Yb Compounds Research Articles

Temperature and pressure dependences of Sm valence in intermediate valence compound SmB6

We report the results of the X-ray absorption spectroscopy (XAS) on the intermediate valence compound SmB6. The XAS measurements were performed near the nonmagnetic-magnetic phase boundary. Mean Sm valence vSm was estimated from absorption spectra, and we found that vSm near the boundary (P≥10GPa and T∼12K) is far below a trivalent state with magnetic characteristics. Although the result is markedly different from the cases of pressure induced magnetic orders in Yb and Ce compounds, it is likely that the large deviation from the trivalent state seems to be common in some Sm compounds which possess electronic configuration between 4f5 and 4f6 with multi 4f electrons.

Yb3+-Activated inorganic aprotic liquids for diode-pumped lasers

This paper presents experimental data on the solubility of Yb(III) compounds in POCl3–MCl x , SOCl2–MCl x , and SO2Cl2–GaCl3 binary aprotic solvents (where MClx is a Lewis acid). We have measured the absorption and luminescence spectra of Yb3+ in the solutions thus prepared. Liquid POCl3–MCl4–Yb3+ (M = Zr or Sn), SOCl2–GaCl3–Yb3+, and SO2Cl2–GaCl3–Yb3+ gain media with [Yb3+] > 0.2 mol/L and an Yb3+ luminescence quantum yield η > 0.5 for diode-pumped lasers have been prepared for the first time.

DFT studies of thermoelectric properties of R–Au intermetallics at 300 K

Thermoelectric and electronic properties of cubic bi-intermetallics R–Au (R = Tb, Ho, Er, Tm and Yb) compounds were explored. Electronic properties i.e. density of states and band structure were computed using first principles calculations which proved the metallic nature of these compounds. Post-DFT (BoltzTraP) calculations were carried out to explore their thermoelectric properties like electrical conductivities, Seebeck coefficient, electronic thermal conductivities and figure of merit. The highest Seebeck coefficient and figure of merit were found for YbAu among these compounds which are 105 μV/K and 0.285 respectively. All the calculations were carried out at 300 K. Large values of figure of merit obtained for these compounds at room temperature indicate that these materials can be used for thermoelectric devices however need experimental verification.

Electronic states in the pressure-induced magnetically ordered phase in SmB6

We have carried out the high-pressure measurement of X-ray absorption spectroscopy on the intermediate valence compound SmB6 which shows magnetic ordering as well as an insulator-metal transition at critical pressure Pc ∼ 10 GPa. The valence of Sm atom at room temperature increases with increasing pressure, however it is far below a trivalent state at Pc. In contrast to cases of pressure-induced nonmagnetic-magnetic transition in Yb compounds, which mostly occurs in the scheme of well localized 4f electrons, the present observation suggests that electronic system in SmB6 still possesses strong delocalized characters at Pc.

Structural, electronic, elastic, magnetic and optical properties of the binary intermetallic compounds XAl3 (X=Sc, Dy, Ho, Er, Tm, Yb and Lu)

In this paper, we have studied the structural, electronic, elastic, magnetic and optical properties of the intermetallic XAl3 (X=Sc, Dy, Ho, Er, Tm, Yb and Lu) compounds through density functional theory (DFT). These properties are calculated by using the full potential linearized augmented plane wave (FP-LAPW) method within different approximations of the exchange and correlations (WC-GGA and GGA+U). The calculated structural parameters of the compounds are in excellent agreement with the experimental data. The band structures reveal the metallic behavior of these compounds. The suborbitals d and f of the transition/lanthanide elements have a major contribution to the density of states. The elastic parameters show a high value for the bulk modulus, which results in the ductility, solidity and hardness of these materials. The high value of the shear modulus G and Young's modulus E shows the resistance to plastic deformation and greater stiffness. In order to study the magnetic properties at zero temperature the GGA+U was used. The optical properties were studied in the range of 0 to 10eV, including the dielectric function, absorption coefficient optical conductivity and optical reflectivity.

