Properties Of Lanthanides Research Articles

Mimicking the magnetic properties of rare earth elements using superatoms

Rare earth elements (REs) consist of a very important group in the periodic table that is vital to many modern technologies. The mining process, however, is extremely damaging to the environment, making them low yield and very expensive. Therefore, mimicking the properties of REs in a superatom framework is especially valuable but at the same time, technically challenging and requiring advanced concepts about manipulating properties of atom/molecular complexes. Herein, by using photoelectron imaging spectroscopy, we provide original idea and direct experimental evidence that chosen boron-doped clusters could mimic the magnetic characteristics of REs. Specifically, the neutral LaB and NdB clusters are found to have similar unpaired electrons and magnetic moments as their isovalent REs (namely Nd and Eu, respectively), opening up the great possibility in accomplishing rare earth mimicry. Extension of the superatom concept into the rare earth group not only further shows the power and advance of this concept but also, will stimulate more efforts to explore new superatomic clusters to mimic the chemistry of these heavy atoms, which will be of great importance in designing novel building blocks in the application of cluster-assembled nanomaterials. Additionally, based on these experimental findings, a novel "magic boron" counting rule is proposed to estimate the numbers of unpaired electrons in diatomic LnB clusters.

Critical assessment and optimization of phase diagrams and thermodynamic properties of RE–Zn systems – Part II – Y–Zn, Eu–Zn, Gd–Zn, Tb–Zn, Dy–Zn, Ho–Zn, Er–Zn, Tm–Zn, Yb–Zn and Lu–Zn

All available phase diagram and thermodynamic data for the Y–Zn, Eu–Zn, Gd–Zn, Tb–Zn, Dy–Zn, Ho–Zn, Er–Zn, Tm–Zn, Yb–Zn and Lu–Zn systems have been collected and critically assessed. Optimized model parameters for the thermodynamic properties of all phases have been obtained. Trends in the properties of the rare earth (RE)–Zn systems as one traverses the rare earth series have been exploited for purposes of estimating missing data and for checking existing data for consistency.

Critical assessment and optimization of phase diagrams and thermodynamic properties of RE–Zn systems-part I: Sc–Zn, La–Zn, Ce–Zn, Pr–Zn, Nd–Zn, Pm–Zn and Sm–Zn

All available phase diagram and thermodynamic data for the Sc–Zn, La–Zn, Ce–Zn, Pr–Zn, Nd–Zn, Pm–Zn and Sm–Zn systems have been collected and critically assessed. Optimized model parameters for the thermodynamic properties of all phases have been obtained. Trends in the properties of the rare earth (RE)–Zn systems as one traverses the rare earth series have been exploited for purposes of estimating missing data and for checking existing data for consistency.

Fractal approach to BaTiO3-ceramics micro-impedances

A new approach, based on fractal geometry and correlation between microstructure–nanostructure and rare-earth properties and other additives doped BaTiO3-ceramics and electronics properties, is applied. The grain contacts geometry based on different stereological models and especially intergranular contact surface fractal morphology was the subject of several papers of these authors. The main conclusion was that intergranular capacities have higher values then expected which is induced by contact surfaces sizes augmentation as a consequence of their fractal nature. Bigger micro-capacities were justified by virtually having bigger dielectric constants which was achieved by introducing fractal correction factor α0>1, as a multiplier to the usual dielectric constant εr to gain a bigger value of α0εr. In further BaTiO3-ceramics micro-electronics fractal theory development, different fractal methods were used to describe complexity of the spatial distribution of BaTiO3-grains, as well as pores. This led to a fractal correction factor revisited model, which considers existence of surfaces fractality, pores fractality and the inner liquid dynamics and solid state sintering phase within ceramics material represented by the Brownian motion model. The new correction factor α is a function of these three ceramics fractality “sources”. Here, the relationship between α and α0 is established for doped BaTiO3-ceramics using the Curie–Weiss law and temperature as an omnipresent sintering parameter. Also, the model of two grains contact impedance is studied for different α and frequency values. Ву the control of shapes and contact surfaces numbers on the entire BaTiO3-ceramic sample level, the control over structural properties of these ceramics can be achieved, with the aim of correlation between material electronic properties and corresponding microstructure. The fractal nature for analysis of the ceramics structure provides a new approach for modeling and prognosis of the grain shape and relations between the BaTiO3-ceramic structure, micro- and nano-, and all other electronic properties in the light of new frontier for higher level electronic circuits integration.

