Yb Compounds Research Articles

Lanthanide Anionic Metal–Organic Frameworks Containing Semirigid Tetracarboxylate Ligands: Structure, Photoluminescence, and Magnetism

A series of lanthanide anionic metal–organic frameworks, [NH2(CH3)2][Ln(MDIP)(H2O)] (Ln = Pr (1), Nd (2), Sm (3), Eu (4), Gd (5), Tb (6), Dy (7); H4MDIP = methylenediisophthalic acid) and [NH2(CH3)2][Ln(MDIP)(H2O)]·0.5NH(CH3)2 (Ln = Er (8), Tm (9), Yb (10)), have been synthesized and characterized. In compounds 1–7, the adjacent Ln3+ ions are intraconnected to form infinite metal-carboxylate oxygen chain-shaped building blocks along the [001] direction. In compounds 8–10, MDIP ligands bridge dinuclear lanthanide centers to form three-dimensional frameworks which can be rationalized as a (4,8)-connected topological net with the Schläfli symbol of (410.614.84)(45.6)2. Dimethylamine cations occupy the vacancy of all the compounds as counterions. The photophysical properties of trivalent Pr, Nd, Sm, Eu, Tb, Dy, Er, Yb compounds at room temperature were investigated and showed that MDIP is an efficient sensitizer of the luminescence of both the Tb3+ ion emitting visible light and the Yb3+ ion emitting in the near-IR. Antiferromagnetic interactions between Gd3+ ions were observed from magnetic susceptibility data.

Optical and Structural Properties of Yb-Doped ZnO Thin Waveguide Films with Er<sup>+</sup> Ions Implantation

Yb-doped ZnO optical waveguide thin films were deposited on sapphire substrates by radiofrequency (RF) magnetron sputtering technology, and then Er+ions with the energy of 200 KeV were implanted into the as-deposited films, the implantation dose was 1×1015ions/cm2. Optical waveguide properties and film thicknesses were studied by prism coupling method. Film thicknesses, element components and Er+ions range distrbution were studied by Rutherford backscattering (RBS) technique. The basic structure and phase of the films were studied using X-ray diffraction (XRD). The properties of optical frequency upconwersion were investigated by fluorescence spectrometer. The results demonstrated that the Yb-doped ZnO films with Er-implantation have planar waveguide structure and the waveguide properties were changed compared with the virgin ZnO films. The effective refractive indices of the films decreasing with the amount of Yb-doped concentration increasing. Yb concentration in films associated with targets but more than that in them. The films shown the classic structure of c-axis preferred orientation. The compounds of Yb:Zn and Er:Zn were appeared in the films. Inspired the films by 980 nm laser in room temperature, stimulated optical emission between 300~720 nm was not observed.

Photon Energy Dependent Hard X-ray Photoemission Spectroscopy of YbCu2Si2

We have performed photon energy ( h ν) dependent hard X-ray photoemission spectroscopy (HAXPES) for YbCu 2 Si 2 , which is a heavy Fermion compound with intermediate Yb valence. We identified that the bulk components in the Si 1 s and Yb 3 d spectra develop with increasing h ν from 2.5 to 6 keV. Moreover, the temperature dependence of the Yb 3 d spectra measured at h ν= 8 keV has shown a valence fluctuation behavior. These results suggest that high h ν HAXPES is essential to determine the mean valence of the Yb compounds.

Intermediate valence in Yb compounds probed by 4fphotoemission and resonant inelastic x-ray scattering

Experimental data from $4f$ photoemission and resonant inelastic x-ray scattering experiments on the intermediate valent compound YbRh${}_{2}$Si${}_{2}$ have been compared with results of theoretical simulations. It was found that the high-energy excitations inherent to these techniques affect the spectral intensities related to different $4f$ configurations differently. Although the final states in $4f$ photoemission and x-ray absorption or resonant inelastic x-ray scattering are rather unalike, a comparable influence was found for both cases. Higher occupied $4f$ shells seem to be energetically favored in the excited states and appear overemphasized in the spectrum as compared to the ground state. For a quantitative Yb valence determination from x-ray spectroscopies, diagrams are suggested that seem to be applicable also for other intermediate valent Yb compounds.

