Multiple Rare Earth Research Articles

Czochralski growth and characterization of the multicomponent garnet (Lu1/4Yb1/4Y1/4Gd1/4)3Al5O12

This work demonstrates the potential for practical scalable growth of complex garnets and evaluates the implications of a multicomponent composition in the optical quality and elemental distribution of a Czochralski-grown crystal. Our experimental approach was designed to elucidate the relation between a complex garnet composition ${({\mathrm{Lu}}_{1/4}{\mathrm{Yb}}_{1/4}{\mathrm{Y}}_{1/4}{\mathrm{Gd}}_{1/4})}_{3}{\mathrm{Al}}_{5}{\mathrm{O}}_{12}$, crystal growth parameters, crystal structural, and elemental homogeneity. Our hypothesis is that combining multiple rare earths (REs) that will fractionally occupy the dodecahedral site in the aluminum garnet structure will result in a stable, single garnet compound that can be grown by the Czochralski method. Single-crystal and powder x-ray diffraction indicated a single garnet phase with an increasing unit cell volume from seed to tail. In addition, we propose that the pattern of elemental segregation will be based on the deviation of the ionic radius of each constituent RE from the average RE ionic radius of the multicomponent garnet. Electron probe microanalysis revealed that ions that are smaller than that average (${\mathrm{Lu}}^{3+}$ and ${\mathrm{Yb}}^{3+}$) are preferentially incorporated in the crystal, while elements that are larger than that average (${\mathrm{Gd}}^{3+}$) are rejected. The ionic radius of ${\mathrm{Y}}^{3+}$ is close to that average and yttrium segregation was minimal. The concentrations of the four REs are closer to stoichiometric on the tail end of the boule. Scanning electron microscopy and energy-dispersive x-ray spectroscopy analysis reveal Gd-rich inclusions with eutectic microstructures in the tail end of the boule.

Quadrivalent praseodymium in planetary materials

AbstractPraseodymium is capable of existing as Pr3+ and Pr4+. Although the former is dominant across almost all geological conditions, the observation of Pr4+ by XANES and Pr anomalies (both positive and negative) in multiple light rare earth element minerals from Nolans Bore, Australia, and Stetind, Norway, indicates that quadrivalent Pr can occur under oxidizing hydrothermal and supergene conditions. High-temperature REE partitioning experiments at oxygen fugacities up to more than 12 log units more oxidizing than the fayalite-magnetite-quartz buffer show negligible evidence for Pr4+ in zircon, indicating that Pr likely remains as Pr3+ under all magmatic conditions. Synthetic Pr4+-bearing zircons in the pigment industry form under unique conditions, which are not attained in natural systems. Quadrivalent Pr in solutions has an extremely short lifetime, but may be sufficient to cause anomalous Pr in solids. Because the same conditions that favor Pr4+ also stabilize Ce4+ to a greater extent, these two cations have similar ionic radii, and Ce is more than six times as abundant as Pr, it seems that Pr-dominant minerals must be exceptionally rare if they occur at all. We identify cold, alkaline, and oxidizing environments such as oxyhalide-rich regions at the Atacama Desert or on Mars as candidates for the existence of Pr-dominant minerals.

Identification of Multiple Rare Earths and Other Associated Elements in Zircon by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS), which is a powerful technique for the detection of minor and trace elements in a sample, has been used to analyze the enriched zircon mineral collected from the beach sands of southern Bangladesh. In addition to zirconium, a large number of rare earth elements viz. cerium, lanthanum, praseodymium, neodymium, ytterbium, gadolinium, dysprosium, erbium, samarium, europium, holmium and yttrium and other associated elements like hafnium, niobium, tantalum, magnesium, calcium, sodium, titanium and iron along with non-metals like phosphorus and silicon were detected in the enriched zircon samples by the LIBS technique. To the best of our knowledge, this is the first time that multiple rare earth elements have been identified in natural zircon by LIBS.
 Journal of Bangladesh Academy of Sciences, Vol. 44, No. 1, 59-68, 2020

