Ytterbium Content Research Articles

The ion-irradiation tolerance of the pyrochlore to fluorite Ho(x)Yb(2-x)TiO5 and Er2TiO5 compounds: A TEM comparative study using both in-situ and bulk ex-situ irradiation approaches

We refine the crystal structures of a systematic series of compounds with the general composition Ho(x)Yb(2-x)TiO5 (x = 2, 1.6, 1.2, 1, 0.8, 0.4, 0) and Er2TiO5 and find a transition from defect-pyrochlore to defect-fluorite structure with increasing ytterbium content, decreasing lanthanide radius. Short-range structure modulations consisting of pyrochlore-like nano-domains are systematically characterised using transmission electron microscopy. We test the Kr2+ 1 MeV ion-irradiation response of Ho2TiO5, HoYbTiO5, Yb2TiO5, and Er2TiO5, via the crystalline to amorphous transition observed by using the in-situ TEM approach. The critical dose of amorphisation, Dc, was measured at various temperatures and used to calculate the critical temperature for maintaining crystallinity, Tc. A trend of lower Tc values with decreasing lanthanide radius is found. We describe a new approach for determining Tc values using cross-sectional TEM analysis of ex-situ bulk irradiated, 1 MeV Se+, samples; Ho2TiO5, HoYbTiO5 and Yb2TiO5. The results of Dc and Tc values using the two approaches vary; however the trends across the sample system remain the same.

Lanthanides and Actinides in Humic Acids of Soils and Paleosols of Forest-Steppe Conditions in the Southern Urals

This article analyzes the lanthanum, cerium, samarium, europium, terbium, ytterbium, lutetium, uranium, and thorium content in humic acids within soil and paleosol surface horizons from the southern steppe in the Southern Urals. Research demonstrates similar accumulation levels of these elements in paleosols isolated from both the active medium between 3.6 and 3.3 thousand years ago and in recent background soils. Despite the lack of significant differences, research has shown a growing content among the rarest metals in the series “the buried paleosols–man-modified paleosols of settlement–recent background soils”. Research has detected the lowest content of La, Ce, Sm, Eu, Yb, Lu, and Th in preparations of humic acids of recent background soils. This reveals a close content to most elements in humic acids of paleosols buried under barrows and ancient settlement paleosols. Additionally, it indicates the virtual absence of anthropogenic impact on binding lanthanides and actinides by humic acids in ancient times. The contribution of humic acids into the common pool for each element was evaluated using a special approach. Research showed that there was less than half the share of elements associated by humic acids of paleosols than in the recent background chernozems in the total pool of lanthanides and actinides. This article considers the prospects of using humic acids of recent and ancient soils in identifying behavioral patterns of metal complexes through time.

Nanocrystalline lanthanide tetraphosphates: Energy transfer processes in samples co-doped with Pr3+/Yb3+ and Tm3+/Yb3+

Photoluminescent properties of nanocrystalline powders of the LiLa(PO3)4 system co-doped with Pr3+/Yb3+ or Tm3+/Yb3+ ions were reported. The powders were synthesized by precipitation method and annealed at 450 °C. Two series of the samples were prepared with 1 mol% of praseodymium or thulium ions and with various ytterbium content (from 2% up to 16%). Both the up- and downconversion energy transfers were studied, in particular, the spectra and kinetics of photoluminescence under blue (into Pr3+ or Tm3+ ions, respectively) and NIR (into Yb3+ ions) excitations. The possible mechanisms of energy migration were discussed. Higher ytterbium concentration resulted in higher energy transfer efficiencies for both tetraphosphate systems.

Synthesis, Characterization, and Low Temperature Transport Properties of Eu11-xYbxCd6Sb12 Solid-Solution Zintl Phases.

