Interaction Of Rare Earth Ions Research Articles

Atomic-level insights into the adsorption of rare earth Y(OH)3-nn+ (n = 1–3) ions on kaolinite surface

The interaction of rare earth elements (REEs) ions with clay minerals is crucial for understanding the processing of mineralization, extraction and recovery of ion-adsorption rare earth. Theoretical studies based on density functional theory (DFT) were performed to investigate the adsorption of rare earth Y(OH)3-nn+ (n = 1–3) ions on kaolinite surfaces of varying deprotonation degree depending on the solution pH. The Conductor-like Screening Model (COSMO) was used to simulate the water environment of adsorption. The calculated results showed that the surface electrostatic potential and frontier orbital are enhanced and increasingly localized around the exposed oxygen atoms with the increase of the deprotonation degree of kaolinite (0 0 1) surface hydroxyls. Y(OH)3-nn+ ions are adsorbed mainly via the Y atom and the surface O atoms, and located over the center of Al-hexagonal ring on kaolinite (0 0 1) surface, and the center of Si-hexagonal ring on kaolinite (0 0 −1) surface. The adsorption energies increase with the increase of deprotonation degree of kaolinite (0 0 1) surface, and decrease with the increase of the hydrolysis degree of Y3+. The results of Mulliken bond length and population, atomic charge, electron density and density of states (DOS) revealed that Y(OH)3-nn+ ions interact with kaolinite (0 0 1) surface through the combination of covalent and electrostatic bonding, while with (0 0 −1) surface mainly through electrostatic bonding. The above calculated results would provide some atomic-level insights for the interaction of rare earth ions with kaolintie surfaces in aqueous solution.

Specific features of thermal and magnetic properties of YbB50 at low temperatures

Heat capacity, thermal expansion, and magnetization of ytterbium boride $\mathrm{Yb}{\mathrm{B}}_{50}$ were studied at temperatures 0.6--300 K, 5--300 K, and 2--300 K, respectively. We revealed two smooth peaks at about 4.0 and 60 K in the temperature dependence of the heat capacity. A comparison with the heat capacity of the diamagnetic isostructural boride $\mathrm{Lu}{\mathrm{B}}_{50}$ shows that these anomalies can be attributed to excitations in the ytterbium sublattice (Schottky anomalies). A scheme for splitting of the ground $^{2}F_{7/2}$ multiplet of $\mathrm{Y}{\mathrm{b}}^{3+}$ ions in the crystal field is proposed. Reliability of the proposed crystal-field energies of the $\mathrm{Y}{\mathrm{b}}^{3+}$ ions is confirmed by the analysis of temperature dependencies of magnetic susceptibility and magnetization in applied magnetic fields up to 55 kOe. A clear anisotropy of the thermal expansion and a negative expansion within a wide temperature range (40--185 K) were observed. Assuming that this anomaly of the thermal expansion in higher borides is caused by the specific thermal evolution of a crystal lattice observed earlier, in particular, in $\mathrm{Lu}{\mathrm{B}}_{50}$, and the interaction of rare-earth ions with lattice strains, we have determined phenomenological Gr\uneisen parameters which characterize effects due to thermal transitions of $\mathrm{Y}{\mathrm{b}}^{3+}$ ions between the ground and excited states. A phase transition of $\mathrm{Yb}{\mathrm{B}}_{50}$ to any magnetically ordered state was not observed down to the lowest temperatures of experiments.

Electronic and Magnetic Investigations of Rare-Earth Tm-doped AlGaN Ternary Alloy

Electronic structure and magnetic interaction of substitutional thulium rare earth-doped wurtzite Al0.5Ga0.5N ternary alloy have been performed using density-functional theory within local spin-density approximation with Hubbard-U corrections (LSDA+U) approach. The LSDA+U method is applied to the rare earth (RE) 4f states. The calculation of formation energy shows that it is more energetically favorable for a substitutional Tm atom to replace the Al atom than the Ga atom. For AlGaN:Tm, the lattices parameters are expanded due to larger ionic radius of Tm than that of Al atoms. The energy band gap of AlGaN:Tm has direct character and its width becomes small compared with that of AlGaN. The magnetic coupling between Tm ions in the nearest neighbor sites is ferromagnetic. Magnetic interaction of rare earth ion with the host states at the valence and conduction band edges has been investigated and compared to those of GaN:Mn and has been found to be relatively small.