Tailoring thermal properties of multi-component rare earth monosilicates

This work explores the possibility of tailoring the thermal conductivity and thermal expansion of rare earth monosilicates through the introduction of multiple rare earth cations in solid solution. Six rare earth monosilicates are studied: Sc2SiO5, Y2SiO5, Nd2SiO5, Dy2SiO5, Er2SiO5, and Yb2SiO5. Four equimolar binary cation mixtures and a five-cation equimolar mixture were characterized. Thermal expansion was measured up to 1200 °C with X-Ray Diffraction (XRD) and bulk thermal conductivity was measured by Hot Disk technique. The linear coefficient of thermal expansion (CTE) of mixed-cation systems followed a rule of mixtures, with average linear CTEs between 6 - 9 × 10−6 /°C. Scandium monosilicate showed a lower linear CTE value as well as a notably lower degree of CTE anisotropy than other rare earth monosilicates. Thermal conductivity was found to decrease below rule of mixtures values through increasing heterogeneity in rare earth cation mass and ionic radii, as expected for the thermal conductivity of solid-solutions. The five-cation equimolar RE2SiO5 (RE=Sc, Y, Dy, Er, and Yb) shows a thermal conductivity of 1.06 W/mK at room temperature, demonstrating that multi-component rare earth silicates are strong candidates for novel dual-purpose thermal and environmental barrier coatings.

Synthesis and phase stability of zirconia-lanthania-ytterbia-yttria nanoparticles; a promising advanced TBC material

ABSTRACT Advanced thermal barrier coatings (TBCs) developed by incorporating multicomponent rare earth oxide dopants into zirconia are promising alternative to replace yttria-stabilized zirconia (YSZ) thermal barrier coatings. In this study, a zirconia-based nanopowder coating doped by multiple rare earth oxides (YLaYbZr: 5.86 Mol.%Y2O3-1.99 Mol.%La2O3-1.98 Mol.%Yb2O3-ZrO2) was synthesized using co-precipitation technique which is advantageous in terms of simplicity and cost-effectiveness. The product was then characterized using X-ray diffraction (XRD) method and field emission scanning electron microscopy (FESEM). The stability of YLaYbZr compound was studied after a heat treating the product at 1300°C for 50 h. The results indicated that the initially obtained powder was a metastable tetragonal (t-prime) zirconia. Rietveld refinement of the XRD data from YLaYbZr powder after 50 h of heat treatment at 1300°C confirmed stabilization of zirconia in the t-prime phase with around 15 wt.% monoclinic impurity. Furthermore, FESEM results (before and after heat treatment) indicated orderly particles of uniform shape and size with a small tendency toward agglomeration.

Tailoring Thermal Properties of Ebcs in High Entropy Rare Earth Monosilicates

This work explores the possibility of tailoring the thermal conductivity and thermal expansion of rare earth monosilicates through the introduction of multiple rare earth cations in solid solution. Six rare earth monosilicates are studied: Sc2SiO5, Y2SiO5, Nd2SiO5, Dy2SiO5, Er2SiO5, and Yb2SiO5. Four equimolar binary cation mixtures and a high entropy five-cation equimolar mixture were characterized. Thermal expansion was measured up to 1200 ˚C with X-Ray Diffraction (XRD) and bulk thermal conductivity was measured by Hot Disk technique. The linear coefficient of thermal expansion (CTE) of mixed-cation systems followed a rule of mixtures, with average linear CTE between 6 - 9x10-6 /˚C. Scandium monosilicate showed a lower linear CTE value as well as a notably lower degree of CTE anisotropy than other rare earth monosilicates. Thermal conductivity was found to decrease below rule of mixtures values through increasing heterogeneity in rare earth cation mass and ionic radii, as expected for the thermal conductivity of solid-solutions. The high entropy mixture RE2SiO5 (RE=Sc, Y, Dy, Er, and Yb) shows a thermal conductivity of 1.06 W/mK at room temperature, demonstrating that high entropy rare earth silicates are strong candidates for novel dual-purpose thermal and environmental barrier coatings.

Development of REE-doped CaWO4single crystals as reference materials forin situmicroanalysis of scheeliteviaLA-ICP-MS

REE-doped CaWO4single crystals as reference materials forin situmicroanalysis of scheeliteviaLA-ICP-MS.