Nuclear chemical transformations of ytterbium and lutetium radionuclides following (n,γ) and beta decay reactions in Tris(2,2,6,6-tetramethyle-3,5-heptanedionato)Yb(III)

The behavior of recoiled radionuclides (169)Yb, (175)Yb, and (177)Lu resulting from the reactions (168)Yb(n,γ)(169)Yb, (174)Yb(n,γ)(175)Yb, and (176)Yb(n,γ)(177)Yb → (177)Lu, respectively, in the organometallic Tris(2,2,6,6-tetramethyle-3,5-heptanedionato)Yb(III) compound was investigated. Paper chromatography as well as thin layer chromatography, using different patterns of solvents and developers, are discussed. It was found that the organic and inorganic species were of different types and the species resulting from (n,γ) differed from those resulting from β-decay. The species resulting from β-decay reaction were little affected by the type of paper chromatography, while those resulting from (n,γ) reaction were not affected at all. The retention depended on the type of paper and the pattern of solvent/developer. Paper chromatography gave the best results when the compound was dissolved and developed in toluene. The retention values of (177)Lu in three different cases were determined. The obtained retention values indicated that the compound under investigation was not suitable for the purpose of high specific activity radioisotope production.

Hydrothermal synthesis, thermal and luminescent investigations of lanthanide(III) coordination polymers based on the 4,4′-oxybis(benzoate) ligand

In this study, new series of lanthanide 4,4′-oxybis(benzoates) of the general formula Ln2oba3·nH2O, where Ln = lanthanides from La(III) to Lu(III), oba = C12H8O(COO) 2 2− and n = 3–6, has been prepared under hydrothermal conditions. The compounds were characterized by elemental analysis, infrared spectroscopy, X-ray diffraction patterns measurements and different methods of thermal analysis (TG, DSC, and TG-FTIR). In addition, photoluminescence properties of the selected complexes have been investigated. Crystalline compounds are isostructural in the whole series. Both carboxylate groups are deprotonated and engaged in the coordination of Ln(III) ions. Heating of the complexes leads to the dehydration and next decomposition processes. Although of the same structure, the removal of water molecules proceeds in different ways. In the nitrogen atmosphere, they decompose releasing water, carbon oxides and phenol molecules. The complexes of Eu(III), Tb(III) and Dy(III) exhibit photoluminescence in the visible range, whereas the compounds of Nd(III) and Yb(III) in the near-infrared region upon excitation by UV light.

Ferromagnetism in YbCu2Si2at high pressure

We demonstrate from detailed ac-susceptibility and calorimetry studies under hydrostatic pressure that YbCu2Si2 probably orders ferromagnetically at high pressure. The (p,H,T) phase diagram, shows that the transition temperature increases with pressure, but also with an applied magnetic field. We suggest that many ytterbium systems may show a trend towards ferromagnetism and we discuss the possible reasons for this. We also examine the implications, including the potential of YbCu2Si2 and other Yb compounds for further studies of the rich physical properties that may occur near a ferromagnetic critical point.

Neutron powder diffraction study of the ternary RMgSn (R=Ce–Nd, Tb–Tm, Yb) compounds

The ternary intermetallic RMgSn compounds are studied by neutron powder diffraction. The CeScSi-type PrMgSn and NdMgSn compounds present a commensurate antiferromagnetic structure, while the (Tb–Tm)MgSn are characterized by an incommensurate sine-wave modulated magnetic structure, which can tend to a square-modulated arrangement at low temperature due to appearance of higher odd integer harmonics. The TiNiSi-type CeMgSn compound is also characterized by an incommensurate sine-wave modulated magnetic structure, while PrMgSn exhibits a ferromagnetic arrangement with a canting at low temperature. Finally, the ZrNiAl-type YbMgSn compound evidences no magnetic ordering. These results are discussed and compared with those published for the other CeScSi-type compounds.

ChemInform Abstract: Formation and Physical Properties of a Novel Compound Yb3Pt23Si11.

AbstractThe title compound is prepared by arc melting of the elements and characterized by powder XRD and magnetic, electrical resistivity, and heat capacity measurements.

22pGC-15 Yb系シャストリー・サザーランド格子化合物の秩序状態(22pGC 価数揺動,少数キャリア等,領域8(強相関系:高温超伝導,強相関f電子系など))

22pGC-15 Yb系シャストリー・サザーランド格子化合物の秩序状態(22pGC 価数揺動,少数キャリア等,領域8(強相関系:高温超伝導,強相関f電子系など))

Structural and physical properties of the new intermetallic compound Yb 3Pd 2Sn 2

The crystal structure of the ternary intermetallic compound Yb 3Pd 2Sn 2 has been determined ab initio from powder X-ray diffraction data. The compound crystallizes as a new structure type in the orthorhombic space group Pbcm and lattice constants a=0.58262(3), b=1.68393(8), c=1.38735(7) nm. Yb 3Pd 2Sn 2 is composed of a complex ∞[Pd 2Sn 2] δ− polyanionic network in which the Yb ions are embedded. A comparison between this structure and those of Eu 3Pd 2Sn 2 and Ca 3Pd 2Sn 2, other novel polar intermetallic compounds, was made. DC susceptibility and 170Yb Mössbauer spectroscopic measurements indicate a close-to divalent Yb behavior. Moreover, a hybridization between 4 f and conduction electrons is suggested by electronic structure calculations and heat capacity measurements.