Processes and Technologies for the Recycling of Spent Fluorescent Lamps

Abstract The growing industrial application of rare earth metals led to great interest in the new technologies for the recycling and recovery of REEs from diverse sources. This work reviews the various methods for the recycling of spent fluorescent lamps. The spent fluorescent lamps are potential source of important rare earth elements (REEs) such as: yttrium, terbium, europium, lanthanum and cerium. The characteristics of REEs properties and construction of typical fl uorescent lamps is described. The work compares also current technologies which can be utilized for an efficient recovery of REEs from phosphors powders coming from spent fluorescent lamps. The work is especially focused on the hydrometallurgical and pyrometallurgical processes. It was concluded that hydrometallurgical processes are especially useful for the recovery of REEs from spent fluorescent lamps. Moreover, the methods used for recycling of REEs are identical or very similar to those utilized for the raw ores processing.

ChemInform Abstract: Layered Rare Earth Hydroxides (LREHs): Synthesis and Structure Characterization Towards Multifunctionality

AbstractReview: 52 refs.

Geochemical properties of rare earth elements (REE) in coals of Abyek coalfield, North Iran

In Iran, coal deposits from the upper Triassic-lower Jurassic era are limited to the Tabas and Alborz coal basins and three small independent carboniferous regions. One of the coalfields in the Alborz basin is the Abyek coalfield, the focus of our investigation. It is located in the northern mountain ranges of Iran, and we investigate the geochemical behavior of the rare earth elements in it. Five samples were collected and analyzed for trace and rare earth elements (REE) using inductively coupled plasma (ICP). The Abyek area is characterized by very high ash value. The content of total REY (REEs + Y) in the coals varies from 143.19 to 254.39 ppm and ranged 28–43.83 ppm in argillite. The abundance of light rare earth elements (LREES) is higher relative to heavy rare earth elements (HREEs).

Life Cycle Impact of Rare Earth Elements

The diverse properties of rare earth elements have seen broad and growing applications in clean energy technologies, hybrid vehicles, pollution control, optics, refrigeration, and so on. This study presents a “cradle-to-gate” life cycle assessment of the energy use, resource depletion, and global warming potential resulting from the production of rare earth elements (REEs) using the Bayan Obo rare earth operation in Inner Mongolia, China, as a representative system. The study aggregates data from the literature, LCI databases, and reasonable estimations. A novel economic value-based allocation method for the multiple coproducts of the process is proposed. It is found that four of the high priced REEs scandium, europium, terbium, and dysprosium have very high GWPs from production relative to the rest. A mass-based allocation is also provided for comparison. Impacts on immediate local environment from waste streams that can be toxic are not included in this study.

The Importance of Rare Earth Contribution from Nodulizing Alloys and their Subsequent Effect on the Inoculation of Ductile Iron

The unique properties of rare earth elements (REE) have made them crucial to a number of emerging and growing technologies [medical diagnosis equipment, critical military-based technologies, catalysts, computers, magnets, hybrid cars, windmills etc.] increasing their demand, and strategic importance. Recently, increased demand has led to supply problems, with corresponding price fluctuations and difficulties in obtaining REE for use in the cast iron industry.

(Invited) Rare Earth Doped Metal-Oxide-Semiconductor Structures: A Promising Material System or a Dead End of Optoelectronic Evolution?