Core-shell mutual enhanced luminescence based on space isolation strategy for anti-counterfeiting applications

Introducing multiple rare earth ions into the same matrix can achieve multi-band emission, but would significantly worsen the otherwise excellent properties of other ions due to the annihilation mechanism. Therefore, the innovative idea of core/shell mutual enhanced luminescence is proposed based on the dual-mode luminescence of YVO4:Er3+,Yb3+@YPO4:Eu3+ oxide-based nanoparticles. This strategy of space isolation can not only effectively inhibit the energy transfer between the activators (Er3+→Eu3+), but also significantly enhances the luminescence of Er3+ in the core due to the reduction of surface defects via the protection of the shell. At the same time, the high intensity luminescence of Eu3+ in the shell is sensitized by VO43− in the core, which realizes the purpose of mutually reinforcing luminescence of the core and shell. Compared with physical mixing materials, core/shell nanoparticles achieve efficient and stable dual-mode imaging, our work introduces a promising material in anti-counterfeiting field.

Drug Delivery System with Multiple Rare Earth Ions Fluorescent-Labeling Drugs and Magnetic Nanoparticles.

The bifunctional drug delivery system combining magnetic nanoparticles and fluorophore possesses the characterization of magnetism and fluorescence. However, the accurate tracing of the drug release and diffusion pathway is affected by the separation of drug and fluorescent molecule. In this paper, we synthesized the fluorescent-labeling drug by covalently binding Aspirin with rare earth ions Terbium (Te) and Gadolinium (Gd), which was incorporated into chitosan microspheres with magnetic nanoparticles Fe₃O₄ to prepare magnetic and fluorescent drug delivery system. Investigated by Fourier transform infrared spectrometer, fluorescence spectrophotometer, X-ray diffraction, vibrating sample magnetometer, and scanning electron microscopy, the chitosan microspheres showed excellent fluorescent and magnetic properties. Compared with the single rare earth ion complex, the multiple rare earth ions complexes with Aspirin TbxGd1-x(Aspirin)₃ · 2H₂O (x 0.25, 0.5, 0.75) exhibited superior fluorescent intensity.

Effect of point defects on the thermal conductivity of Sc2O3-Y2O3 co-stabilized tetragonal ZrO2 ceramic materials

In this paper, the reduction mechanism in thermal conductivity of a series of Sc2O3-Y2O3 co-stabilized tetragonal ZrO2 ceramics is systematically discussed. The thermal conductivity is approximately 20–28% lower than that of 6–8 wt.% yttria-stabilized zirconia (YSZ). A phonon scattering model, on account of the influence of oxygen vacancy variation and cation mass fluctuation, is optimized and utilized to depict the thermal conductivity of these materials. For the samples with the same amount of oxygen vacancy, Sc3+ is more effective in lowering thermal conductivity than Y3+ due to the large mass difference with Zr4+, as evidenced by the scattering model and phonon vibrational density of states. The experimental and calculation results suggest that this optimized model is proved to be more effective in predicting the thermal conductivity of binary or multiple rare earth oxides co-doped tetragonal ZrO2 and guiding the compositional design of thermal barrier materials.

Selective Extraction of Rare Earth Elements Over TiO2 From Bauxite Residues After Removal of Their Fe-, Si-, and Al-Bearing Constituents

In our previous study, an intermediate material enriched with multiple rare earth elements (REEs, e.g., La2O3, Ce2O3, Sc2O3, and Y2O3) and TiO2 was obtained after removing iron, silica, and alumina from bauxite residues. For valorization of this valuable intermediate material, the selective leaching and separation of REEs and TiO2 by phosphoric acid leaching was investigated. Approximately 90% of REEs was leached from the material using 8- to 10-mol/L H3PO4 liquor at 150°C, while 98% of TiO2 was precipitated as Ti(HPO4)2·H2O in the leached residue, achieving selective extraction of REEs over TiO2. Scrubbing with dilute H3PO4 liquor during filtration could facilitate the formation of Ti(HPO4)2·H2O. The high extraction of REEs was a result of their distribution in the perovskite lattice, as demonstrated by the positive correlation between dissolutions of REEs and perovskite. A route for stepwise extraction of Fe, Si, Al, REEs, and Ti from bauxite residue was established.

