Rare-earth Solubility Research Articles

Broadband NIR emission from rare earth doped-SiO2-Nb2O5 and SiO2-Ta2O5 nanocomposites

The rising demand for more efficient telecommunication networks that can carry larger data volume is currently one of the most pressing technological challenges. In this sense, developing new materials to obtain NIR broadband emission is an urgent matter. We have successfully prepared Tm3+/Yb3+ co-doped 70SiO2-30Nb2O5 and 70SiO2–30Ta2O5 (mol%) nanocomposites by the sol–gel method. The Tm3+/Yb3+ co-doped 70SiO2-30Nb2O5 and 70SiO2-30Ta2O5 nanocomposites displayed intense broad emission that extends from 1.6 to 2.1 µm, with maximum at 1.8 µm. The bandwidth values lied around 230 or 260 nm depending on the crystalline phase. Increasing rare earth content elicited discrete quenching, which attests to good rare earth solubility and distribution within the hosts. The luminescence results are outstanding in terms of silicate hosts and point to the potential application of these materials in optical amplifiers, remote sensing, and LIDAR systems.

Synthesis, structure, and magnetic properties of rare-earth-doped Ni0.75Zn0.25Fe2O4 nickel zinc ferrite

We have developed processes for the synthesis of Ni0.75Zn0.25Fe2–x Ln x O4 ferrite solid solutions with the spinel structure and investigated the effect of the rare-earth elements Nd, Gd, Yb, and Lu on the chemical composition, extent, lattice parameters, and magnetic properties of the solid solutions. The results demonstrate that rare-earth solubility in the parent spinel reaches ≈2.5 at %, which leads to changes in the magnetic characteristics of the material, in particular in its saturation magnetization M s, T C, and coercive force H c.

Electrolytic reduction of a simulated oxide spent fuel and the fates of representative elements in a Li2O-LiCl molten salt

A series of electrolytic reduction experiments were carried out using a simulated oxide spent fuel to investigate the reduction behavior of elements in a mixed oxide condition and the fates of elements in the reduction process with 1.0 wt% Li2O-LiCl. It was found out that 155% of the theoretical charge was enough to reduce the simulated. Te and Eu were expected to possibly exist in the precipitate and on the anode surface, whereas Ba and Sr showed apparent dissolution behaviors. Rare earths showed relatively low metal fractions from 28.2 to 34.0% except for Y. And the solubility of rare earths was observed to be low due to the low concentration of Li2O. The reduction of U was successful as expected showing 99.8% of a metal fraction. Also it was shown that the reduction of ZrO2 would be effective when a relatively small amount was included in a metal oxide mixture.

Low-Dimensional Network Formation in Molten Sodium Carbonate.

Molten carbonates are highly inviscid liquids characterized by low melting points and high solubility of rare earth elements and volatile molecules. An understanding of the structure and related properties of these intriguing liquids has been limited to date. We report the results of a study of molten sodium carbonate (Na2CO3) which combines high energy X-ray diffraction, containerless techniques and computer simulation to provide insight into the liquid structure. Total structure factors (Fx(Q)) are collected on the laser-heated carbonate spheres suspended in flowing gases of varying composition in an aerodynamic levitation furnace. The respective partial structure factor contributions to Fx(Q) are obtained by performing molecular dynamics simulations treating the carbonate anions as flexible entities. The carbonate liquid structure is found to be heavily temperature-dependent. At low temperatures a low-dimensional carbonate chain network forms, at T = 1100 K for example ~55% of the C atoms form part of a chain. The mean chain lengths decrease as temperature is increased and as the chains become shorter the rotation of the carbonate anions becomes more rapid enhancing the diffusion of Na+ ions.