Integrated photonics is a key technology of the 21st century, and the electrically driven, integrated light emitter is an important building block, but difficult to realize. Thus, an enormous variety of different materials and material systems have been investigated in the past, ranging from the various approaches to integrate III-V semiconductors to the different types of Si-based light emission. Within the latter group rare earth (RE) implanted MOS structures feature a high conformity with standard CMOS processes combined with the excellent optical properties of RE elements.After more than 20 years of intense research in the field of Si-based light emission the results are mixed. With respect to important key parameters, most of all power efficiency, Si-based light emitters are not yet able to compete with their counterparts based on compound or organic semiconductors. The present contribution discusses the problems of Si-based light emitters at the example of RE-doped MOS structures, and compares various light emitter designs and their potential to overcome these problems.In detail, the power efficiency, the operation lifetime and the operation voltage of Tb- and Er-doped MOS structures are investigated. The main electroluminescence excitation mechanism is impact excitation of hot electron which plays an ambivalent role: efficient excitation is often related with efficient defect creation. In addition, a dark zone close to the injecting interface limits the scalability towards low voltages. The excitation mechanism und thus the performance of the light emitter is affected by the structure and composition of the dielectric stack of the MOS structure. Within this study, several host materials for the RE ions, namely stoichiometric and Si-rich silicon oxide or silicon nitride; different fabrication methods, namely plasma enhanced chemical vapour deposition, ion implantation and atomic layer deposition; and the use of additional buffer or injection layers are investigated. Finally, a short perspective to potential applications is given.

Rare earths supply chains: Current status, constraints and opportunities

The unique properties of rare earth elements (REEs) and lack of alternatives for their application in modern technologies, especially electronics and fast growing green technologies such as renewable energy generation and storage, energy efficient lights, electric cars, and auto catalysts, as well as specific military and aerospace applications, underpin their strategic status.The absolute domination of China in the production of REEs, aggravated by a significant reduction in export quotas since 2010, raised severe concerns of securing REE supply in the USA, Japan, European Union and other countries. In 2010–2012 it resulted in skyrocketing prices and supply deficit for most REEs, leading to numerous new REE start-up companies around the world, with allocation of large investments in additional geological explorations and technology development. At the same time, the supply difficulties enforced the downstream users of REEs to invest in the development of recycling technologies and reuse options for these elements.The main focus of this paper is to overview existing and emerging REE supply chains outside of China up to date (end of 2013), define their environmental constraints and opportunities, as well as reflect on a broader range of technical, economic, and social challenges for both primary production and recycling of REEs. A better understanding of these factors could help to optimize the supply chain of virgin and recycled rare earths, minimise the environmental impacts arising from their processing, and be used as a prototype for a broader range of critical metals and commodities.

Improving photocatalytic activity for hydrogen evolution over ZnIn2S4 under visible-light: A case study of rare earth modification

A series of rare earth (RE) ions (La3+, Ce3+, Gd3+, Er3+ or Y3+) modified ZnIn2S4 photocatalysts (RE-ZnIn2S4) were prepared using the hydrothermal method and characterized by various analysis techniques, such as UV–Vis diffusive reflectance spectroscopy, X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller surface analyzer, photoluminescence spectroscopy and X-ray photoelectron spectroscopy. The results indicated that the RE element exists as the oxide RE2O3 and their modification can reduce ZnIn2S4 crystallite size, inhibit ZnIn2S4 grain growth, promote ZnIn2S4 crystallite self-organization into a micro-sphere flower-like morphology, increase ZnIn2S4 surface area and total pore volume, and bring rich defects to ZnIn2S4. The photocatalytic activities of RE-ZnIn2S4 were evaluated based on photocatalytic hydrogen production from water under visible-light irradiation and the hydrogen production efficiency increased by 46%, 53%, 61%, 69%, and 106% after adding 2.0 wt% of Y, Gd, Er, Ce and La, respectively. The relationship between the photocatalytic activity of RE-ZnIn2S4 and the RE properties was discussed.