Modified absorption attributes of neodymium doped magnesium-zinc-sulfophosphate glass

Rare-earth doped glass systems with improved absorption and emission features are greatly demanding for diverse applications. In this endavour, selection of right glass host, modifier, rare earth ions with optimized composition is the key issue. This communication reports the conventional melt-quench synthesis of neodymium (Nd3+) doped magnesium-zinc- sulfophosphate glass system of the form (60-x)P2O5-20MgO-20ZnSO4-xNd2O3 (x = 0, 0.5, 1, 1.5, 2.0 and 2.5 mol%). The influence of varying Nd3+ contents on the physical (density, molar volume, molar refractivity, refractive index and electronic polarizability) and absorption properties of the prepared glass system is determined. The amorphousity of the obtained samples is confirmed by XRD analysis. The glass refractive indices (ranged from 1.85 to 1.90) and densites (between 2.63 to 2.77 g.cm-3) are found to increase with increasing concentration of Nd3+ ion. Furthermore, the energies associated with the direct and indirect optical transitions across the forbidden gap are observed to reduce with the increase of Nd3+ ion concentration. Meanwhile, the increase of Urbach energy with increasing Nd3+doping is ascribed to the interaction of rare earth ions with the ligands of the glass network and subsequent transformation of weak bonds into defects. The room temperature UV–Vis-NIR spectra revealed eleven absorption band corresponding to the transitions from the ground state to various excited states of the Nd3+ ion. Incorporation of Nd3+ ion is discerned to enhance the glass absorbance appreciably together with the alteration of physical properties. Present findings may be beneficial for the advancement of Nd3+ ions doped magnesium-zinc-sulfophosphate glass system based photonic devices especially for infrared solid state laser.

Effect of Design and Rare-Earth Doping of the Structural, Optical, Electrical and Light Emitting Properties of Si-Based Superlattices Developed for Photonic Application

Nowadays, silicon-based nanostructures attract great attention due to their wide functionality. However, in spite of a lot of efforts forwarded on the investigation of Si-based nanomaterials, additional research is still required in order to design their optical properties for optoelectronic, photovoltaic or memory applications. The structural disorder is one of the main issues that may reduce the efficiency of device operation in the applications area of every nanomaterial. Undoped and rare-earth (RE) doped Si-rich-SiO2 (SiOx) composite films and multilayers were recently investigated [1-3]. An efficient RE emission was achieved in Er- and, later, Nd-doped SRSO films due to an interaction of RE ions with Si-nanoclusters (Si-ncs). Although, a multilayer (ML) approach offers a precise control of Si-ncs distribution via a tuning of SRSO thickness, RE-doped SRSO-based MLs are not well addressed. This work presents the benefits of ML approach to achieve high efficiency and to control RE emission from Nd-doped SiOx/SiNx-based MLs grown by RF magnetron sputtering. Their properties were studied by means of XRD, TEM, PL and PL excitation methods versus deposition conditions, annealing treatment and ML design (doping, thickness of alternated sublayers (silicon oxide, nitride)). In each type of ML structures, either one or both sublayers were doped with Nd ions to investigate the effect of selective or full doping on PL emission. The results will be summarized and compared with those of Nd-doped SiOx/SiO2 MLs. It will be showed that comparable Nd PL emission can be obtained for both types of ML structures. Besides, fabrication approach allowed the PL emission to be achieved from as-grown samples. However, the highest Nd PL intensity was obtained after an annealing at about 700°C in nitrogen flow, whereas the formation of crystallized Si-ncs occurs at 1000-1100°C. The mechanism of Nd ions' excitation (i.e. an interaction with Si-ncs as well as with matrix defects, if any) will be discussed in details based on PL excitation spectra and PL life-time data. These results reveal potential photonic applications of Nd-doped MLs. This work was supported by French National Agency (ANR) through DAPHNES project. 1. Pratibha Nalini R., Khomenkova L., Debieu O., Cardin J., Dufour C., Carrada M., Gourbilleau F.,Nanoscale Research Letters, 7, 124 (2012). 2. Cueff S., Labbé C., Khomenkova L., Jambois O., Pellegrino P., Garrido B., Frilay C., Rizk R., Mater. Sci. Eng. B. 177, 725 (2012). 3. E. Talbot, R. Lardé, P. Pareige, L. Khomenkova, K. Hijazi, F. Gourbilleau, Nanoscale research letters 8, p.39 (8 pages) (2013).

Spectroscopic in situ examination of interactions of rare earth ions with humic substances

This study utilized the methods of fluorescence quenching and differential absorbance to probe in situ the extent and the nature of the interactions between rare earth ions (REIs) and humic substances. Experiments were conducted with the standard Suwannee river humic acid (SRHA) in the presence of varying amount of lanthanum, europium and terbium. The data of differential absorbance showed that the mechanism of SRHA-metal complexation was largely the same for all the examined REIs. In all cases several discrete bands whose properties were discerned via numerical decomposition of the differential spectra absorbance were observed. Their nature was examined based on the comparison of the experimental data and those of NICA-Donnan modeling carried out for Eu3+. The observed effects suggested that the changes of SRHA absorbance induced by REIs binding are likely to be caused by a bathochromic shift of the absorbance bands associated with such chromophores. The intensity of the Gaussian band with a maximum at 387 nm was observed to be proportional to the total concentration of SRHA-bound REIs. The data obtained in this study demonstrate the existence of complex yet quantifiable changes of the spectroscopic properties of humic species in the presence of REIs and their utility to quantify modes of interactions in such systems.

