Rare Earth Er Research Articles

The Effect of Solvents and Rare-Earth Element (Er, Yb) Doping on Suspension Stability of Sol-Gel Titania Nanoparticles.

The effects of solvent on the suspension stability of titanium dioxide (TiO2) nanoparticle (NP)-doped rare-earth elements (Er and Yb) were evaluated. Pure and doped TiO2 NPs were successfully prepared by the sol-gel method under the supercritical drying conditions of ethanol. Doped nanopowders were prepared with 5 mol% Er or 5 mol% Yb concentration, and co-doped nanopowders were prepared with fixed 5 mol% Er concentration and various Yb concentrations of 5 and 10 mol%. TiO2 NP suspensions with diverse solvents, such as water, ethanol, methanol, and butanol, were prepared. The nanopowders were characterized by studying their structural and morphology properties. The NP size analysis revealed the average size of TiO2 as approximately around 7-12 nm. Suspensions of TiO2 NPs in different solvents were prepared by a two-step powder dispersion process using several ultrasonication methods. The aim of this paper was to prepare a stable suspension for a certain time period and then to produce doped and undoped TiO2 NP coatings for photovoltaic application. The effects of concentration, dopants, and solvents on the dispersibility and stability of TiO2 suspensions were evaluated. The UV-visible spectroscopy, zeta potential measurements, particle size distribution, SEM, and Hamaker 2 software confirm that the 5%Er-10%:TiO2 suspension exhibits a good stability and stable suspension improved by co-doped rare.

Effects of rare-earth doping on the ionic conduction of CeO2 in solid oxide fuel cells

Rare-earth-doped CeO2 have been found to enhance the ionic conductivity of ceria-based electrolytes in solid oxide fuel cells (SOFCs) because trivalent rare-earth cations can spontaneously induce oxygen vacancies. Experimentally, it has been shown that the rare-earth elements La, Nd, Sm, Gd, Tb, Dy, and Er are likely candidates for electrolyte doping. However, the performances differ for the trivalent cations, suggesting that rare-earth doping plays multiple roles instead of only increasing the oxygen vacancies. First-principles calculations are performed on a series of rare-earth-doped CeO2 systems to study the doping effects on the ionic conductivity. It is found that the migration barriers of the oxygen ions are significantly different for the different dopants and depend on the dopant's radius. Gd-, Dy-, Er-, and Tb-doping results in small migration barriers and enhances the ionic conductivity. We also calculate the formation energies (Evac) of the intrinsic oxygen vacancies due to thermal excitation. It is found that the Sm- and Gd-doped ceria systems have the smallest Evac values. The electronic structures indicate that the band gaps are not sensitive to the dopant elements but are very sensitive to the fluctuations in the oxygen content.

Microstructural and electrical characterizations of transparent Er-doped ZnO nano thin films prepared by sol–gel process

In this study, rare earth element (Er) doped ZnO nano thin films which have dual structure of (Zn1−xErx)O (x = 0.0, 0.01, 0.02, 0.03, 0.04 and 0.05) are prepared by using sol–gel method. The microstructure and electrical properties of prepared nano thin films are investigated. Nano thin films are coated on the glass substrate by using the dip coating method. The films are annealed at 600 °C for 30 min. The X-ray diffractometer (XRD), scanning electron microscopy and atomic force microscopy are used to determine the structural properties such as crystal structures, grain sizes, surface morphology; Hall effect measurements system is used to investigate the electrical properties of materials. XRD results showed that all Er doped nano thin films have a hexagonal structure and (002) orientation. Surface morphologies of ZnErO thin films are denser and more uniform than the undoped ZnO thin film. According to the Hall effect measurements, the resistivity of the films decreased with increasing Er concentration from $$0$$ to $$4\%$$ and then slightly increased at $$5\% Er$$ .

Characterisation of Cs ion implanted GaN by DLTS

Deep level transient spectroscopy (DLTS) was used to characterise Cs implanted GaN grown by hydride vapour phase epitaxy (HVPE). This implantation was done at room temperature using energy of 360keV to a fluence of 10–11cm−2. A defect with activation energy of 0.19eV below the conduction band and an apparent capture cross section of 1.1 × 10–15cm2 was induced. This defect has previously been observed after rare earth element (Eu, Er and Pr) implantation. It has also been reported after electron, proton and He ion implantation.