Formation and physical properties of a novel compound Yb 3Pt 23Si 11

The crystal structure of the novel compound Yb 3Pt 23Si 11 has been determined from powder X-ray diffraction data to be isotypic with cubic Ce 3Pt 23Si 11 (space group F m 3 ¯ m ; a = 1.68052(5) nm). Magnetic susceptibility, electrical resistivity and heat capacity measurements, performed down to 0.4 K, revealed that Yb 3Pt 23Si 11 is a moderately enhanced paramagnetic compound with fairly unstable 4 f electronic shell.

Reentrant quantum criticality in Yb2Pd2Sn

We report the discovery of two consecutive, pressure driven magnetic instabilities in ${\mathrm{Yb}}_{2}{\mathrm{Pd}}_{2}\mathrm{Sn}$. They emerge in a non-Fermi liquid environment at the initial and the final point of a dome-like, single magnetic phase at pressures ${\mathrm{p}}_{\mathrm{c}1}\ensuremath{\approx}1$ GPa and ${\mathrm{p}}_{\mathrm{c}2}\ensuremath{\approx}4$ GPa. This singular behavior of Yb compounds is supposed to result from mutually competing, pressure modified energy scales, which in case of ${\mathrm{Yb}}_{2}{\mathrm{Pd}}_{2}\mathrm{Sn}$ cause a sign change of the pressure dependence of the Kondo temperature ${T}_{K}$ and magnetic ordering temperature ${T}_{N}$.

Theory of low energy excitations in resonant inelastic x-ray scattering for rare-earth systems: Yb compounds as typical examples

Theoretical predictions are given for low energy excitations, such as crystal field excitations and Kondo resonance excitations, to be detected by high-resolution measurements of resonant inelastic x-ray scattering (RIXS) of rare-earth materials with Yb compounds as typical examples. Crystal field excitations in the Yb $3d$ RIXS of a Yb${}^{3+}$ ion in the cubic crystal field are formulated, and the calculation of RIXS spectra for YbN is done. Kondo resonance excitations revealed in the Yb $3d$ RIXS spectra are calculated for mixed-valence Yb compounds, Yb${}_{1\ensuremath{-}x}$Lu${}_{x}$Al${}_{3}$, in the leading term approximation of the 1/${N}_{f}$ expansion method with a single impurity Anderson model. It is emphasized that the high-resolution RIXS with polarization dependence is a powerful tool to study the crystal field levels together with their symmetry and also the Kondo bound state in rare-earth compounds. Some in-depth discussions are given on the polarization effects of RIXS, including $4d$ and $2p$ RIXS spectra, the coherence effect of the Kondo bound states, and the importance of the high-resolution RIXS spectra for condensed matter physics under extreme conditions.

Synthesis and Properties of BaZr0.1Ce0.7Y02-xMxO3-δ (x = 0, 0.1; M = Dy, Yb) Compounds

The following barium cerate zirconate compounds were prepared by the solid state route: BaZr0.1Ce0.7Y0.2O3-δ, BaZr0.1Ce0.7Dy0.2O3-δ, BaZr0.1Ce0.7Y0.1Dy0.1O3-δ, The powders were attrition milled, pressed and sintered at 1550 °/4 h. X-ray diffraction data of all compositions show the perovskite orthorhombic phase (powders) and the perovskite cubic phase (pellets). Impedance spectroscopy measurements in the 5 Hz-13 MHz frequency range show that Dy may substitute total or partially for Y without noticeable change in the electrical conductivity, whereas the Yb substitution leads to a decrease in the electrical conductivity. The bulk electrical resistivity follows the trend: Yb- < Dy- < Dy-Y- < Yb-Y- < Y-doped barium cerate zirconate sintered ceramics. A detailed scanning probe microscopy analysis of the polished and thermally etched surfaces of the sintered pellets show images of sub-intergranular regions, which are further evidences of the large grain boundary electrical resistivity of barium cerate compounds.

Crystal field effect on X-ray magnetic circular dichroism spectra at the L2,3 absorption edges of mixed-valence Ce and Yb compounds in high magnetic fields

A theoretical study is presented, with an extended single impurity Anderson model, for the crystal field effect on the X-ray magnetic circular dichroism (XMCD) spectra at L2,3 edges of mixed-valence Ce and Yb compounds in high magnetic fields. The crystal field acting on the 4f electrons is assumed to have cubic symmetry. Due to the competition among the effects of crystal field, mixed valency, and external magnetic field, the magnetic-field-dependence of XMCD spectra exhibits a variety of features; for instance, the branching ratio, R(L2/L3), of L2 and L3 XMCD intensities of Ce compounds can take R(L2/L3) > 1.0 and 0 and <0. It is shown that the magnetic-field-dependence of the total XMCD intensity I(L2 + L3) is proportional to the magnetization curve, but that of R(L2/L3) gives more precise information on the ground state wavefunction in magnetic fields. A new and useful method to correlate the XMCD spectra, the 4f magnetization and the ground state wavefunction is proposed and used to discuss the relation between I(L2 + L3) and the magnetization curve and that between R(L2/L3) and the ground state wavefunction.