Utilization of high entropy alloy characteristics in Er-Gd-Y-Al-Co high entropy bulk metallic glass

In the present study, we carefully evaluate the role of high entropy alloy (HEA) characteristics on glass-forming ability (GFA) and mechanical responses in a newly developed Er-Gd-Y-Al-Co high entropy bulk metallic glass (HE-BMG) by comparison with the Er-Al-Co and Er-Y-Al-Co bulk metallic glasses (BMGs). The addition of multiple rare-earth elements (REs) to Er-Al-Co BMG results in both higher fragility according to Adam-Gibbs theory and slower crystallization kinetics according to confusion principle. Based on these mutual competitions, the Er18Gd18Y20Al24Co20 HE-BMG can be successfully fabricated up to 5 mm in diameter for glass formation. In particular, the HE-BMG exhibits unexpected structural bias and more fragile manner via preferential covalent bonding of Co-Al and various RE-Al clusters, which leads to larger deviation from the typical BMGs' behavior in the relation between fragility and elastic properties. Furthermore, the HE-BMG effectively retards crystallization kinetics, which was confirmed by exceptionally sluggish nanocrystallization of multi-precipitates from metastable liquid and longer post-recalescence plateau duration in cooling curve of solidification from stable liquid. Indeed, the increased structural instability due to HEA characteristics (preferential short-range order and sluggish crystallization) in HE-BMGs reduces cut-off size of self-organized shear avalanches and increases the number of chaotic shear avalanches, which can distribute the applied strain more homogeneously, resulting in enhanced intrinsic ductility. Consequently, these results provide a guideline on how to design HE-BMGs with promising properties by utilizing HEA characteristics, and thus can give us a strategy for bridging BMG and HEA.

Estimating perfluorocarbon emission factors for industrial rare earth metal electrolysis

Rare earth (RE) metals have been widely applied in new materials, leading to their drastic production increase in the last three decades. In the production process featured by the molten-fluoride electrolysis technology, perfluorocarbon (PFC) emissions are significant and therefore deserve full accounting in greenhouse gas (GHG) emission inventories. Yet, in the ‘2006 IPCC Guidelines for National Greenhouse Gas Inventories’, no method currently exists to account for PFC emissions from rare earth metal production. This research aims to determine emission factors for industrial rare earth metals production through on-site monitoring and lab analysis of PFC concentrations in the exhaust gases from rare earth metal electrolysis. Continuous FTIR measurements and time-integrated samples (analysed off-site by high-precision Medusa GC–MS) were conducted over 24–60 h periods from three rare earth companies in China, covering production of multiple rare earth metals/alloys including Pr-Nd, La and Dy-Fe. The study confirmed that PFC emissions are generated during electrolysis, typically in the form of CF4 (∼90% wt of detected PFCs), C2F6 (∼10%) and C3F8 (<1%); trace levels of c-C4F8 and C4F10 were also detected. In general, PFC emission factors vary with rare earth metal produced and from one facility to another, ranging from 26.66 to 109.43 g/t-RE for CF4 emissions, 0.26 to 10.95 g/t-RE for C2F6, and 0.03 to 0.27 g/t-RE for C3F8. Converted to 211.60 to 847.41 kg CO2-e/t-RE for total PFCs, this emissions intensity for rare earths electrolysis is of lower (for most RE production) or similar (Dy-Fe production) level of magnitude to industrial aluminium electrolysis.

Quantifying Postfire Aeolian Sediment Transport Using Rare Earth Element Tracers

AbstractGrasslands, which provide fundamental ecosystem services in many arid and semiarid regions of the world, are undergoing rapid increases in fire activity and are highly susceptible to postfire‐accelerated soil erosion by wind. A quantitative assessment of physical processes that integrates fire‐wind erosion feedbacks is therefore needed relative to vegetation change, soil biogeochemical cycling, air quality, and landscape evolution. We investigated the applicability of a novel tracer technique—the use of multiple rare earth elements (REE)—to quantify soil transport by wind and to identify sources and sinks of wind‐blown sediments in both burned and unburned shrub‐grass transition zone in the Chihuahuan Desert, NM, USA. Results indicate that the horizontal mass flux of wind‐borne sediment increased approximately threefold following the fire. The REE tracer analysis of wind‐borne sediments shows that the source of the horizontal mass flux in the unburned site was derived from bare microsites (88.5%), while in the burned site it was primarily sourced from shrub (42.3%) and bare (39.1%) microsites. Vegetated microsites which were predominantly sinks of aeolian sediments in the unburned areas became sediment sources following the fire. The burned areas showed a spatial homogenization of sediment tracers, highlighting a potential negative feedback on landscape heterogeneity induced by shrub encroachment into grasslands. Though fires are known to increase aeolian sediment transport, accompanying changes in the sources and sinks of wind‐borne sediments may influence biogeochemical cycling and land degradation dynamics. Furthermore, our experiment demonstrated that REEs can be used as reliable tracers for field‐scale aeolian studies.