Eu11-xYbxCd6Sb12 Zintl solid solutions have been prepared by tin flux reaction by employing the elements Eu/Yb/Cd/Sb/Sn in the ratio 11 - xp:xp:6:12:30, where xp is an integer less than 11 representing the preparative amount of Eu (11 - xp) and Yb (xp). Efforts to make the Yb compositions for x exceeding ∼3 resulted in structures other than the Sr11Cd6Sb12 structure type. The crystal structures and compositions were determined by single-crystal and powder X-ray diffraction and wavelength-dispersive X-ray analysis measurements. The title solid-solution Zintl compounds crystallize in the centrosymmetric monoclinic space group C2/m (no. 12, Z = 2) as the Sr11Cd6Sb12 structure type (Pearson symbol mC58), and the lattice parameters decrease with increasing ytterbium content. Single crystal X-ray diffraction shows that Yb atoms are not randomly distributed in the Eu sites but have a site preference which can be attributed to size effects. The influence of the rare earth (RE) metal sites on thermal and electronic properties of RE11Cd6Sb12 solid solutions has been studied by measuring their thermoelectric properties from 5 to 300 K after consolidation by either spark plasma sintering (SPS) or hot pressing (HP). Electron microprobe analysis reveals that some of the rare earth metal is lost during SPS; as a result pellets formed through SPS have lower electrical resistivity by an order of magnitude due to increased hole-charge carrier concentrations. While the carrier concentration increases, the mobility decreases due to deficiencies in Eu content. Refinement of powder X-ray diffraction shows that Eu loss is mainly from the Eu1 crystallographic site, which has a unique coordination suggesting that this site plays a key role in the transport properties of RE11Cd6Sb12.

Temperature-dependent absorption and emission of potassium double tungstates with high ytterbium content.

We study the spectroscopic properties of thin films of potassium ytterbium gadolinium double tungstates, KYb0.57Gd0.43(WO4)2, and potassium ytterbium lutetium double tungstates, KYb0.76Lu0.24(WO4)2, specifically at the central absorption line near 981 nm wavelength, which is important for amplifiers and lasers. The absorption cross-section of both thin films is found to be similar to those of bulk potassium rare-earth double tungstates, suggesting that the crystalline layers retain their spectroscopic properties albeit having >50at.% Yb3+ concentration. The influence of sample temperature is investigated and found to substantially affect the measured absorption cross-section. Since amplifiers and lasers typically operate above room temperature due to pump-induced heating, the temperature dependence of the peak-absorption cross-section of the KYb0.57Gd0.43(WO4)2 is evaluated for the sample being heated from 20 °C to 170 °C, resulting in a measured reduction of peak-absorption cross-section at the transitions near 933 nm and 981 nm by ~40% and ~52%, respectively. It is shown that two effects, the change of Stark-level population and linewidth broadening due to intra-manifold relaxation induced by temperature-dependent electron-phonon interaction, contribute to the observed behavior. The effective emission cross-sections versus temperature have been calculated. Luminescence-decay measurements show no significant dependence of the luminescence lifetime on temperature.

Preparation of ytterbium substituted BiFeO3 multiferroics by mechanical activation

Samples in the system Bi1−xYbxFeO3 (0.02≤×≤0.07) have for the first time been prepared by mechanical activation followed by sintering. XRD and DSC measurements show that the solubility limit of ytterbium in the R3c Bi1−xYbxFeO3 system is reached at x∼0.03. Higher ytterbium contents lead to a two-phase mixture of a main R3c phase of approximate composition Bi0.97Yb0.03FeO3 and ytterbium enriched secondary phases that cannot be readily indexed or quantified due to their small amount. DSC and temperature-dependent XRD showed that while the magnetic ordering temperature, TN, was unaffected by Yb substitution, the ferroelectric ordering, TC, declined. Temperature-dependent XRD patterns show that all samples exhibit rhombohedral R3c to orthorrhombic Pnma phase transitions. Diffuse reflectance spectroscopy suggests the potential use of the samples in photocatalytic applications due to their low band gap energy. Impedance spectroscopy and magnetic measurements show that samples are electrically homogenous and highly insulating, exhibiting antiferromagnetic behaviour at room temperature.