Devitrification of Bi- and Ga-containing germanium-based chalcogenide glasses

Novel BixGay(GeSe4)50-(x+y)/2(GeTe4)50-(x+y)/2 glasses are proposed as perspective materials, having potential to combine thermo-electric effect, rare earth solubility, different types of conductivity and topological insulating behavior in one medium. Thermal stability and non-isothermal crystallization kinetics of these materials are studied by differential scanning calorimetry, X-ray diffraction and Raman scattering techniques. Crystallization of at least five different phases is assumed due to the fit of experimental DSC curves. The Dietzel criterion of glass stability is determined and the activation energy for each crystallization process is calculated. The applicability of Johnson–Mehl–Avrami (JMA) equation to describe the crystallization kinetics is verified in these glasses.

Silver metaphosphate glass wires inside silica fibers--a new approach for hybrid optical fibers.

Phosphate glasses represent promising candidates for next-generation photonic devices due to their unique characteristics, such as vastly tunable optical properties, and high rare earth solubility. Here we show that silver metaphosphate wires with bulk optical properties and diameters as small as 2 µm can be integrated into silica fibers using pressure-assisted melt filling. By analyzing two types of hybrid metaphosphate-silica fibers, we show that the filled metaphosphate glass has only negligible higher attenuation and a refractive index that is identical to the bulk material. The presented results pave the way towards new fiber-type optical devices relying on metaphosphate glasses, which are promising materials for applications in nonlinear optics, sensing and spectral filtering.

Fiber evanescent wave spectroscopy based on IR fluorescent chalcogenide fibers

Chalcogenide glasses, owing to their transparency in the infrared window and the appropriate solubility of rare earth, allows the generation of middle infrared (mid-IR) radiation from a near infrared or visible pumping source. These emitted mid-IR broad bands can probe the vibrational modes of several molecules, e.g. CH, CO or CCl. Relying on this principle, a mid-IR optical sensor using the mid-IR fluorescence of Pr3+: Ga-Ge-Sb-S fibers has been developed. The detection principle is based on Fiber Evanescent Wave Spectroscopy (FEWS). The spectroscopic characterization of praseodymium ions (Pr3+) was performed in the near and mid-IR and is discussed on the basis of comparison with Judd–Ofelt calculations. The broad emission spectrum of the Pr3+: Ga-Ge-Sb-S fiber from 4 to 5μm could enable the monitoring of multiple pollutants. In this study, chloroform detection is carried out via a novel technique derived from FEWS. In this way, an infrared sensor was developed, composed of a pumping source in near-IR, a mid-IR detector and a tapered Pr3+: chalcogenide fiber to enhance the detection sensitivity. These results demonstrate for the first time the feasibility of detecting molecules by FEWS using the mid-IR fluorescence emitted by rare earth ions doping chalcogenide fibers. This method is an effective alternative to the classical FEWS system, as RE doped chalcogenide fibers have the advantage of being a compact mid-IR source.

Doping silica beyond limits with laser plasma for active photonic materials

The limited solubility of rare-earths in silica hampers the development of loss-compensated photonic integrated circuits. We report a novel method using femtosecond laser plasma assisted hybrid material integration of rare-earth-doped tellurite with silica, achieving high doping concentration of Er3+ and Yb3+-ions, 1.63 × 1021 atoms.cm−3,without segregation validated by Er3+:4I13/2 lifetime of 9.1 ms. The sequential ablation of two individual rare-earth (Er3+/Yb3+) doped-tellurite glass targets produces an exceptional intermixing of Er3+ and Yb3+-ions extending to the pristine silica with sharp interface. Formation of such homogeneous glass structure with Er3+-Yb3+-ions in a matrix of silica is not possible to realise by conventional methods.

Ga–Sb–S Chalcogenide Glasses for Mid‐Infrared Applications

In this study, a novel chalcogenide glass system, Ga–Sb–S, is reported. The glass‐forming ability, the physical properties, and the structure are investigated; and the potential applications of the glasses are evaluated. The compositions consisting of ~3%–10% Ga, ~29%–37% Sb, and ~57%–63% S can form glasses. The glasses have a wide transparent window of ~0.8–14 μm, high linear refractive indices of ~2.62–2.70 (@10 μm), high third‐order nonlinear refractive indices of ~12.4 × 10−14 cm2/W (@ 1.55 μm), low phonon energy, and large rare earth solubility. These favorable properties make them promising materials for mid‐infrared applications such as thermal imaging, nonlinear optics, and lasers.