Synthesis, characterization and antibacterial studies of Tm(III), Yb(III) and Lu(III) complexes of morin

New solid amorphous compounds of Tm(III), Yb(III) and Lu(III) with morin have been synthesized. Their composition and some physicochemical properties have been studied by elemental analysis, thermogravimetric analysis, IR spectroscopy as well as by conductivity, UV/Vis, MS, and NMR spectroscopies in solution. The spectroscopic studies have indicated that the 3-OH hydroxyl group and the carbonyl oxygen of morin were involved in the coordination of metal ion. The antibacterial activity of the synthesized compounds has been determined by the cylinder-plate diffusion and dilution methods (determination of minimum inhibitory concentration).

Synthesis, luminescent and magnetic properties of new tetranuclear lanthanide complexes with 4-hydroxy-2,1,3-benzothiadiazolate and dibenzoylmethanide ligands

Four new tetranuclear complexes, [Ln4(dbm)4(O-btd)6(OH)2] 1a (Ln=Yb), 1b (Ln=Dy) and [Ln4(dbm)6(O-btd)4(OH)2] 2a (Ln=Yb), 2b (Ln=Dy) (O-btd=4-hydroxo-2,1,3-benzothiadiazolate and dbm=dibenzoylmethanide), and their solvates with toluene and tetrahydrofuran were synthesized. The magnetic properties of the complexes 1a, 1b, 2a and 2b have been studied, revealing different magnetic susceptibility patterns for the Yb(III) and Dy(III) complexes in the temperature range 80–300K. Upon lowering the temperature, a weak antiferromagnetic ordering is observed for both Yb compounds, while the Dy derivatives are assumed to show weak ferromagnetic interactions. The Yb complexes 1a and 2a demonstrate strong NIR luminescence at ∼1000nm in CH2Cl2 solution upon excitation of the (O-btd)− ligand. This observation suggests the (O-btd)− ligand to be an efficient antenna ligand for lanthanide-based NIR luminescence.

Evaluating the electronic structure of formal LnII ions in LnII(C5H4SiMe3)31- using XANES spectroscopy and DFT calculations.

The isolation of [K(2.2.2-cryptand)][Ln(C5H4SiMe3)3], formally containing LnII, for all lanthanides (excluding Pm) was surprising given that +2 oxidation states are typically regarded as inaccessible for most 4f-elements. Herein, X-ray absorption near-edge spectroscopy (XANES), ground-state density functional theory (DFT), and transition dipole moment calculations are used to investigate the possibility that Ln(C5H4SiMe3)31- (Ln = Pr, Nd, Sm, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb and Lu) compounds represented molecular LnII complexes. Results from the ground-state DFT calculations were supported by additional calculations that utilized complete-active-space multi-configuration approach with second-order perturbation theoretical correction (CASPT2). Through comparisons with standards, Ln(C5H4SiMe3)31- (Ln = Sm, Tm, Yb, Lu, Y) are determined to contain 4f6 5d0 (SmII), 4f13 5d0 (TmII), 4f14 5d0 (YbII), 4f14 5d1 (LuII), and 4d1 (YII) electronic configurations. Additionally, our results suggest that Ln(C5H4SiMe3)31- (Ln = Pr, Nd, Gd, Tb, Dy, Ho, and Er) also contain LnII ions, but with 4f n 5d1 configurations (not 4f n+1 5d0). In these 4f n 5d1 complexes, the C3h-symmetric ligand environment provides a highly shielded 5d-orbital of a' symmetry that made the 4f n 5d1 electronic configurations lower in energy than the more typical 4f n+1 5d0 configuration.