The double rare-earth substituted bismuth oxide system Bi3Y1 − xYbxO6

Structure and electrical conductivity in the double rare-earth substituted system Bi3Y1−xYbxO6 (0.00≤x≤1.00) is discussed. Structural characterization, by X-ray and neutron powder diffraction, confirms a full δ-Bi2O3 type solid solution. This structure is maintained up to 850°C, with no visible evidence for phase separation over the timescale of the diffraction experiments. Small compositional changes in oxide ion distribution are observed, with Yb rich compositions favoring a more centralized oxide ion distribution in the tetrahedral cavities. Electrical characterization, by a.c. impedance spectroscopy, reveals the system to be highly conducting, with measurements of transference number indicating this conductivity to be almost purely ionic at temperatures above ca. 600°C. At lower temperatures, transference number decreases with increasing ytterbium content. Maxima in activation energy and conductivity pre-exponential factor at high temperatures are observed at x= 0.50 and are discussed in terms of changes in configurational entropy. This behaviour resembles the “mixed alkali effect” frequently observed in glasses. However, in the present case there is no corresponding minimum in conductivity and the effect is associated with the immobile sublattice.

Thermoelectric properties of Yb-doped La0.1Sr0.9TiO3 ceramics at high temperature

The effect of ytterbium doping on the thermoelectric properties of La0.1Sr0.9TiO3 ceramics has been investigated at the temperature range between 300K and 1000K. Samples with different ytterbium concentrations have been synthesized by the conventional solid state reaction technique. An X-ray diffraction pattern suggests that the dominant crystal structure is of perovskite, with a small amount of pyrochlore phase of Yb2Ti2O7. The electrical resistivities of all samples exhibit a minimum in the temperature range between 300K and 1000K. The minimum values of electrical resistivity are 1.5mΩcm, 2.0mΩcm, 3.9mΩcm, 7.1mΩcm, and 9.0mΩcm for x=0.01, 0.03, 0.05, 0.07, and 0.10, respectively. With the increasing ytterbium content, the electrical resistivity enhanced dramatically, the Seebeck coefficients are increased marginally, and the thermal conductivities are reduced moderately. The lowest thermal conductivity of 3.9W/mK is obtained in sample of La0.1Sr0.89Yb0.01TiO3, which exhibits maximum figure of merit 0.20 at 963K.

Electrochemical study on preparation of Mg-Li-Yb alloys in LiCl-KCl-KF-MgCl2-Yb2O3 melts

This paper presented a novel study on electrochemical codeposition of Mg-Li-Yb alloys in LiCl-KCl-KF-MgCl2-Yb2O3 melts on molybdenum. The factors of the current efficiency were investigated. Electrolysis temperature had great influence on current efficiency; the highest current efficiency was obtained when electrolysis temperature was about 660 °C. The content of Li in Mg-Li-Yb alloys increased with the high current densities. The optimal electrolytic temperature and cathodic current density were around 660 °C and 9.3 A/cm2, respectively. The chemical content, phases, morphology of the alloys and the distribution of the elements were analyzed by X-ray diffraction, scanning electron microscopy, inductively coupled plasma mass spectrometry, respectively. The intermetallic of Mg-Yb was mainly distributed in the grain boundary of the alloys, presented as reticulated structures, and refined the grains. The lithium and ytterbium contents in Mg-Li-Yb alloys could be controlled by changing the concentration of MgCl2 and Yb2O3 and the electrolysis conditions.

Luminescent properties of ytterbium-doped ternary lanthanum chloride

Studies of the absorption and temperature dependence of photoluminescence spectra and luminescence decay times of the intra-shell f– f transitions ( 2 F 5/2 ↔ 2 F 7/2) of Yb 3+ ions in K 2LaCl 5:Yb 3+ powders with 5, 10, 15 and 25% of ytterbium are presented. The spectroscopic properties of the powders with different ytterbium content are compared. Experiments were performed at the temperatures from 25 to 300 K. The strong emission around 982 nm has been observed under direct excitation of the luminescence center with 960 nm line of continuous wave Ti:sapphire laser pumped by Ar-ion laser. The temperature quenching effect of the luminescence was rather week, especially in the samples with higher concentration of ytterbium (15 and 25%). Additionally the probability of the f– f radiative transitions of the Yb 3+ ions in these powders was almost temperature independent for more heavily doped samples (with 15 and 25% of Yb) and only weakly temperature dependent for less doped samples (with 5 and 10% of Yb). These results reveal high thermal stability of the optical properties of the examined powders.

