMD to act as a resource concentration and recovery tool on industrial effluents.

Negligible magnetic losses at low temperatures in liquid phase epitaxy grown Y3Fe5O12 films

Yttrium iron garnet (${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$; YIG) has a unique combination of low magnetic damping, high spin-wave conductivity, and insulating properties that make it a highly attractive material for a variety of applications in the fields of magnetics and spintronics. While the room-temperature magnetization dynamics of YIG have been extensively studied, there are limited reports correlating the low-temperature magnetization dynamics to the material structure or growth method. Here we investigate liquid phase epitaxy grown YIG films and their magnetization dynamics at temperatures down to 10 K. We show there is a negligible increase in the ferromagnetic resonance linewidth down to 10 K, which is unique when compared with YIG films grown by other deposition methods. From the broadband ferromagnetic resonance measurements, polarized neutron reflectivity, and scanning transmission electron microscopy, we conclude that these liquid phase epitaxy grown films have negligible rare-earth impurities present, specifically the suppression of Gd diffusion from the ${\mathrm{Gd}}_{3}{\mathrm{Ga}}_{5}{\mathrm{O}}_{12}$ (GGG) substrate into the ${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ film, and therefore negligible magnetic losses attributed to the slow-relaxation mechanism. Overall, liquid phase epitaxy YIG films have a YIG/GGG interface that is five times sharper and have ten times lower ferromagnetic resonance linewidths below 50 K than comparable YIG films by other deposition methods. Thus, liquid phase epitaxy grown YIG films are ideal for low-temperature experiments/applications that require low magnetic losses, such as quantum transduction and manipulation via magnon coupling.

ИССЛЕДОВАНИЕ СТРУКТУРНЫХ ОСОБЕННОСТЕЙ КРИСТАЛЛОВ LiNbO3:Y(0,24):Mg(0,63 мас. %), LiNbO3:Y(0,46 мас. %), LiNbO3:Mg(0,5 мас. %) ПО ИК-СПЕКТРАМ ПОГЛОЩЕНИЯ В ОБЛАСТИ ВАЛЕНТНЫХ КОЛЕБАНИЙ ОН-ГРУПП

Single crystals LiNbO3:Y(0.24):Mg:(0.63 wt. %), LiNbO3:Mg(0.5 wt. %), LiNbO3:Y(0.46 wt. %) were studied by infrared absorption spectroscopy in the area of valence vibrations of OH-groups. The absorption bands in the frequency range 3465–3488 cm–1 associated with the violation of stoichiometry in the crystal due to sharpened defects (VLi, NbLi) and formed complex defects VLi-ОН, NbLi-ОН. A part of Y3+ cations forms complex defects -ОН, -ОН- , which correspond to the absorption bands 3527, 3535 cm–1 in crystal LiNbO3:Y (0.46 wt. %). The introduction of magnesium alloying impurity into the double-doped crystal increases the effective distribution coefficient of the rare-earth impurity in the crystal and increases the luminescence of rare-earth ions by 8 times.

Structural and Spectroscopic Features of the Bixbyite-Type Yttrium Scandate Doped by Rare-Earth Ions

Yttrium scandate crystal fiber has been obtained through laser-heated pedestal growth. The crystal belongs to a bixbyite crystal structure and crystallizes in Ia3¯ space group. X-ray diffraction method shows a lattice parameter of a = 10.228(1) Å. Factor-group analysis of YScO3 Raman spectra points to high degree of disorder in crystal structure of the new compound. Spectral-kinetic investigation of the crystal fibers doped by rare-earth ions points to the presence of two independent active optical centers of rare-earth ions. Moreover, the character of rare-earth impurities’ distribution is independent on a rare-earth ionic radius size.

Comparison of the Preparation Process of Rare Earth Oxides from the Water Leaching Solution of Waste Nd-Fe-B Magnets’ Sulfate Roasting Products

The new process developed here consisting of sulfurization roasting transformation and water immersion can effectively realize the separation of rare earth elements (REEs) and impurities from spent Nd-Fe-B magnets. For the industrial application of the new process, it is critical to determine how to economically and efficiently prepare rare earth oxide (RExOy) products with higher purity from the obtained water leaching solution. Therefore, according to rare earth sulfate (RE2(SO4)3) solution characteristics, the oxalic acid precipitation–calcination method, sodium carbonate precipitation–calcination method, and double sulfates precipitation–alkali conversion–calcination method were optimized and compared. The results show that the recovery efficiency of REE recovery via the oxalic acid precipitation–calcination method is 99.44%, and the purity of RExOy is 99.83% under optimal technological conditions. However, the cost of oxalic acid precipitation is higher. The process consisting of the double sulfates precipitation–alkali conversion–calcination method is relatively complicated, the recovery efficiency of REEs is 97.95%, and the purity of the RExOy is 98.04%. The recovery efficiency of the REEs and the purity of the RExOy obtained from the sodium carbonate precipitation–calcination method are 99.12% and 98.33%, respectively. Moreover, the recycling cost of sodium carbonate precipitation is the lowest among the three processes for preparing RExOy, so it has industrial application potential. The obtained results for REE recovery from spent Nd-Fe-B magnets in this research can provide theoretical guidance for the innovation of the recycling process for REEs as secondary resources.