High pressure effect on structural and mechanical properties of some LnO (Ln=Sm, Eu, Yb) compounds

The structural and mechanical properties of LnO (Ln=Sm, Eu, Yb) compounds have been investigated using a modified interionic potential theory, which includes the effect of Coulomb screening. We predicted a structural phase transition from NaCl (B 1)- to CsCl (B 2)-type structure and elastic properties in LnO compounds at very high pressure. The anomalous properties of these compounds have been correlated in terms of the hybridisation of f-electrons of the rare earth ion with conduction band and strong mixing of f-states of lanthanides with the p-orbital of neighbouring chalcogen ion. For EuO, the calculated transition pressure, bulk modulus and lattice parameter are close to the experimental data. The nature of bonds between the ions is predicted by simulating the ion–ion (Ln–Ln and Ln–O) distances at high pressure. The second order elastic constants along with shear modulus and Young's modulus, elastic anisotropy and Poisson's ratio are also presented for these oxides.

Antimony-Based Compounds with the Anti-Th3P4 Structure as Potential High-Temperature Thermoelectric Materials

We present a combined experimental and theoretical study of thermoelectric properties and lattice dynamics of the R4Sb3 (R = La, Yb) compounds with the anti-Th3P4 structure. Bi alloying of Yb4Sb3 was found to improve the thermoelectric properties but not as well as La or Sm alloying. From the band structure, we are able to explain the origin of the relatively large and positive thermopower in Yb4Sb3 and of the small and negative thermopower found in La4Sb3 at high temperatures. Since the contribution of the 4f level of Yb atoms must be negative, as in other intermediate valence Yb-based compounds, the positive thermopower in Yb4Sb3 is due to the conduction electrons. We conjecture that the origin of the low thermal conductivity is similar to that of skutterudites, i.e., due to hybridization between acoustic and low-energy optical modes of the same symmetry.

Phase relations in the CuAsS2-MS (M — Pb, Eu, Yb) systems

The CuAsS2-PbS, CuAsS2-EuS, and CuAsS2-YbS systems have been studied for the first time and their phase diagrams have been mapped out. We have identified the MCuAsS3 (M — Pb, Eu, Yb) compounds (seligmannite structure, Z = 4, sp. gr. Pmn21) and determined their lattice parameters: a = 8.125, b = 8.748, c = 7.644 A (PbCuAsS3); a = 8.04, b = 8.66, c = 7.60 A (EuCuAsS3); a = 8.00, b = 8.62, c = 7.54 A (YbCuAsS3).

Yb3AuGe2In3: An Ordered Variant of the YbAuIn Structure Exhibiting Mixed-Valent Yb Behavior

Yb(3)AuGe(2)In(3) was obtained as large single crystals in high yield from reactions run in liquid indium. Single crystal X-ray diffraction data show that Yb(3)AuGe(2)In(3) is an ordered variant of YbAuIn with lattice constants, a = b = 7.3153(8) Å and c = 4.4210(5) Å, and space group P(6)2m. The parent compound YbAuIn was also studied for comparison. YbAuIn crystallizes in the ZrNiAl structure type, hexagonal, P(6)2m space group with lattice parameters a = b = 7.7127(11) Å and c = 4.0294(8) Å. In Yb(3)AuGe(2)In(3), Ge substitutes for one of the two Au positions in the ternary compound Yb(3)Au(3)In(3). The structure can be described as alternating [Ge(2)In(3)] and [Yb(3)Au] slabs that stack along the c-axis. The magnetic susceptibility data follow a modified Curie-Weiss law. The effective magnetic moment μ(eff) of 0.52 μ(B)/Yb atom was deduced from the Curie constant and Curie-Weiss constant of θ(p) = -1.5 K indicating antiferromagnetic interactions in Yb(3)AuGe(2)In(3). X-ray absorption near edge spectroscopy (XANES) measurements indicate intermediate valency for Yb in both compounds. The metallic nature of both compounds was confirmed by the resistivity measurements. Specific heat data for Yb(3)AuGe(2)In(3) and YbAuIn give an electronic γ term of 31 and 84 mJ/mol·K(2), respectively, suggesting that the ternary analog is a "light" heavy fermion compound.