Energy Transfer from Sn2+ to RE3+ Cations in ZnO–P2O5 Glass

Abstract The photoluminescence (PL) properties of rare earth (RE)-doped SnO–ZnO–P2O5 (RE-SZP) glass were examined in the visible region. RE-SZP glass, except for those doped with Ce3+, exhibited similar optical band edges because of the s–p transition in Sn2+. The RE3+ PL excitation bands in RE-SZP glass were red-shifted compared to the bands in Sn-free glass because of the energy transfer from the Sn2+ center. In addition, the emission intensity in a few RE-SZP glass systems was remarkably enhanced by Sn2+ addition. Emission decays of Sn2+ in the glass were typically independent of the RE3+, and suggest the exchange interaction between Sn2+ and RE3+. This indicated that the RE3+ cation is generally located close to the Sn2+ center in order to allow energy transfer.

Synthesis and photoluminescence properties of Eu3+, Sm3+ and Pr3+ doped Ca2ZnWO6 phosphors for phosphor converted LED

In this work, we report on the synthesis and photoluminescence (PL) properties of rare earth (Eu3+, Sm3+ and Pr3+) doped double perovskite tungstate Ca2ZnWO6 phosphor. The phosphors were synthesized by two step modified solid state method. Phase purity and formation of phosphor were confirmed by XRD technique. PL spectra of Eu3+, Sm3+ and Pr3+ doped phosphor show intense emission peaks in red region at 615, 604 and 650nm respectively, upon the visible excitation of 466nm (Eu3+), 410nm (Sm3+) and 491nm (Pr3+). The CIE coordinates of the phosphors are in the yellow (Sm3+ doped sample) and orange (Eu3+ and Pr3+ doped sample) regions near the edge of color space which confirms their applicability in LEDs.

Lanthanides in the frame of Molecular Magnetism

Molecular magnetism is producing new types of materials which cover up to date aspects of basic science together with possible applications. This article highlights recent results from the point of view of lanthanides which are now intensively used to produce single molecule magnets, single chain and single ion magnets. After a short introduction reminding the main steps of development of molecular magnetism, the basic properties of lanthanides will be covered highlighting important features which are enhanced by the electronic structure of lanthanides, like spin frustration and chirality, anisotropy and non collinear axes in zero and one dimensional materials. A paragraph of conclusions will discuss what has been done and theperspectives to be expected.

The synthesis, structure and physical properties of lanthanide(III) complexes with nicotinic acid

Abstract This article reports the synthesis of novel, rare-earth coordination complexes with nicotinic acid. Three compounds with the general formula Ln2[(C5H4NCOO)6(H2O)4] (Ln = Yb, 1; Ln = Gd, 2; Ln = Nd, 3) were prepared from relatively cheap and readily available reactants. Their compositions and structure were characterized by IR spectroscopy and single-crystal X-ray diffraction. The magnetic and thermogravimetric properties were also studied. The complexes consist of centrosymetric, dimeric molecules having all six nicotinato ligands coordinated with the central atom in the bidentate mode. The coordination environment of the Ln3+ for all three compounds is 8. Here we describe the crystal structure of Yb and Gd complexes with nicotinic acid.