Analysis of corrosion fatigue steel strength of pump rods for oil wells

Purpose is to perform analysis of corrosion durability (fatigue) of pump rod materials in terms of various chemically active simulation environments, and study influence of economically modified rare-earth impurity on corrosion fatigue strength of pump rod materials. Methods. 40 and 20N2M steel grades have been applied as well as experimental steel (ES). Steel of the conditinal ES grade has been melted within a pilot site of Institute of Electric Welding Named after E.O. Paton of the National Academy of Sciences of Ukraine. The steel was alloyed economically by means of a micro impurity of a rare-earth element (REE) being 0.03% of cerium; in addition, it contained comparatively low concentration of sulfur and phosphorus as well as minor concentration of dissolved hydrogen. The following has been used as simulation environments: 1) NACE environment (i.e. 5% NaCl solution which contained 0.5% СН3СООН, and saturated H2S; t = 22 ± 2°C; pH = 3.8-4.0); 2) 3% NaCl solution without hydrogen sulphide. Once every day, the environment was replaced to oxygenate it up to 8-10 mg/l concentration. Findings. Stability against sulfide stress-corrosion cracking (SSCC), hydrogen initiated cracking (HIC), and corrosion fatigue of steel of deep pump rods for oil industry has been studied. It has been defined that the experimental steel, modified economically by means of micro impurities of a REE, meets NACE MR0175-96 standard in terms of chemical composition as well as strength; in turn, 20N2M and 40 steel grades have high resistance neither to SSCC (threshold stresses are < 0.8 s) nor to corrosion fatigue attack; moreover, steel grade 40 has demonstrated low resistance to HIC (CLR > 6% and CTR > 3%). Originality. It has been identified that corrosion fatigue attack results from hydrogen penetration of steel initiating its cracking and hence destruction under the effect of alternating loads accelerated by the action of corrosive environment. Further, surface micro destructions, influenced by micro stresses, transform into large discontinuities and cracks with following macro destructions. Practical implications. It has been proved that high resistance to corrosion cracking can be achieved by means of refining of pump-rod steel of ferrite and perlite type using metallurgical methods, i.e. 0.01-0.03% REE microalloying.

Origin assessment of uranium ores using multivariate statistical method based on their rare-earth elemental parameters

Origin assessment of nuclear materials is the key aim of nuclear forensics. Among the various fingerprints, rare-earth elements (REEs) are regarded as a powerful geological signature in authentication studies as they behave similarly during geologic and mining/milling processes. In this study, the combination of rare-earth impurities and Nd–Ce isotope ratios were proposed as a novel fingerprint for the origin assessment of uranium ores. A database was established, comprising mass spectrometric measurements of rare-earth elemental parameters of twenty-five samples from seven countries. The efficiencies of different multivariate statistical techniques, including cluster analysis (CA), principal component analysis (PCA) and linear discriminant analysis (LDA), were compared. The results showed that most of uranium ore samples were correctly classified according to geographical origins, and Nd–Ce isotope ratios played a key role in improving the classification. High recognition (100%) and satisfactory predictive ability (90%) of the developed LDA model proved that the proposed method is a powerful tool for tracing unknown uranium ore samples.

Review of separation and concentration techniques for impurities in rare earth-based materials for further spectral and mass spectral analysis

The effectiveness of using materials based on rare earth elements (REE) largely depends on their impurity composition, which affects their structure and properties. Before the analytical quality control of REE-based materials and initial substances for their production, it is necessary to determine both macrocomponents and impurity elements with high sensitivity and accuracy. A complex of atomic emission and mass spectral analytical methods is often used for the determination of impurities in REE-based materials in the range from 10–5 to 5.0 wt.%. However, the analysis of such materials, even using these modern high-sensitivity methods is a difficult task due to spectral and matrix interferences. Therefore, different preliminary separation/concentration procedures are needed to determine both rare earth and other impurities. This article reviews publications is devoted to preconcentration methods for spectral and mass spectral analysis of REEbased materials and, in part, a number of other analytical techniques. It was shown that the most common approaches are liquid extraction and chromatography. Sorption, cloud-point extraction and coprecipitation are also used. There is no universal method. Each of the methods discussed in this article has its own advantages and limitations. The analytical completion of the method confirms the effectiveness of the selected separation/concentration method in each specific case.