Crystal structures of ternary compounds Yb(Ga,Si)2-x

Crystal structures of ternary compounds Yb(Ga,Si)2-x

GGA and GGA + U Study of Rare Earth-Based Perovskites in Cubic Phase

The structural, elastic, electronic, and magnetic properties of cubic perovskite RAlO3 (R = Sm, Eu, Gd, Dy, Tb, Ho, Tm, Er, Yb) compounds have been calculated using a full-potential linearized augmented plane wave (FP-LAPW) method within the density functional theory. The exchange-correlation potential was treated with the generalized gradient approximation of Wu and Cohen (WC-GGA) to calculate the total energy. Moreover, the GGA + U−based potential was also applied for the electronic and magnetic properties. The calculated structural properties such as lattice parameter are consistent with the accessible data. The spin-polarized electronic band structure and the calculation of density of state show that DyAlO3, EuAlO3, SmAlo3, TmAlO3, HoAlO3, YbAlO3, and TbAlO3 compounds have a half-metallic nature, and only GdAlO3 and ErAlO3 have a semiconductor nature. The spin-polarized magnetic moment of these compounds reveals that they show a ferromagnetic nature.

Bose glass behavior in(Yb1−xLux)4As3representing randomly diluted quantum spin-12chains

The site-diluted compound (Yb$_{1-x}$Lu$_x$)$_4$As$_3$ is a scarce realization of the linear Heisenberg antiferromagnet partitioned into finite-size segments and is an ideal model compound for studying field-dependent effects of quenched disorder in the one-dimensional antiferromagnets. It differentiates from the systems studied so far in two aspects - the type of randomness and the nature of the energy gap in the pure sample. We have measured the specific heat of single-crystal (Yb$_{1-x}$Lu$_x$)$_4$As$_3$ in magnetic fields up to 19.5 T. The contribution $C_{\perp}$ arising from the magnetic subsystem in an applied magnetic field perpendicular to the chains is determined. Compared to pure Yb$_4$As$_3$, for which $C_{\perp}$ indicates a gap opening, for diluted systems a non-exponential decay is found at low temperatures which is consistent with the thermodynamic scaling of the specific heat established for a Bose-glass phase.

Preparation and luminescent properties of (Tb3+-Yb3+)SSA/(SBA-15) composite materials

In this study, the sulfosalicylic acid (SSA)-Tb and Yb compound were systematically assembled into the pores of SBA-15 by hydrothermal method. The luminescence properties of the prepared materials were studied through luminescence spectra. The influences of the content of Yb3+ and Tb3+ on luminescent properties have been studied, and the luminescence mechanisms were analyzed. By the emission spectrum intensity, the optimum proportion of Tb and Yb was confirmed. In prepared materials, the ordered mesoporous structures were retained, and the prepared materials showed the much stronger emission of Tb3+ at 543nm. The luminescence intensity attained the maximum when Yb3+ molar content was 4%, and the Tb3+ molar content was 2%. The prepared materials have potential applications value in luminescent materials field.

Structure and efficient luminescence upconversion of Ln(iii) aromatic N-oxide coordination polymers.

A series of lanthanide-based coordination polymers {[Yb1-xErx(4,4'-bpdo)3(H2O)2](CF3SO3)3}∞ were synthesised by solvent diffusion techniques, where 4,4'-bpdo = 4,4'-bipyridine-N,N'-dioxide, and using differing mole fractions of Yb(iii) and Er(iii) which were systematically varied (x = 0, 0.05, 0.20, 0.50 and 1). All of the materials obtained were characterised using elemental analyses, single-crystal X-ray diffraction (SXRD) and solid-state photoluminescence studies. Structurally, the coordination polymers crystallise as an isomorphous series of infinite 2D sheets, which contain two inner sphere water molecules, and are isostructural with a previously characterised homometallic Yb(iii) compound. In addition to the normal Near Infra-Red (NIR) luminescence, these compounds also demonstrate upconversion emission upon 980 nm excitation. Upconversion luminescence measurements reveal visible emission in the red, green, and blue regions corresponding to the (2)H11/2→(4)I15/2, (4)F9/2→(4)I15/2 and (2)H9/2→(4)I15/2 transitions of the Er(iii) cation upon two and three-photon excitation. We also observed weak emission from the Er(iii) cation in the UV region for the first time in a Ln-MOF based material.