희토류 선광/정제 공정 중 발생된 오염원의 특성 및 처리기술

본 연구에서는 희토류의 특성과 자연에 부존하는 광상에 따른 선광 및 정제(분해침출/분리정제)공정 중 발생된 오염원 특성 및 처리기술에 대한 연구를 수행하였다. 연구결과 상업적으로 중요한 희토류광물은 이온흡착광, 탄산염계열의 바스트네사이트 및 인산염계열의 모나자이트이다. 이온흡착광의 선광공정은 황산암모늄을 이용한 용출 및 1,000에서 하소 과정이며, 바스트네사이트와 모나자이트의 선광공정은 파쇄/분쇄, 비중/자력선별 및 부유선별과정이다. 또한 분해침출/분리정제 공정은 산/알칼리 분해침출, P507(<TEX>$C_{16}H_{35}O_3P$</TEX>)/옥살산(<TEX>$H_2C_2O_4$</TEX>)을 이용한 분리정제 및 탄산화와 하소과정을 통한 정제과정이었다. 이 중 선광공정에서 발생한 오염원은 중금속, 불소, 황산염, 비소 및 방사성물질을 함유하는 광미이며, 분해침출/분리정제과정에서 발생하는 오염원은 유해가스 (HF, <TEX>$NO_x$</TEX>, <TEX>$SO_x$</TEX>, CO)와 방사성 광물찌꺼기, 그리고 중금속, 불소, 암모늄, 방사성물질(Th, U), 유기물 등을 함유하는 폐수이다. 유해가스는 산/알칼리 흡수탑을 이용하여 처리하며, 방사성 광물찌꺼기는 건조 후 밀폐보관하고, 폐수처리공정은 중금속, 불소 및 방사성물질의 경우 화학적 침전, 암모늄이온의 경우 stripping, struvite 침전, 그리고 유기물은 산화공정으로 처리한다. 보다 경제적이고 운영이 용이한 처리기술로 입상 알칼리제를 활용한 화학적 침전과 미량의 방사성물질 제거를 위한 입상 광산배수 슬러지 흡착공정을 제안한다. In this study, it was observed that the characteristics of pollutants produced during the processes of ore dressing and purification depends on the properties of rare earth and deposits from natural resources. The commercially important rare earth minerals discerned in this study were ion adsorption deposit, carbonate bastnasite and phosphate monazite. The ore dressing process for ion adsorption deposit elution was done by use of ammonium sulfate and calcination, while the process for bastnasite and monazite was smashing/grinding, gravity/magnetic separation and flotation. The process of decomposition/separation is mainly adopted for the purification process of rare-earth oxide by acid/alkali, P507 (<TEX>$C_{16}H_{35}O_3P$</TEX>)/oxalicacid (<TEX>$H_2C_2O_4$</TEX>) and carbonation and calcination. At the ore dressing process, dominant water pollutants were heavy metals, fluoride, sulphate, arsenic, and radioactive compounds, while purification process generally produced harmful gases (HF, <TEX>$NO_x$</TEX>, <TEX>$SO_x$</TEX>, CO), radioactive tailings and wastewater with heavy metals, fluoride, ammonium, radioactive materials (Th, U), and organic pollutants. Harmful gases were specifically generated from acid/alkali decomposition process while organic pollutants were originated from separation/purification process. To treat wastewater, chemical precipitation could be applied to remove heavy metal, fluoride and radioactive compounds, and stripping and struvite precipitation treated ammonium ions, while oxidation treated organic compounds.