Effect of Rare Earth Er on the Microstructure and Mechanical Properties of High Temperature Titanium Alloys

The microstructures and mechanical properties of the high temperature titanium alloys containing Er, i.e. Ti-6Al-2.5Sn-4Zr-0.3Mo-1Nb-0.35Si-xEr (x=0, 0.1, 0.3wt%), were investigated. Both the grain size and lamellar structure inside grains were significantly refined with the addition of Er in as-cast alloys. Lamellar and duplex microstructures were obtained after forging and heat treatment. Silicide precipitates were generated in the boundary of lamellar α phase after aging treatment. Meanwhile, a few α2 phase were precipitated in the alloys after aging treatment. After 600°C /100h thermal exposure, the α2 phases with a mean size of 7nm and spacing of 10 nm were precipitated homogeneously in α lamellar. The creep properties were significantly improved by the addition of rare earth Er due to the formation of the second phase containing Er, silicide and α2 phase.

Properties of sputtered ZnS and ZnS:A (A = Er, Yb) films grown at low substrate temperatures

Radio-frequency magnetron sputtering was used to deposit ZnS thin films doped with rare earth elements (Er and Yb) on glass substrates at two different temperatures (room temperature and 180 °C). The crystal structure, surface morphology, and optical properties of the deposited films were studied as a function of the deposition variables as a first step in the possible application of lanthanide-doped ZnS as buffer layer and/or window layer in thin film photovoltaic devices. From the x-ray diffraction patterns, it was found that the samples have preferred orientation depending on the substrate temperature and on the doping level. Moreover, optical constants were determined from spectroscopic ellipsometry measurements and found that samples of undoped ZnS, in particular, exhibit optical constants that are in good agreement with those reported in the literature for the two ZnS crystalline phases. The band gap (Eg) was calculated using the extinction coefficient (k), which was reduced according to the degree of doping. Also, based on ultraviolet-visible spectroscopy measurements, it was determined that the films have a transmittance of 80% for wavelengths above 350 nm, and a shift of the absorption edge to longer wavelengths when the degree of doping was increased. Finally, photoluminescence measurements were performed at room and low temperature using below bandgap excitation to probe defect states within the gap, as well as the luminescent characteristics of the Er3+ and Yb3+ ions in the ZnS host.

Er addition to Al-Si-Mg-based casting alloy: Effects on microstructure, room and high temperature mechanical properties

Abstract The paper deals with the production, heat treatment, microstructural and mechanical characterization of innovative Al-Si-Mg alloys based on Al-7Si-0.4 Mg (A356) with additions of rare earth Er, with the aim of increasing the microstructural stability and mechanical performances at high temperature. Three alloys with different Er concentration (between 0, and 0.41 wt%) were investigated in the as-cast, peak aged and overaged conditions. Microstructural analyses demonstrated that Er additions affect eutectic morphology by fragmenting and spheroidising Si particles. Tensile tests at RT, 423 and 473 K proved that Er-containing alloys have improved mechanical strength with respect to the reference alloy; in particular, among the investigated alloy, the one with 0.22 wt% Er displayed the best combination of mechanical properties in all the tested conditions. Additions of 0.41 wt% Er, on the other hand, led to reduced castability of the alloy, with increased fraction of casting defects, and to the formation of primary Er-rich precipitates with high aspect ratio, causing a drop in ductility and reduced mechanical properties. Tests results demonstrated the importance of suitable chemical additions in improving the mechanical behaviour of cast Al-Si-Mg alloys. It can be concluded that the alloy containing 0.22 wt% Er could be proposed for structural applications at room and elevated temperatures, effectively extending the operating temperatures of Al-Si-Mg-based alloys.

Effect of Rare Earth Er on Microstructure and Mechanical Properties of Cast Al-Si-Mg Alloy

It is well known that Al-Si-Mg alloy can form Chinese script eutectic Mg2Si and large blocky primary Mg2Si phases. In this paper, the microstructures and mechanical properties of cast Al-18Si-10Mg-xEr (x=0, 0.3, 0.5, 0.8 and 1.0 wt.%) alloy were investigated. The as-cast samples were characterized by optical microscopy (OM), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) with wavelength dispersive spectroscopic (WDS). The results show that the morphology of primary Mg2Si changed from large block or Chinese script-like to fine block with increasing of Er contents from 0.3% to 1.0%., and the morphology of eutectic Si phases transformed into fine coral-like fibrous structure and the size of eutectic Si dramatically decrease. The mechanical properties were researched by tester with different concentration of rare earth Er. It was found that the ultimate tensile strength and hardness increased by 32.1% and 21.4%, respectively.