Advances in borate- and phosphate-based TL materials for in vivo dosimetry

Thermoluminescence (TL) materials are well known for a very large number of applications in various fields such as medical research, in vivo dosimetry, environmental dosimetry, personal dosimetry, etc. There are several TL materials available in the market such as fluoride, borate, phosphate, silicate, borosilicate glasses, etc. The TL properties of materials change with the doping of rare-earth and transition impurities in different hosts which are useful for different applications. These doped TL materials can be prepared by different techniques such as, the melt-quenching technique, combustion method, sol–gel method, and others. Radiations such as γ-rays, X-rays, β-rays, photon beam, electron beam, neutron beam, etc., can be used to irradiate these TL materials. In the present state of research, interest is being raised to develop new thermoluminescent materials for various applications in the field of material science and radiation therapy for in vivo dosimetry in view of the rise in the number of cancer patients across the globe. In the last few years, borate and phosphate-based TL dosimeters got more attention in radiation dosimetry. So, this review deals with the recent developments and advancements in borate- and phosphate-based TL materials for in vivo dosimetry.

Large phonon thermal Hall conductivity in the antiferromagnetic insulator Cu3TeO6

Phonons are known to generate a thermal Hall effect in certain insulators, including oxides with rare-earth impurities, quantum paraelectrics, multiferroic materials, and cuprate Mott insulators. In each case, a special feature of the material is presumed relevant for the underlying mechanism that confers chirality to phonons in a magnetic field. A fundamental question is whether a phonon Hall effect is an unusual occurrence-linked to special characteristics such as skew scattering off rare-earth impurities, structural domains, ferroelectricity, or ferromagnetism-or a much more common property of insulators than hitherto believed. To help answer this question, we have turned to a material with none of the previously encountered special features: the cubic antiferromagnet Cu3TeO6. We find that its thermal Hall conductivity [Formula: see text] is among the largest of any insulator so far. We show that this record-high [Formula: see text] signal is due to phonons, and it does not require the presence of magnetic order, as it persists above the ordering temperature. We conclude that the phonon Hall effect is likely to be a fairly common property of solids.

Tuning of quantum entanglement in a superconductor with transition-metal and rare-earth impurities: Effect of potential scattering on quantum phase transitions

Bipartite quantum entanglement of electron spins of a Cooper pair in a dirty $s$-wave superconductor is investigated at absolute zero temperature in terms of the exchange interaction and potential scattering as well as the relative distance between the two electrons. In the case of transition-metal impurities, we utilize the T-matrix approach to obtain the relevant Green's functions. We employ the two-electron spin-space density matrix, which is associated with the perturbed Green's functions. We show that a two-spin state can be described by the Werner state for dirty superconductors as well as for clean ones. We find that both the first and second quantum phase transitions (QPTs) are generated by the competition between potential scattering and other interactions. Meanwhile, it is not possible to determine the allowable value for each interaction individually. In the case of rare-earth impurities, concurrence, as a measure of bipartite entanglement, is discussed in terms of the relative distance and collision times for all finite and infinite Debye frequencies. The results confirm that quantum correlation and QPTs can be tuned by impurities.

Magnetoquantum oscillations in the specific heat of a topological Kondo insulator

Surprisingly, magnetoquantum oscillations (MQOs) characteristic of a metal with a Fermi surface have been observed in measurements of the topological Kondo insulator SmB6. As these MQO have only been observed in measurements of magnetic torque (dHvA) and not in measurements of magnetoresistance (SdH), a debate has arisen as to whether the MQO are an extrinsic effect arising from rare-earth impurities, defects, and/or aluminum inclusions or an intrinsic effect revealing the existence of charge-neutral excitations. We report here the first observation of MQO in the low-temperature specific heat of SmB6. The observed frequencies and their angular dependence for these flux-grown samples are consistent with previous results based on magnetic torque for SmB6 but the inferred effective masses are significantly larger than previously reported. Such oscillations can only be observed if the MQO are of bulk thermodynamic origin; the measured magnetic-field dependent oscillation amplitude and effective mass allow us to rule out suggestions of an extrinsic, aluminum inclusion-based origin for the MQO.

Optical spectroscopy and unusual temperature shift of f – f zero-phonon luminescence lines: KTaO3:Er

We present a study of KTaO3:Er (≈0.05%) single crystals based on a multifaceted approach including the use of optical absorption, far-infrared reflectivity, electron paramagnetic resonance, photoluminescence spectra, and ab initio simulations. We describe briefly the fundamental consequences of Er doping, in particular, stiffening of TO1 soft mode of KTaO3. We provide information about energy level structures controlling f – f optical transitions in Er3+, on formation of minor cubic octahedral and major orthorhombic Er3+ centers. It is revealed that the temperature shift of narrow zero-phonon emission lines is strikingly unusual being much larger than that typical for trivalent rare-earth impurities.