Thermomechanical properties of Yb3+ doped laser crystals: Experiments and modeling

Thermal conductivity values of several laser materials were determined by photothermal measurements and compared to predicted values. The effect of the ytterbium doping concentration could be modeled using a simple cationic mass difference model. For ytterbium content corresponding to an absorption coefficient of 10 cm−1 (or 85% absorption of the pump power) Yb:GdVO4 (c-axis) and Yb:Gd3Ga5O12 laser materials present the highest measured thermal conductivity values of 8.1 W m−1 K−1 and 7.7 W m−1 K−1, respectively. Yb:Y3Al5O12, Yb:Lu3Al5O12, Yb:CaGdAlO4, and Yb:YAlO3 belong to the 6–7 W m−1 K−1 range while Yb:CaF2 and Yb:Lu2SiO5 are situated in the 5–6 W m−1 K−1 range. Other matrices such as Yb:SrLaGa3O7, Yb:CaGdAl3O7, Yb:SrGdGa3O7, and Yb:BaLaGa3O7 have thermal conductivity values lower than 5 W m−1 K−1. With the knowledge of the thermal conductivities and the determination of the thermal expansion coefficients, thermal shock parameters are evaluated for several ytterbium doped laser hosts.

Magnetic Properties of New Diluted Magnetic Semiconductors Pb<sub>1-X-Y</sub>Mg<sub>X</sub>Yb<sub>Y</sub>Te

We have studied the magnetic susceptibility, magnetization and electron paramagnetic resonance (EPR) in the diluted magnetic semiconductor Pb1-x-yMgxYbyTe. The magnetic susceptibility of this system is a superposition of the matrix diamagnetism, the paramagnetic contribution of electrons localized in the ytterbium band, and the Curie-Weiss paramagnetism provided by Yb3+ ions. The concentration of Yb3+ ions monotonically increases with the ytterbium content, while a significant fraction of ytterbium ions remains in a nonmagnetic Yb2+ state. A pronounced hyperfine structure was revealed in the EPR spectra. It was ascribed to the interaction between the electron magnetic moment of an unfilled electron shell of Yb3+ ions and nuclear magnetic moment of the 173Yb isotope. The estimated values of the effective g-factor (g1.997 0.002) and the hyperfine-interaction constant (173A=0,56 cm-1) were found to be almost independent of both alloy composition and temperature.

Electrical conductivity and thermal expansion of neodymium–ytterbium zirconate ceramics

(Nd 1− x Yb x ) 2Zr 2O 7 (0 ≤ x ≤ 1) ceramics were prepared by pressureless-sintering to obtain dense bulk materials. The electrical conductivity of (Nd 1− x Yb x ) 2Zr 2O 7 was investigated by complex impedance spectroscopy over a frequency range of 20 Hz to 2 MHz from 723 to 1173 K in air. A high-temperature dilatometer was used to analyze thermal expansion coefficient of (Nd 1− x Yb x ) 2Zr 2O 7 in the temperature range of 373–1523 K. The measured electrical conductivity obeys the Arrhenius relation. The grain conductivity of each composition in (Nd 1− x Yb x ) 2Zr 2O 7 gradually increases with increasing temperature. A decrease of about one order of magnitude in grain conductivity is found at all temperature levels when the Yb content increases from x = 0.3 to x = 0.5. The highest electrical conductivity value obtained in this work is 9.32 × 10 −3 S cm −1 at 1173 K for (Nd 0.7Yb 0.3) 2Zr 2O 7 ceramic. (Nd 1− x Yb x ) 2Zr 2O 7 ceramics are oxide-ion conductors in the oxygen partial pressure range from 1.0 × 10 −4 to 1.0 atm at all test temperature levels. Thermal expansion coefficients of (Nd 1− x Yb x ) 2Zr 2O 7 gradually decrease with increasing ytterbium content at identical temperature levels.