Thermal and corrosion behavior of as cast Al[sbnd]Si alloys with rare earth elements

Aluminum silicon based alloys are the most important commercial casting alloys. Their cast microstructure is strongly related to their technical properties. By adding other selected alloying elements, the alloy microstructure is known to be modified, thus improving its desired properties. Rare earths (RE) can be used as alloying elements to achieve better technical performance of AlSi based alloys.In this work, the effects of individual RE (La, Pr, Nd, Sm, Gd, Tb, Dy or Er) addition on a hypoeutectic as cast AlSi alloy were studied. In order to investigate the correlation between microstructure changes and thermal and corrosion behavior, the microstructure of the samples and of the intermetallic phases was examined by scanning electron microscopy, electron microprobe analysis, and X-ray powder diffraction. Differential thermal analysis was performed to determine ternary eutectic reaction temperature. A similar decrease in eutectic temperature was recorded for all AlSi-RE samples. Decreased hardness due to RE addition was shown by Vickers hardness measurements. DC polarization potentiodynamic measurements showed that RE addition increased corrosion resistance in 3.5 wt% NaCl solution.

Leaching rare-earth and radioactive elements from alkaline rocks of the Lovozero Massif, Kola Peninsula

The paper presents data on the leaching efficiency of rare-earth (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) and radioactive (Th and U) elements by various reagents from alkaline rocks of the Lovozero Massif. Element concentrations were analyzed by ICP-MS and instrumental neutral activation (INAA). A new complex technique is suggested for analyzing elements on the solid phase of polymer hydrogels. This technique makes it possible to enhance the sensitivity and selectivity of INAA when these elements are simultaneously contained in rocks. Data are presented on the selective leaching of trace elements and the application of environmentally safe reagents.

Metal-Organic Frameworks Modulated by Doping Er(3+) for Up-Conversion Luminescence.

Here we present metal-organic frameworks prepared by a one-step synthesis method, possessing both architectural properties of MOF building and up-conversion luminescence of rare earth Er(3+) (hereafter denoted as Up-MOFs). Up-MOFs have characteristic up-conversion emissions at 520, 540, and 651 nm under the excitation of 980 nm owing to the multiple photon absorption. The up-conversion mechanism of these Up-MOFs has been discussed, and it can be attributed to the excited state absorption process. The design and synthesis of Up-MOF materials possessing near-infrared region excitation and up-conversion luminescence are fully expected to be candidates for the advancement of applications in bioimaging, sensors, optoelectronics, and energy conversion/storage devices.

Determination of rare earth and concomitant elements in magnesium alloys by inductively coupled plasma optical emission spectrometry

An Inductively Coupled Plasma Optical Emission Spectrometry method for simultaneous determination of Al, Ca, Cu, Fe, In, Mn, Ni, Si, Sr, Y, Zn, Zr and rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) in magnesium alloys, including the new rare earth elements-alloyed magnesium, has been developed. Robust conditions have been established as nebulizer argon flow rate of 0.5mLmin−1 and RF incident power of 1500W, in which matrix effects were significantly reduced around 10%. Three acid digestion procedures were performed at 110°C in closed PFA vessels heated in an oven, in closed TFM vessels heated in a microwave furnace, and in open polypropylene tubes with reflux caps heated in a graphite block. The three digestion procedures are suitable to put into solution the magnesium alloys samples. From the most sensitive lines, one analytical line with lack or low spectral interferences has been selected for each element. Mg, Rh and Sc have been studied as internal standards. Among them, Rh was selected as the best one by using Rh I 343.488nm and Rh II 249.078nm lines as a function of the analytical lines. The trueness and precision have been established by using the Certified Reference Material BCS 316, as well as by means of recovery studies. Quantification limits were between 0.1 and 9mgkg−1 for Lu and Pr, respectively, in a 2gL−1 magnesium matrix solution. The method developed has been applied to the commercial alloys AM60, AZ80, ZK30, AJ62, WE54 and AE44.