Measurement of chemical activities of rare earths (RE: Ce, Pr, Sm and Eu) in cadmium alloy

Activity of rare earth (RE) elements, Ce, Pr, Sm and Eu is measured in each of the cadmium rich binary alloys of RE, by making use of a molten salt based electrochemical cell. The binary alloy consists of a mixture of cadmium rich intermetallic compound and a liquid phase of known composition. Four independent cells are constructed; one for each of the rare earth elements and electromotive force (EMF) is measured as a function of temperature for each cell, respectively. Partial molar Gibbs energy of these rare earth metals in liquid cadmium is derived from the EMF output over a temperature range. Gibbs energy of formation of CeCd11, PrCd11, SmCd6 and EuCd11 are deduced from the measured EMF values and the reported literature data on the solubility of rare earth elements in liquid cadmium.

Study On The Separation And Extraction Of Rare-Earth Elements From The Phosphor Recovered From End Of Life Fluorescent Lamps

Abstract In this study, recovered phosphor from end of life three-wavelength fluorescent lamp was selected for reuse rare earth elements in the phosphor. The effect of a type of acid, concentration, and time was investigated as solubility of rare earth elements. In addition, precipitate heat-treated was investigated as possibility of reusable phosphor. The results showed that the amount of the rare earth elements was different values depending on the type of acid, and it was investigated with concentration of acid and reaction time. After precipitation reaction, the precipitate was sintered in electric furnace in order to reuse rare earth elements as phosphor. It was confirmed that yttrium, europium, oxygen, and carbon through X-ray diffraction and inductively coupled plasma analysis. Following the results, it can assume that rare earth oxide reuse the phosphor as three-wavelength fluorescent lamp.

Spectroscopic properties of Tb3 +-doped lead zinc phosphate glass for green solid state laser

This work reports the spectroscopic properties of a new Tb3+-doped zinc lead phosphate glass, prepared by a conventional melt-quenching technique. Glasses show good rare earth solubility and high thermal stability. Optical properties of the glasses are studied by absorption, photoluminescence excitation and emission spectroscopy and lifetime measurement. Several luminescence bands of Tb3+ ions are observed under 376nm excitation wavelength in 400–650nm spectral region. The green to blue intensity ratio increases by concentration of terbium ions up to 5mol%. The lifetime of the 5D4 excited state was found to be 2.70 to 2.54ms for low and high concentration of dopant ions, respectively. The strong green emission of the studied glasses with large experimental branching ratio highlights their capability as solid state green lasers.

Spectroscopic properties of 2.7 μm emission in Er3+ doped telluride glasses and fibers

Emissions at 2.7μm from telluride glasses with various Er2O3 doping concentrations are investigated. The prepared glasses have excellent thermostability and high rare-earth solubility. Judd–Ofelt parameters are calculated based on the absorption spectra. A large emission cross section (1.12×10−20cm2) and a high spontaneous radiative coefficient (57.8s−1) are obtained at 2.7μm. The fluorescence properties of glasses with different concentrations are analyzed and presented. An Er3+-doped fiber is fabricated via a rod-in-tube technique, and the loss at 1310nm is ∼2.1dB/m measured by using the cut-back method. Strong upconversion emission caused by intense pump absorption is observed from the Er3+doped fiber under excitation by a 980nm laser diode (LD).Telluride glasses with high Er3+ doping concentration and good thermal property are prepared. Energy transfer processes for 1.5μm, and 2.7μm, as well as visible emission are fully discussed. Enhanced 2.7μm emission is achieved from the bulk glass. An Er3+ doped fiber is successfully drawn, and strong upconversion emission is observed in the fiber.

