Rare earth metal-containing ionic liquids

As an innovative tool, ionic liquids (ILs) are widely employed as an alternative, smart, reaction media (vs. traditional solvents) offering interesting technology solutions for dissolving, processing and recycling of metal-containing materials. The costly mining and refining of rare earths (RE), combined with increasing demand for high-tech and energy-related applications around the world, urgently requires effective approaches to improve the efficiency of rare earth separation and recovery. In this context, ionic liquids appear as an attractive technology solution. This review addresses the structural and coordination chemistry of ionic liquids comprising rare earth metals with the aim to add to understanding prospects of ionic liquids in the chemistry of rare earths

Controlling Magnetism via Transition Metal Exchange in the Series of Intermetallics Eu(T1,T2)5In (T = Cu, Ag, Au)

Three series of intermetallic compounds Eu(T1,T2)5In (T = Cu, Ag, Au) have been investigated in full compositional ranges. Single crystals of all compounds have been obtained by self-flux and were analyzed by single X-ray diffraction revealing the representatives to fall into two structure types: CeCu6 (oP28, Pnma, a = 8.832(3)–9.121(2) Å, b = 5.306(2)–5.645(1) Å, c = 11.059(4)–11.437(3) Å, V = 518.3(3)–588.9(2) Å3) and YbMo2Al4 (tI14, I4/mmm, a = 5.417(3)–5.508(1) Å, c = 7.139(2)– 7.199(2) Å, V = 276.1(2)–285.8(1) Å3). The structural preference was found to depend on the cation/anion size ratio, while the positional preference within the CeCu6 type structure shows an apparent correlation with the anion size. Chemical compression, hence, a change in cell volume, which occurs upon anion substitution appears to be the main driving force for the change of magnetic ordering. While EuAg5In shows antiferromagnetic behavior at low temperatures, mixing Cu and Au within the same type of structure results in considerable changes in the magnetism. The Eu(Cu,Au)5In alloys with CeCu6 structure show complex magnetic behaviors and strong magnetic field-induced spin-reorientation transition with the critical field of the transition being dependent on Cu/Au ratio. The alloys adopting the YbMo2Al4 type structure are ferromagnets exhibiting unusually high magnetic moments. The heat capacity of EuAu2.66Cu2.34In reveals a double-peak structure evolving with the magnetic field. However, low-temperature X-ray powder diffraction does not show a structural transition

Sustainable Urban Mining of Critical Elements from Magnet and Electronic Wastes

A straightforward and environment-friendly process for acid-free leaching of rare-earth elements and cobalt, which are critical materials, from waste magnet materials has been developed. The process also allows for selective leaching of rare-earth elements from magnet-containing electronic wastes, such as end-of-life hard disk drives and electric motors. The use of copper salts eliminates the use of volatile toxic acids in the dissolution and separation processes, which allows for a more eco-friendly approach to recovering critical elements and a safer work environment. Recovered critical materials were shown to be suitable for reinsertion into the materials supply chain

Room temperature synthesis of β-NaGdF4:RE3+ (RE = Eu, Er) nanocrystallites and their luminescence

A roomtemperaturesynthesiswasdevelopedforphasepure β-NaGdF4 nanocrystallitesaswellas5,10, and 20%Eu3þ or 5%Er3þ doped material.RareearthacetatesandNaClreactina1:2Mratiowitha variableexcessofNH4F inethyleneglycolwithin24hours.Sincethethermodynamicstabilityofthe hexagonalphasedecreasesalongthelanthanideseries,alargerexcessofNH4F wasrequiredforthe synthesis ofluminescentsamplesdopedwiththesmallerEr3þ ions thanforEu3þ doped orpure β- NaGdF4. ThematerialswerecharacterizedbypowderX-raydiffraction,electronmicroscopy,andlumi- nescence spectroscopy.TheEu3þ-doped samplesshow 5D0-7FJ and 5D1-7FJ luminescence afterEu3þ excitationat394nmorGd3þ excitationat273nmand308nm.Theratioof 5D1 vs. 5D0 luminescence is influenced bytheexcitationwavelengthandtheEu3þ concentration. TheEr3þ-doped samplesshow green andredupconversionluminescence,respectively,fromthe 2H11/2þ4S3/2-4I15/2 and 4F9/2-4I15/2 transitions after970nmexcitation

Anomalous effects of Sc substitution and processing on magnetism and structure of (Gd1−xScx)5Ge4

The kinetic arrest observed in the parent Gd5Ge4 gradually vanishes when a small fraction (x = 0.025, 0.05 and 0.10) of Gd is replaced by Sc in (Gd1−xScx)5Ge4, and the magnetic ground state changes from antiferromagnetic (AFM) to ferromagnetic (FM). A first order phase transition coupled with the FM-AFM transition occurs at TC = 41 K for x = 0.05 and at TC = 53 K for x = 0.10 during heating in applied magnetic field of 1 kOe, and the thermal hysteresis is near 10 K. The first-order magnetic transition is coupled with the structural Sm5Ge4-type to Gd5Si4-type transformation. The magnetization measured as a function of applied magnetic field shows sharp metamagnetic-like behavior. At the same time, the AFM to paramagnetic transition in (Gd1−xScx)5Ge4 with x = 0.10, is uncharacteristically broad indicating development of strong short-range AFM correlations above the Néel temperature. Comparison of the magnetization data of bulk, powdered, and metal-varnish composite samples of (Gd0.95Sc0.05)5Ge4 shows that mechanical grinding and fabrication of a composite have little effect on the temperature of the first-order transformation, but short-range ordering and AFM/FM ratio below TC are surprisingly strongly affected

Ternary Polar Intermetallics within the Pt/Sn/R Systems (R = La− Sm): Stannides or Platinides?