Electronic structure calculation of the KYb molecule with dipole moments, polarizabilities, and ro-vibrational studies

Ab initio calculations are used to provide the spectroscopic constants (Te, De, ωe, Be, and Re) of the low-lying electronic states for the Potassium–Ytterbium (KYb) compound. The potential energy curves (PECs) have been obtained using the multi-configuration self-consistent field multi-reference configuration interaction (MCSCF/MRCI) calculations. Using the data of the computed PECs and by using the canonical functions approach, the ro-vibrational constants (Ev, Bv, Dv, Rmin, and Rmax) have been calculated for the electronic states up to the vibrational level v=86. The permanent and transition dipole moments along with the components of the electric dipole polarizability (α) have been also calculated. The KYb molecule is experimentally unknown, which provides the focus of the work introduced here by presenting the electronic structure of this new diatomic species. Differences of the previous studied molecules (Alkali–Yb compounds) by our research group are compared with the electronic structure of the current calculated compound. Twenty new molecular electronic states are reported here for the first time.

Hydrothermal controls on the genesis of REE deposits: Insights from an in situ XAS study of Yb solubility and speciation in high temperature fluids (T < 400 °C)

High pressure-high temperature experiments are used to investigate the effect of temperature, pH and fluid composition on the transport and deposition of REE and provide constraints on the role of hydrothermal fluids in the formation of rare metal deposits. In situ X-ray absorption (XAS) measurements were conducted at 50MPa to determine simultaneously the solubility of Yb compounds (Yb2O3, Yb2Si2O7 and YbPO4) and Yb speciation from 200 to 350–400°C in fluids involving Cl, F and P ligands. Yb concentrations were monitored down to tens of ppm from the height of the absorption edge while XANES and EXAFS analyses were used to refine the aqueous speciation of Yb in the high temperature fluids. The XAS analysis suggests that Yb solubility is retrograde from 200°C and that 10 to 100ppm Yb can be dissolved in acidic fluids (pH<2) at T<400°C, most probably as Yb[(H2O)7,8]3+ species. Increasing pH and adding phosphorus trigger the precipitation of Yb compounds from 200 to 400°C. Hence buffering of acid orthomagmatic fluids and leaching of P from host rocks could be major mechanisms in the development of (H)REE enrichments in magmatic-hydrothermal systems.

A family of lanthanide-based coordination polymers with boronic Acid as ligand.

Reactions in water between the sodium salt of 4-carboxyphenylboronic acid (Hcpb) and lanthanide ions (Pr-Nd, Sm-Lu, and Y) led to a family of lanthanide-based coordination polymers with general chemical formula {[Ln(cpbOH)(H2O)2](cpb)}∞. Structural characterizations were ensured by single-crystal X-ray diffraction and solid-state NMR spectroscopy ((11)B, (13)C, and (89)Y). This family of compounds constitutes the first example of lanthanide-based coordination polymers involving 4-carboxyphenylboronic acid as ligand. To evaluate their potential usefulness, luminescent and magnetic properties of some of the compounds that constitute this family were explored. From a magnetic point of view, the Yb(III) compound is the more promising. On the other hand, upon UV irradiation (λexc = 303 nm) ligand phosphorescence is quite intense and offers a sizable blue component to emission spectra. This is quite unusual and can constitute an asset as far as white emission is targeted. Moreover, luminescence properties of these compounds are highly temperature-dependent, and some of them seem promising as molecular thermometers.