Microstructures and mechanical properties of the age hardened Mg–4.2Y–2.5Nd–1Gd–0.6Zr (WE43) microalloyed with Zn

Abstract The effect of trace addition of 0.2 wt.% Zn on the microstructures and mechanical properties of the age-hardening Mg–4.2Y–2.5Nd–1Gd–0.6Zr (wt.%) (WE43) alloy has been investigated. As compared with the WE43 alloy after solid solution treatment at 525 °C, the block-like Zn–Zr phase was still observed in the WE43-0.2Zn alloy. However, the time for WE43-0.2Zn alloy to get peak hardness at 250 °C was two hours, a half earlier than that in WE43 alloy, meaning a accelerated age precipitation kinetics has been achieved due to the addition of 0.2 wt.% Zn. Microalloyed with 0.2 wt.% Zn enhanced the ultimate tensile strength (UTS) slightly and ductility significantly both in the solutionized and peak aged condition. The enhancement in strength and ductility is possible associated with the larger volume fraction of precipitation phases due to a reduction of the solubility of rare earth elements (RE) in the α-Mg matrix, the larger aspect ratio (length to width) of precipitates and a decrease in stacking fault energy by addition of Zn.

Material and technology trends in fiber optics

Abstract The increasing fields of applications for modern optical fibers present great challenges to the material properties and the processing technology of fiber optics. This paper gives an overview of the capabilities and limitations of established vapor deposition fiber preform technologies, and discusses new techniques for improved and extended doping properties in fiber preparation. In addition, alternative fabrication technologies are discussed, such as a powder-based process (REPUSIL) and an optimized glass melting method to overcome the limits of conventional vapor deposition methods concerning the volume fabrication of rare earth (RE)-doped quartz and high silica glasses. The new preform technologies are complementary with respect to enhanced RE solubility, the adjustment of nonlinear fiber properties, and the possibility of hybrid fiber fabrication. The drawing technology is described based on the requirements of specialty fibers such as adjusted preform and fiber diameters, varying coating properties, and the microstructuring of fiber configurations as low as in the nanometer range.

Spectroscopic Investigation and Crystallization Study of Rare Earth Metaborate Glasses

Besides their interesting optical properties, Rare Earths (RE) can be found abundantly as fission products at the end of the nuclear fuel cycle. After reprocessing, they are stored by dissolution in a borosilicate glassy matrix. RE are also used to simulate actinides when studying nuclear waste immobilization. It is very important to understand the environment of RE in such complex glasses. Moreover, composition changes can strongly affect RE solubility in the glass melt and RE-rich phases (such as RE- silicate apatite) can crystallize during cooling. As boron oxide seems to play an important role on the solubility of RE by preventing the crystallization of RE-rich phases, we focused our study on a system containing only B2O3 and RE2O3 (with RE= La or Nd), and more precisely on the RE-metaborate composition RE2O3.3B2O3. As this glass, which has a congruent crystallization, is thought to have a structure similar to the corresponding crystalline phase REB3O6, we intended to go further in the understanding of its structure using 11B MAS NMR, EXAFS at the Nd-LIII edge and optical absorption. The crystallization behavior of the glasses thermally treated was also studied using DTA, XRD and optical absorption.