Enhancement of Anion Binding in Lanthanide Optical Sensors

In the design of molecular sensors, researchers exploit binding interactions that are usually defined in terms of topology and charge complementarity. The formation of complementary arrays of highly cooperative, noncovalent bonding networks facilitates protein-ligand binding, leading to motifs such as the "lock-and-key". Synthetic molecular sensors often employ metal complexes as key design elements as a way to construct a binding site with the desired shape and charge to achieve target selectivity. In transition metal complexes, coordination number, structure and ligand dynamics are governed primarily by a combination of inner-sphere covalent and outer-sphere noncovalent interactions. These interactions provide a rich variable space that researchers can use to tune structure, stability, and dynamics. In contrast, lanthanide(III)-ligand complex formation and ligand-exchange dynamics are dominated by reversible electrostatic and steric interactions, because the unfilled f shell is shielded by the larger, filled d shell. Luminescent lanthanides such as terbium, europium, dysprosium, and samarium display many photophysical properties that make them excellent candidates for molecular sensor applications. Complexes of lanthanide ions act as receptors that exhibit a detectable change in metal-based luminescence upon binding of an anion. In our work on sensors for detection of dipicolinate, the unique biomarker of bacterial spores, we discovered that the incorporation of an ancillary ligand (AL) can enhance binding constants of target anions to lanthanide ions by as much as two orders of magnitude. In this Account, we show that selected ALs in lanthanide/anion systems greatly improve sensor performance for medical, planetary science, and biodefense applications. We suggest that the observed anion binding enhancement could result from an AL-induced increase in positive charge at the lanthanide ion binding site. This effect depends on lanthanide polarizability, which can be established from the ionization energy of Ln(3+) → Ln(4+). These results account for the order Tb(3+) > Dy(3+) > Eu(3+) ≈ Sm(3+). As with many lanthanide properties, ranging from hydration enthalpy to vaporization energy, this AL-induced enhancement shows a large discrepancy between Tb(3+) and Eu(3+) despite their similarity in size, a phenomenon known as the "gadolinium break". This discrepancy, based on the unusual stabilities of the Eu(2+) and Tb(4+) oxidation states, results from the half-shell effect, as both of these ions have half-filled 4f-shells. The high polarizability of Tb(3+) explains the extraordinarily large increase in the binding affinity of anions for terbium compared to other lanthanides. We recommend that researchers consider this AL-induced enhancement when designing lanthanide-macrocycle optical sensors. Ancillary ligands also can reduce the impact of interfering species such as phosphate commonly found in environmental and physiological samples.

Surface characterisation of fergusonite

There is currently very little information on the physico–chemical properties of rare earth element bearing minerals, or on their processing. With the increasing demand for rare earths, this is something that needs to be addressed. This paper introduces some surface chemistry analysis of fergusonite (YNbO4), and the bubble particle attachment. Zeta potential measurements indicate adsorption of sodium oleate and, to a lesser degree, potassium amyl xanthate onto the surface, and an increase in attachment to an air bubble is observed at pH 4·5 and 6·5. At a pH of 10·5, no attachment is observed, whether in the presence of the reagents or not. This analysis, although initial, will be used to initiate flotation tests, in order to facilitate the selective recovery of fergusonite. Two extensively characterised minerals, one hydrophilic (quartz) and one hydrophobic (galena) were also investigated as a comparison.Il y a présentement très peu d’information concernant les propriétés physico-chimiques des minéraux porteurs d’élément de terre rare, ou de leur traitement. Avec l’augmentation de la demande des terres rares, on a besoin d’examiner cette question. Cet article introduit une certaine analyse de la chimie de surface de la fergusonite (YNbO4) et de l’attachement de bulle-particule. Des mesures du potentiel zêta indiquent l’adsorption d’oléate de sodium et, à un degré moindre, du xanthate amyle de potassium à la surface. On observe également une augmentation de l’attachement à une bulle d’air à un pH de 4·5 et de 6·5. À un pH de 10·5, il n’y a pas d’attachement, que ce soit avec ou sans agents réactifs. Cette analyse, bien qu’initiale, sera utilisée pour initier des essais de flottation afin de faciliter la récupération sélective de la fergusonite. On a également examiné, à titre de comparaison, deux minéraux caractérisés considérablement, soit un hydrophile (quartz) et un hydrophobe (galène).

Electrochemical and thermodynamic properties of lanthanides (Nd, Sm, Eu, Tm, Yb) in Alkali metal chloride melts

Electrochemical and thermodynamic properties of Nd, Sm, Eu, Tm, and Yb chlorides in melts of individual LiCl, NaCl, KCl, and CsCl, of 3LiCl-2KCl, LiCl-KCl-CsCl, NaCl-KCl-CsCl, and NaCl-2CsCl eutectics, and of the equimolar NaCl-KCl mixture in the temperature interval 573–1173 K were studied by stationary and nonstationary methods. The mechanism of reduction of lanthanide(III) ions to metal was elucidated, and the main kinetic and thermodynamic characteristics of the process in alkali metal chloride melts were calculated. The influence of the ionic potential and polarizing power on the behavior of lanthanides in molten salts of various cationic compositions was determined.