Luminescence and Single-Molecule Magnet Behavior in Lanthanide Complexes Involving a Tetrathiafulvalene-Fused Dipyridophenazine Ligand

The reaction between the TTF-fused dipyrido[3,2-a:2',3'-c]phenazine (dppz) ligand (L) and 1 equiv of Ln(hfac)3·2H2O (hfac(-) = 1,1,1,5,5,5-hexafluoroacetyacetonate) or 1 equiv of Ln(tta)3·2H2O (tta(-) = 2-thenoyltrifluoroacetonate) (Ln(III) = Dy(III) or Yb(III)) metallic precursors leads to four mononuclear complexes of formula [Ln(hfac)3(L)]·C6H14 (Ln(III) = Dy(III) (1), Yb(III) (2)) and [Ln(tta)3(L)]·C6H14 (Ln(III) = Dy(III) (3), Yb(III) (4)), respectively. Their X-ray structures reveal that the Ln(III) ion is coordinated to the bischelating nitrogenated coordination site and adopts a D4d coordination environment. The dynamic magnetic measurements show a slow relaxation of the Dy(III) magnetization for 1 and 3 with parameters highlighting a slower relaxation for 3 than for 1 (τ0 = 4.14(±1.36) × 10(-6) and 1.32(±0.07) × 10(-6) s with Δ = 39(±3) and 63.7(±0.7) K). This behavior as well as the orientation of the associated magnetic anisotropy axes have been rationalized on the basis of both crystal field splitting parameters and ab initio SA-CASSCF/RASSI-SO calculations. Irradiation of the lowest-energy HOMO → LUMO ILCT absorption band induces a (2)F5/2 → (2)F7/2 Yb-centered emission for 2 and 4. For these Yb(III) compounds, Stevens operators method has been used to fit the thermal variation of the magnetic susceptibilities, and the resulting MJ splittings have been correlated with the emission lines.

Final-State Interaction in the L3 X-ray Absorption Spectra of Mixed-Valence Ce and Yb Compounds

X-ray absorption spectroscopy (XAS) at the L3 edge of mixed-valence Ce and Yb compounds is a powerful tool for measuring the valence of Ce and Yb ions, but in order to obtain the valence in the ground state it is necessary to analyze the effect of the final-state interaction on XAS profiles, which gives rise to some correction for the XAS-derived valence. We theoretically compare the difference in the final-state interaction for Ce and Yb compounds whose ground states are in the electron–hole symmetry. It is found that the correction for the valence by the final-state interaction is much larger for Ce than for Yb, even if the valences in the ground state are the same. In order to discuss the mechanism of this observation, we define two different final-state interactions: (i) the final-state hybridization between the 4f0 and 4f1 configurations and (ii) that between the 4f1 and 4f2 configurations. Among (i) and (ii) of Ce and Yb compounds, (ii) of Ce compounds is much larger than other interactions, because...

Large Cyclotron Effective Mass Detected by de Haas–van Alphen Effect in YbCu2Si2

De Haas–van Alphen experiments were performed on the valence fluctuation compound YbCu2Si2. For the field direction close to the c-axis in the tetragonal structure, a very large cyclotron effective mass of 43 m0 was detected on branch β, which corresponds to the nearly cylindrical Fermi surface. This mass is one of the largest cyclotron masses detected experimentally in Yb compounds.

Probing Strongly Correlated 4f-Orbital Symmetry of the Ground State in Yb Compounds by Linear Dichroism in Core-Level Photoemission

We show that the strongly correlated 4f-orbital symmetry of the ground state is revealed by linear dichroism in core-level photoemission spectra as we have discovered for YbRh2Si2 and YbCu2Si2. Theoretical analysis tells us that the linear dichroism reflects the anisotropic charge distributions resulting from crystalline electric field. We have successfully determined the ground-state 4f symmetry for both compounds from the polarization-dependent angle-resolved core-level spectra at a low temperature well below the first excitation energy. The excited-state symmetry is also probed by temperature dependence of the linear dichroism where the high measuring temperatures are of the order of the crystal-field-splitting energies.