Blue–Green Emission in Terbium‐Doped Alumina (Tb:Al2O3) Transparent Ceramics

AbstractAlumina (Al2O3) is one of the most versatile ceramics, utilized in an amazing range of structural and optical applications. In fact, chromium‐doped single crystal Al2O3was the basis for the first laser. Today, most photoluminescent (PL) materials rely on rare earth (RE) rather than transition‐metal dopants because RE doping produces greater efficiencies and lower lasing thresholds. RE‐doped alumina could provide an extremely versatile PL ceramic, opening the door for a host of new applications and devices. However, producing a transparent RE:Al2O3suitable for PL applications is a major challenge due to the very low equilibrium solubility of RE (∼10−3%) in Al2O3in addition to alumina's optical anisotropy. A method is presented here to successfully incorporate Tb3+ions up to a concentration of 0.5 at% into a dense alumina matrix, achieving a transparent light‐emitting ceramic. Sub‐micrometer alumina and nanometric RE oxide powders are simultaneously densified and reacted using current‐activated, pressure‐assisted densification (CAPAD), often called spark plasma sintering (SPS). These doped ceramics have a high transmission (∼75% at 800 nm) and display PL peaks centered at 485 nm and 543 nm, characteristic of Tb3+emission. Additionally, the luminescent lifetimes are long and compare favorably with lifetimes of other laser ceramics. The high transparencies and PL properties of these ceramics have exciting prospects for high energy laser technology.

Femtosecond laser induced structural changes in fluorozirconate glass

Fluorozirconate glasses, such as ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF), have a high infrared transparency and large rare-earth solubility, which makes them an attractive platform for highly efficient and compact mid-IR waveguide lasers. We investigate the structural changes within the glass network induced by high repetition rate femtosecond laser pulses and reveal the origin of the observed decrease in refractive index by using Raman microscopy. The high repetition rate pulse train causes local melting followed by rapid quenching of the glass network. This results in breaking of bridging bonds between neighboring zirconium fluoride polyhedra and as the glass resolidifies, a larger fraction of single bridging fluorine bonds relative to double bridging links are formed in comparison to the pristine glass. The distance between adjacent zirconium cations is larger for single bridging than double bridging links and consequently an expansion of the glass network occurs. The rarified glass network can be related to the experimentally observed decrease in refractive index via the Lorentz-Lorenz equation.

The Solubility of Rare Earth with Variable Valent and Electrochemical Behavior in LiCl–KCl–AlCl3 Melts

The solubility of RE2O3 (RE=Sm, Yb, and Eu) with variable valent in LiCl–KCl melts is extremely low. It is impossible to directly extract variable valent metals from RE2O3 using electrolysis in molten salts. After adding AlCl3 to the melt system, the solubility measurements of RE2O3 in LiCl–KCl and LiCl–KCl– AlCl3 melts indicate that AlCl3 can effectively chloridize RE2O3. Take Yb2O3 as an example, the solubility of Yb2O3 in the LiCl–KCl–AlCl3 melts increases first and decreases afterwards due to the rapid volatility of AlCl3 with increase of temperature. The thermodynamic calculation of the reaction of Yb2O3 and AlCl3 also indicates that the reaction would proceed forward at 753K. Electrochemical behavior of RE2O3 on a molybdenum electrode in LiCl–KCl melts containing AlCl3 also indicates that RE2O3 is effectively chloridized by AlCl3, and then discharges in the form of RE(III) ions in the cathode. The underpotential deposition of RE on pre-deposited aluminum leads to the formation of Al-RE alloy. The extraction of RE with variable valent from RE oxide in LiCl–KCl melts is proven to be feasible.

Organic species of lanthanum in natural environments: Implications to mobility of rare earth elements in low temperature environments

Abstract Naturally occurring organic ligands, such as acetate, citrate, malonate, oxalate, and succinate, play important roles in mobility and accumulation of La and other rare earth elements in low temperature systems under Earth surface conditions. However, a comprehensive and consistent thermodynamic database covering the complexes of rare earth elements with those naturally occurring organic ligands is lacking. In this study, thermodynamic data of organic species of rare earth elements (REE) represented by La, with an emphasis on their aqueous complexes with organic ligands, are critically reviewed. The organic ligands covered by this study include acetate, citrate, malonate, oxalate and succinate. In this critical review, the Specific Interaction Theory (SIT) model is adopted for extrapolation to infinite dilution. This model is a reliable activity coefficient model valid for a wide range of ionic strengths. These critically reviewed data, including complex formation constants, SIT interaction coefficients and solubility product constants, would enable accurate modeling of the speciation and solubility of REE in various environments including high ionic strength environments, providing insight into mobility and enrichment of REE in various environments.