Influence of Rare-Earth (Doped) on Low-Density Bi<sub>1.6</sub>Pb<sub>0.4</sub>Sr<sub>2</sub>Ca<sub>1.9</sub>RE<sub>0.1</sub>Cu<sub>3</sub>O<sub>δ </sub>(RE=Nd, Er) Superconductors via Co-Precipitation Method

Effect of Ca doped by rare-earth elements, Nd and Er (x=0.10) on the structural and transport properties of low density Bi1.6Pb0.4Sr2Ca1,9RE0.1Cu3Oδ (RE=Nd,Er) samples have been investigated. The samples have been prepared via co-precipitation (COP) method from precipitate of saturated solutions of metal acetates, iso-propanol solution and oxalic acid. The metal oxalates powder was subjected to thermal treatment of 24 hours calcination at 845oC and mixed with 0.10 g sucrose C12H22O11 which is used as supplementary filler. The pelletized powder was heated for 2 hours at 400 oC and sintered for at 850oC for 48 hours. All samples show a single step transition in the R-T curves. The critical current density (Jc) and transition temperature (Tczero) for both Nd and Er doped with x = 0.10 were found to be lower than standard samples. Tczero obtained varies between 98 K and 66 K. XRD data showed the decrease of volume fraction for the Bi-2223 phase and increase of the volume fraction Bi-2212 phase with the doping of Nd and Er.

High-quality c-axis oriented non-vacuum Er doped ZnO thin films

Preparation, growth, structure and optical properties of high-quality c-axis oriented non-vacuum Er doped ZnO thin films were studied. Zn1−xErxO (x=0.0, 0.01, 0.02, 0.04, and 0.05) precursor solutions were prepared by sol–gel synthesis using Zn, and Er based alkoxide which were dissolved into solvent and chelating agent. Zn1−xErxO thin films with different Er doping concentration were grown on glass substrate using sol–gel dip coating. Thin films were annealed at 600°C for 30min, and tried to observe the effect of doping ratio on structural and optical properties. The particle size, crystal structure, surface morphologies and microstructure of all samples were characterized by X-Ray diffraction (XRD) and Scanning Electron Microscope (SEM). The UV–vis spectrometer measurements were carried out for the optical characterizations. The surface morphology of the Zn1−xErxO films depend on substrate nature and sol–gel parameters such as withdrawal speed, drying, heat treatment, deep number (film thickness) and annealing condition. Surface morphologies of Er doped ZnO thin films were dense, without porosity, uniform, crack and pinhole free. XRD results showed that, all Er doped ZnO thin films have a hexagonal structure and (002) orientation. The optical transmittance of rare earth element (Er) doped ZnO thin films were increased. The Er doped ZnO thin films showed high transparency (>85) in the visible region (400–700nm).

A nuclear targeted dual-photosensitizer for drug-resistant cancer therapy with NIR activated multiple ROS.

Photodynamic therapy against cancer, especially multidrug resistant cancer, is limited seriously due to the efflux of photosensitizer molecules by P-glycoprotein, which leads to insufficient production of reactive oxygen species (ROS). For the purpose of abundant ROS generation and effective therapeutic response, herein, we firstly design and fabricate a nuclear targeted dual-photosensitizer for photodynamic therapy against multidrug resistant cancer. Molecule-photosensitizer Ce6 was selected and modified on the surface of core/shell structure nano-photosensitizer upconversion@TiO2 and then nuclear targeted peptides TAT were anchored for nuclear targeting. Through selective doping of rare earth elements Er and Tm, multiple ROS (˙OH, O2˙-, and 1O2) can be generated for the dual-photosensitizer and realize their functions synergistically using a single 980 nm NIR excitation. The nano-sized photosensitizer accompanied with nuclear targeting can effectively generate multiple ROS in the nucleus regardless of P-glycoprotein and directly break DNA double strands, which is considered as the most direct and serious lesion type for cytotoxic effects. Therefore, enhanced photodynamic therapy can be achieved against multidrug resistant cancer. In vitro and in vivo studies confirmed the excellent therapeutic effect of the dual-photosensitizer against cancer cells and drug-resistant cancer cells, as well as xenograft tumor models.

Hard Magnetic Properties and Thermal Stability for TbCu<sub>7</sub>-Type SmCo<sub>6.4</sub>Si<sub>0.3</sub>Zr<sub>0.3</sub> Alloys With Sm Substituted by Various Rare-Earth Elements

The magnetic properties and thermal stability of melt spun SmCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6.4</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> ribbons with various rare-earth (RE) elements substituted for Sm have been investigated. It is verified that the properties’ combination of SmCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> -based ribbons can be modified by selected RE substitution. The light RE Ce is beneficial for enhancing the saturation magnetization and the remanence, while the coercivity and thermal stability can be significantly improved by heavy REs Gd, Ho, and Er substitutions. The highest room-temperature coercivity of 1467 kA/m was achieved in the Sm <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</sub> Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6.4</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> ribbon. For the temperature range of 27 °C–200 °C, Gd is the best element for enhancing the thermal stability, and the optimal temperature coefficients <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> are −0.032%/°C and −0.269%/°C, respectively. For the range of 27 °C–400 °C, Ho is the best element to improve the thermal stability, and the values of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> are −0.064%/°C and −0.19%/°C, respectively.