The study of Raman spectrum, distortion of lattice and spin reorientation phase transition on Pr doped DyFeO3 system

Pr doped rare-earth orthoferrites DyFeO3 is synthesized by solid state reaction. X-ray diffraction shows that the lattice parameters of Dy1-xPrxFeO3increase and distortion of lattice decreases with Pr content x increasing. Raman spectroscopy reveals that the change of effective mass (meff) [meff=xmPr+(1-x)mDy] together with lattice structure change results in the shift of vibration modes. With the increase of Pr content, Raman modes of wave number less than 200 cm-1 remain constant, but the modes of wave number greater than 200 cm-1 decrease with Pr content increasing (except the mode B3u near 420 cm-1). The weak ferromagnetic ordering, created by Dzyaloshinsky-Moriya interaction, is reduced with doping level increasing. The interaction of rare earth ions with Fe3+ ion, together with the change of lattice distortion, results in the increasing of spin reorientation phase transition temperature when xx increasing to over 0.3.

Forms of rare earth elements’ sorption by quartz and goethite in the presence of bacteria Rhodopseudomonas palustris

The adsorption of a mixture of 16 isotopes of 14 rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) present in the initial solution in equal concentrations by quartz and goethite in the presence of bacteria Rhodopseudomonas palustris was studied under different acidity conditions. The solution pH was apparently the leading factor in the interaction of rare earth ions with the surface of mineral and biological sorbents. These interactions were controlled by electrostatic forces in acid (pH 4) and neutral (pH 7) solutions; the precipitation of elements from the solution was the predominant mechanism under alkaline conditions (pH 9). Microorganisms affected the adsorption of lanthanides by quartz in the entire pH range under study, especially at pH 7. In the presence of bacteria, the adsorption of the elements studied by goethite increased in an acid solution, remained unchanged under neutral conditions, and slightly decreased under alkaline conditions. Microorganisms increased the concentration of nonexchangeable forms of the elements adsorbed on the surface of quartz and goethite, which could be due to the formation of low-soluble complexes of rare earth elements with organic substances produced by bacteria.

Application of symmetry groups of four-dimensional space in spectroscopy of crystals

A method of classification of many-electron states that involves symmetry groups of four-dimensional space is developed. Taking into account the spatial and temporal symmetry, the selection rules for electric and magnetic dipole transitions are investigated. The reduction relations for the irreducible representations of the orthogonal group O4 and the group R4 of pure rotations of the four-dimensional space on the groups and Oh4 and O4 of the four-dimensional cube and of the octahedron on the three-dimensional groups Oh and D6h of the cubic and hexagonal systems, respectively, are obtained. The four-dimensional classification of the levels of the spin-orbit interaction of rare earth ions for the intermediate reduction on the group of the four-dimensional cube is performed. With the help of the irreducible representations of the O4 group, the selection rules of magnetic and forbidden electric dipole transitions, as well as of intercombination transitions, are investigated.

Synthesis of new types of complexes by the interaction of rare earth ions with sodium sulfide in solid state in presence of sun light

New complexes of the type [Ln (SH)(OH) 2(H 2O)] have been synthesized in solid state in presence of sun light by the interaction of Na 2S.7H 2O with Ln= La, Ce, Pr, Nd and Sm]. Similar complexes have also been synthesized by the mixing solution of LnCl 3 with sodium sulfide in room light. The complexes of Pr, Nd and Sm are paramagnetic. The complex of Nd prepared in solid state has an hexagonal structure coexisting with a tetragonal structure, while the complex prepared in solution has a pure hexagonal structure with lattice constant, a = 4.061 A o and c = 6.345 A o . The presence of SH, OH and H 2O moieties in coordination sphere was confirmed by I.R. and TGA — DTA. The UV-visible spectra show weak and sharp f-f transitions.

Interaction of rare earth ions doped in nanocrystals embedded in amorphous matrices with two-level systems of the matrix

The interactions of rare earth ions doped in nanoparticles with the amorphous matrix in which they are embedded are studied with hole burning and fluorescence line narrowing techniques. The results suggest that at low temperatures the homogeneous broadening of optical transitions of the rare earth ions are dominated by interactions with the two-level systems of amorphous matrix. At higher temperatures other phonon-induced processes which are seen in bulk single crystals dominate the dynamics.

Langmuir-Blodgett Films of Fullerene Containing β-Diketone Derivatives and Their Coordination Complexes with Rare Earth Metal Ions

Two new fullerene-containing β-diketone derivatives are synthesized. Their Langmuir and Langmuir-Blodgett (LB) films are prepared on water and rare earth metal ion solution subphases. The π-A isotherms, UV-Vis and XPS spectra indicate the interaction of rare earth ions with β-diketone moieties.

Exchange Polarization and the Magnetic Interactions of Rare Earth Ions

Exchange Polarization and the Magnetic Interactions of Rare Earth Ions

Exchange Polarization and the Magnetic Interactions of Rare Earth Ions

Received 13 February 1961DOI:https://doi.org/10.1103/PhysRevLett.6.277©1961 American Physical Society

The interaction of rare earth ions with diethylenetriaminepentaacetic acid

The interactions of rare earth ions with diethylenetriaminepentaacetic acid have been investigated by potentiometric procedures. Metal chelate formation constants have been calculated and compared with those defining similar interactions with ethylenediaminetetraacetic acid and N-hydroxyethylethylenediaminetriacetic acid.