Exploring the limits of EDS microanalysis: rare earth element analyses

It is a great time to be a microanalyst. After a few decades of incremental progress in energy-dispersive X-ray spectrometry (EDS), the last decade has seen the accuracy and precision surge forward. Today, the question is not whether EDS is generally useful but to identify the types of problems for which wavelength-dispersive X-ray spectrometry remains the better choice. The full extent of EDS’s capabilities has surprised many. Low Z, low energy, and trace element detection have been demonstrated even in the presence of extreme peak interferences. In this paper, we will summarise the state-of-the-art and investigate a challenging problem domain, the analysis of minerals bearing multiple rare-earth elements.

Simulating producer responses to selected chinese rare earth policies

This study explores the effects of Chinese rare earth stockpiling, environmental taxation, and improvements in recovery rates on rare earth markets. It uses a Stackelberg model with a leading producer (legal Chinese producers) and two sequential followers (illegal Chinese producers and the Mount Weld mine in Australia), each producing multiple rare earths. The model is parameterized for the production and prices of separated rare earth oxides (REOs) from ore. Counterfactuals involving Chinese policies are compared to the no-policy, business-as-usual (BAU) scenario. The five counterfactuals are: (1) further Chinese State Reserve Bureau (SRB) stockpiling of neodymium, (2) further SRB stockpiling of dysprosium, (3) an environmental tax on the production of legal Chinese rare earths, (4) increased recovery rates of neodymium at legal Chinese operations, and (5) increased recovery rates of dysprosium also at legal Chinese operations. The BAU scenario and five counterfactuals are run with (a) four different levels of reference illegal Chinese production and (b) with and without the Chinese production quota, yielding 48 total outcomes (6×4×2). The first finding is that any SRB stockpile purchase increases the price of the stockpiled REO and increases legal Chinese ore production. However, given co-production, increased ore production involves more production of all REOs, and the prices of non-stockpiled REOs decrease. Thus if the stockpiled REO represents a large (small) portion of illegal Chinese and Mount Weld revenue, then illegal Chinese producers and the Mount Weld mine will increase (decrease) their production. An environmental tax decreases legal Chinese production, increases production by illegal Chinese producers and Mount Weld, and increases prices of all REOs. Increased legal Chinese recovery rates lead to increased legal Chinese production, decreased production by illegal Chinese producers and Mount Weld, and decreased REO prices. Increased levels of reference illegal Chinese production (a) exacerbate the policy-driven production increases or dampen production reductions of illegal producers and (b) conversely, for legal Chinese producers, reduce policy-driven production increases and further increase production reductions.

Structural and electromagnetic evaluations of YIG rare earth doped (Gd, Pr, Ho,Yb) nanoferrites for high frequency applications

Multiple rare earth metal cations (Gd, Yb, Ho and Pr) were doped in yttrium iron garnet (YIG) nanocrystalline ferrites. Following five samples i.e. YIG (Y3Fe5O12), Gd doped YIG (Y2.8Gd0.2Fe5O12), Pr doped YIG (Y2.8Pr0.2Fe5O12), Ho doped YIG (Y2.8Ho0.2Fe5O12) and Yb doped YIG (Y2.8Yb0.2Fe5O12) were prepared using sol-gel auto-combustion synthesis route. The samples were characterized via XRD, FTIR, SEM and VSM whereas VNA was also used to evaluate these samples for high frequency applications. XRD analysis confirms the peaks of garnet ferrites which show cubic phase structure for all YIG doped samples. The lattice constant in all the substituted garnet nanoferrites initially increased and then consequently decreased as the doping increased except for Pr-substituted YIG nanoferrites. This is due to the greater ionic radii of Pr as compared to other doped YIG nanoferrites. FTIR was used to find out the garnet phase in all the substituted YIG nanoferrites. The morphological features of the garnet nanoferrites were observed using the SEM images. High frequency measurements such as permittivity, permeability, dielectric losses, ac conductivity, electric modulus and Q factor of YIG and doped YIG nanoferrites were measured using VNA. Saturation magnetization, remanence, coercivity, squareness ratio, Bohr magneton and magneto crystalline anisotropy were measured from the magnetic hysteresis loops recorded by VSM. Pr-doped YIG show better dielectric and magnetic properties with lower losses at higher frequency suggest the use of these garnet nanoferrites for microwave high frequency devices and applications.