Distribution and fractionation of the rare earth elements in Brazilian soils

The distribution and fractionation of Sc, Y and 14 rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) were investigated in 144 samples (topsoil and subsoil) from 88 sites distributed across Brazil. Although, a wide range of natural variability in REE content was observed, overall the REE median contents were relatively low compared with those reported in soils from other parts of the world. The REE contents in Brazilian soils showed significant correlation mainly with Fe, Mn and Ti oxides, as well as organic matter. REE distribution in soils basically depend on the parent material, while fractionation of individual REEs depend on soil characteristics that are partly influenced by pedogenic process. Soils developed from alkaline igneous rocks showed the highest average content of REEs followed by sedimentary rocks, unconsolidated clay sediments, metamorphic rocks, basic igneous rocks, unconsolidated sand and silt sediments, and acid igneous rocks. REE normalized patterns varied significantly within each geological formation, except for soils derived from alkaline igneous rocks. The greatest variations were observed in the light REEs. Graphic inspection using exploratory data analysis tools such as Q–Q normal plots and boxplots was effective to recognize patterns and identify different data groups, determine threshold values and thus define the range of the background REE variability. The data set generated in this study may be used as a preliminary reference for regulatory actions in the Brazilian environmental legislation.

Electronic and optical properties of Er doped in AlN

Using density functional theory combined [Formula: see text] method, the structural, electronic and optical properties of rare earth Er substituted Al atom [Formula: see text] and its complex with neighboring N vacancy [Formula: see text]-[Formula: see text] in wurtzite AlN were investigated, respectively. Calculated results show that both defects induced quite localized [Formula: see text]-[Formula: see text] related defect donor levels in the band gap but had few effects on host electronic structures. Moreover, the calculated complex dielectric functions and other optical constants show that these two defects show clear bulk optical properties, only a small peak near the redshift edge appears for the complex defect. These results show that Er dopant AlN should be a good optical material candidate for optoelectronics application.

Effect of Er doping on the superconducting properties of porous MgB 2

MgB2 bulk sample with porous structure was produced by using the in-situ solid-state reaction method under argon (Ar) atmosphere of 10 bar. Elemental Er in powder form was doped into MgB2 with different compositions (Mg 1−x Er x )B2, where x=0.00, 0.03 and 0.05, in order to investigate the effect of rare-earth (RE) element Er on the structural and electromagnetic properties of porous MgB2. The Er-doped samples result in small grain size structure compared to the undoped one. The lattice constants a and c of the doped samples, determined from X-ray diffraction (XRD) analysis, increase with the increasing Er content, and consequently the superconducting transition temperature (Tconset) of MgB2, determined from resistivity measurements, is slightly suppressed. Also, the upper critical field (B c2), the irreversibility field (B irr) and the critical current density (J c) values are significantly enhanced in the doped samples. For the best sample (x=0.03), at 15 K under a magnetic field of 4 T, the J c value reaches 2.4 ×104 A cm−2, which is higher than that of the porous sample by an order of 103, and the B irr value at 20 K reaches 9.7 T. These results imply that the RE element Er fills the pores, enhances the density and the grain connectivity. Hence, the superconducting properties of the porous MgB2 sample improve by Er doping.

Observation of efficient population of the red-emitting state from the green state by non-multiphonon relaxation in the Er3+–Yb3+ system

AbstractThe rare earth Er3+ and Yb3+ codoped system is the most attractive for showcasing energy transfer upconversion. This system can generate green and red emissions from Er3+ under infrared excitation of the sensitizer Yb3+. It is well known that the red-emitting state can be populated from the upper green-emitting state. The contribution of multiphonon relaxation to this population is generally considered important at low excitation densities. Here, we demonstrate for the first time the importance of a previously proposed but neglected mechanism described as a cross relaxation energy transfer from Er3+ to Yb3+, followed by an energy back transfer within the same Er3+–Yb3+ pair. A luminescence spectroscopy study of cubic Y2O3:Er3+, Yb3+ indicates that this mechanism can be more efficient than multiphonon relaxation, and it can even make a major contribution to the red upconversion. The study also revealed that the energy transfers involved in this mechanism take place only in the nearest Er3+–Yb3+ pairs, and thus, it is fast and efficient at low excitation densities. Our results enable a better understanding of upconversion processes and properties in the Er3+–Yb3+ system.