Starting generally with a 4:6:3 molar ratio of Pt, Sn, and R (where R = La–Sm), with or without the application of a NaCl flux, seven ternary compounds were obtained as single crystals. The platinides Pt4Sn6R3 (R = La–Nd) crystallize with the Pt4Ge6Pr3 type of structure (oP52, Pnma, a = 27.6–27.8 Å, b = 4.59–4.64 Å, c = 9.33–9.40 Å). With R = Pr, Pt4Sn6Pr3–x (oP52, Pnma, a = 7.2863(3) Å, b = 4.4909(2) Å, c = 35.114(1) Å) is also obtained, which might be considered a high-temperature polymorph with disorder on the Sn- and Pr-sites. For R = Nd and Sm, a structurally related isostructural series with a slightly different composition Pt3Sn5R2–x (oP52, Cmc21, a = 4.50–4.51 Å, b = 26.14–26.30 Å, c ≈ 7.29 Å) has been observed, together with Pt7Sn9Sm5 (oS42, Amm2, a = 4.3289(5) Å, b = 28.798(4) Å, c = 7.2534(9) Å) under the same conditions. The latter exhibits the rare Zr5Pd9P7-type structure, linking polar intermetallics to metal phosphides, in accord with P7Pd9Zr5≡Pt7Sn9Sm5. All structures may be described in terms of either negative Pt/Sn networks encapsulating positive R atoms, or {PtSnx} clusters (x = 5, 6, or rarely 7) sharing vertices and edges with R in the second coordination sphere and with considerable heterometallic Pt–R bonding contributions

Ferromagnetic cluster-glass phase in Ca(Co1-xIrx)(2-y)As-2 crystals

Single crystals of Ca(Co1−xIrx)2−yAs2 with 0≤x≤0.35 and 0.10≤y≤0.14 have been grown using the self-flux technique and characterized by single-crystal x-ray diffraction (XRD), energy-dispersive x-ray spectroscopy, magnetization M, and magnetic susceptibility χ measurements versus temperature T, magnetic field H, and time t, and heat-capacity Cp(H,T) measurements. The XRD refinements reveal that all the Ir-substituted crystals crystallize in a collapsed-tetragonal structure as does the parent CaCo2−yAs2 compound. A small 3.3% Ir substitution for Co in CaCo1.86As2 drastically lowers the A-type antiferromagnetic (AFM) transition temperature TN from 52 to 23 K with a significant enhancement of the Sommerfeld electronic heat-capacity coefficient. The A-type AFM structure consists of ab-plane layers of spins ferromagnetically aligned along the c axis with AFM alignment of the spins in adjacent layers along this axis. The positive Weiss temperatures obtained from Curie-Weiss fits to the χ(T\u3eTN) data indicate that the dominant magnetic interactions are ferromagnetic (FM) for all x. A magnetic phase boundary is inferred to be present between x=0.14 and x=0.17 from a discontinuity in the x dependencies of the effective moment and Weiss temperature in the Curie-Weiss fits. FM fluctuations that strongly increase with increasing x are also revealed from the χ(T) data. The magnetic ground state for x≥0.17 is a spin glass as indicated by hysteresis in χ(T) between field-cooled and zero-field-cooled measurements and from the relaxation of M in a small field that exhibits a stretched-exponential time dependence. The spin glass has a small FM component to the ordering and is hence inferred to be comprised of small FM clusters. The competing AFM and FM interactions along with crystallographic disorder associated with Ir substitution are inferred to be responsible for the development of a FM cluster-glass phase. A logarithmic T dependence of Cp at low T for x=0.14 is consistent with the presence of significant FM quantum fluctuations. This composition is near the T=0 boundary at x≈0.16 between the A-type AFM phase containing ferromagnetically-aligned layers of spins and the FM cluster-glass phase

R3Au9Pn (R = Y, Gd-Tm; Pn = Sb, Bi): A Link between Cu10Sn3 and Gd14Ag51

A new series of intermetallic compounds R3Au9Pn (R = Y, Gd-Tm; Pn = Sb, Bi) has been discovered during the explorations of the Au-rich parts of rare-earth-containing ternary systems with p-block elements. The existence of the series is strongly restricted by both geometric and electronic factors. R3Au9Pn compounds crystallize in the hexagonal crystal system with space group P63/m (a = 8.08-8.24 \uc5, c = 8.98-9.08 \uc5). All compounds feature Au-Pn, formally anionic, networks built up by layers of alternating edge-sharing Au@Au6 and Sb@Au6 trigonal antiprisms of overall composition Au6/2Pn connected through additional Au atoms and separated by a triangular cationic substructure formed by R atoms. From a first look, the series appears to be isostructural with recently reported R3Au7Sn3 (a ternary ordered derivative of the Cu10Sn3-structure type), but no example of R3Au9M is known when M is a triel or tetrel element. R3Au9Pn also contains Au@Au6Au2R3 fully capped trigonal prisms, which are found to be isostructural with those found in the well-researched R14Au51 series. This structural motif, not present in R3Au7Sn3, represents a previously unrecognized link between Cu10Sn3 and Gd14Ag51 parent structure types. Magnetic property measurements carried out for Ho3Au9Sb reveal a complex magnetic structure characterized by antiferromagnetic interactions at low temperature (TN = 10 K). Two metamagnetic transitions occur at high field with a change from antiferromagnetic toward ferromagnetic ordering. Density functional theory based computations were performed to understand the materials' properties and to shed some light on the stability ranges. This allowed a better understanding of the bonding pattern, especially of the Au-containing substructure, and elucidation of the role of the third element in the stability of the structure type