Effects of Ce/La misch metal content on microstructure evolution and mechanical properties of Mg-Zn-Y alloy

Although reinforced by quasicrystal I-phase, Mg-Zn-Y castings with low contents of Zn and Y exhibits still inadequate strength at elevated temperature. In this study, different contents of low-cost misch metal (Mm, the mixture of Ce and La) were added to ZW61 (Mg-6Zn-1.4Y) alloy to develop a new series of Mg alloys simultaneously containing multiple rare earth elements. The effects of Mm content on the microstructure, mechanical properties and fracture mechanisms both at room and elevated temperatures were systematically investigated. The results showed that the addition of Mm contributed to the grain refinement and the formation of T-phase. Besides, the precipitation behaviors of I-phase and W-phase were also changed due to the variation of Mm content. The yield and tensile strengths at room temperature firstly increased with 1wt% Mm addition, but then deteriorated slightly when adding more Mm. In contrast, the strengths at 200°C kept a continually increasing trend and the yield strength and ultimate tensile strength of ZW61-3Mm alloy were respectively increased by 20.9% and 28.0% compared with the corresponding strengths of ZW61 alloy, which were mainly attributed to the reduction in grain size and the high volume fraction of thermally-stable T-phase and W-phase.

Grain boundaries and electrical properties of Bi 0.85-x Pr 0.15 Dy x Fe 0.97 Mn 0.03 O 3 thin films

Abstract The chemical solution deposition route was employed to prepare Bi 0.85-x Pr 0.15 Dy x Fe 0.97 Mn 0.03 O 3 (BPDy x FMO, x = 0.00, 0.04–0.07) thin films. The structure and the electrical properties were investigated. With doped Dy 3+ ions, the coexisted two phases transform from the initial trigonal R 3 c : H structure and tetragonal P 4 structure into trigonal R 3 c : H and R-3 c : R structure. The grain sizes in BPDy x FMO thin films display a decreasing trend which indicates an increasing trend of the grain boundaries resistances. Meanwhile, an opposite trend between the grain boundaries resistance and the leakage current density appears because the resistance of grain boundaries blocks the leakage current. Due to multiple rare earth ions substitute for A-sites and single transition metal ions substitute for B-sites, the ferroelectricity of BPDy x FMO thin films deteriorates. At the same time, there will be aged ferroelectricties and broadened distributed switching fields. This is mainly attributed to the increasing grain boundaries and the formation of defects complexes which consist of positively charged defects and negatively charged defects. But more importantly, the Dy 3+ has a positive effect on the magnetism. The saturation magnetization of Bi 0.81 Dy 0.04 Pr 0.15 Fe 0.97 Mn 0.03 O 3 film is 2.39 emu/cm 3 .

Catalytic oxidation of dye waste water by biomass charcoal loaded multiple rare earth composite material

The main purpose of this study is to investigate the individual effect as well as the interactions of different influencing factors like catalyst dosage, aeration rate, temperature and pH on the removal of methylene blue (MB) using biomass charcoal loaded multiple rare earth composite material. Design-Expert 7.0 was used to design testing program and establish response surface model. The result showed that among the factors, catalyst dosage played the most important role, then pH value, aeration rate and temperature in turn. By the optimization of process parameters, the optimum experimental conditions were catalyst dosage of 2.50 g, aeration rate of 2.5 L·min-1, temperature of 21 °C and pH value of 12, under these optimum conditions, maximum predicted and observed decolorization rate were 100.00% and 99.61%, the observed value was well match with the predicted value.