Electrical conductivity of defect fluorite-type (Gd1−xYbx)2Zr2O7 solid solutions

Abstract (Gd 1− x Yb x ) 2 Zr 2 O 7 (0 ≤ x ≤ 1) solid solutions were prepared by pressureless-sintering process at 1973 K to investigate the substitution effect of Yb for Gd on their electrical properties. Electrical conductivity of (Gd 1− x Yb x ) 2 Zr 2 O 7 solid solutions were measured using complex impedance spectroscopy from 673 to 1173 K over a frequency range of 2 Hz to 2 MHz in air. (Gd 1− x Yb x ) 2 Zr 2 O 7 are oxide-ion conductor in the oxygen partial pressure range from 1.0 × 10 −4 to 1.0 atm at all test temperature levels. The measured values of grain conductivity obey the Arrhenius relation. The grain conductivity of (Gd 1− x Yb x ) 2 Zr 2 O 7 increases with increasing temperature. However, the grain conductivity of (Gd 1− x Yb x ) 2 Zr 2 O 7 gradually decreases with increasing ytterbium content at identical temperature levels.

Thermal properties and cw-laser operation of the ytterbium doped borate Li 6Y(BO 3) 3

Single crystals of Yb doped Li 6Y(BO 3) 3 were obtained by Czochralski method. The first laser tests were encouraging. Different parameters have been investigated to improve cw-laser performances. Thermal properties but also ytterbium content, crystal thickness and pump polarisation are reported. The best crystal configuration was determined and led to high power cw-laser tests equal to 2 W output power.

Preparation of Yb-Doped Sc2O3 Transparent Ceramics for Laser Applications

AbstractPolycrystalline transparent Yb:Sc2O3 ceramics were obtained in the best conditions by a solid-state reaction route using high purity Sc2O3 and Yb2O3 powders with TEOS as a sintering aid. The as-prepared powders containing various ytterbium content were characterized by BET measurements, XRD and FEG-SEM. The sintering behaviour of the powders was investigated by dilatometry. The sintered materials microstructures were observed by FEG-SEM. EPMA allowed to characterize the repartition of the dopant Yb3+ in the Sc2O3 matrix.

Ln 3+:KLu(WO 4) 2/KLu(WO 4) 2 epitaxial layers: Crystal growth and physical characterisation

Monoclinic epitaxial layers of single doped KLu 1− x Ln x (WO 4) 2 (Ln 3+ = Yb 3+ and Tm 3+) have been grown on optically passive KLuW substrates by liquid phase epitaxy (LPE) technique using K 2W 2O 7 as solvent. The ytterbium content in the layer is in the range of 0.05 < x < 0.75 atomic substitution and the studied thulium concentrations are 0.05 < x < 0.10. The grown epitaxies are free of macroscopic defects and only in highly ytterbium-doped epilayers do some cracks or inclusions appear. The refractive indices of the epilayers were determined. The absorption and emission cross sections of ytterbium and thulium in KLuW are characterised and laser generation results are presented and discussed.

Photoluminescence Study of In-Situ Rare Earth Doped PVT-Grown SiC Single Crystals

Several SiC bulk crystals were grown with erbium and ytterbium as doping materials. Erbium contents determined by secondary ion mass spectroscopy (SIMS) ranged from 1.2 · 1014 cm-3 to 1.04 · 1015 cm-3, while ytterbium contents were below SIMS detection limit. Photoluminescence (PL) investigations of the characteristic 4f-4f-transition lines revealed a reduced luminescence yield in highly nitrogen and aluminum co-doped samples. Also, samples without intentional co-doping grown on the C-face showed less luminescence intensity than those grown on the Si-face. A stabilizing effect of erbium doping on the 4H polytype was observed.

Deep defect states in diluted magnetic semiconductors Pb1-xSnxTe:Yb

The galvanomagnetic effects in new diluted magnetic semiconductors Pb $_{1-x}$ Sn x Te:Yb were studied to build the energy level diagram under variation of the alloy composition and establish the connection between the parameters of electronic structure and magnetic properties. It was found that the Hall coefficient increases almost by order of magnitude with increasing the temperature. As tin content decreases, while the ytterbium concentration grows, the hole concentration decreases by several times. The results are explained by assuming a formation of an ytterbium-induced deep defect level in the energy spectrum of the alloys, which moves up to the top of the valence band with increasing the ytterbium concentration and pins the Fermi level within the valence band at sufficiently high impurity content. The hole concentration vs. ytterbium content dependence was used to calculate the energy position of the Fermi level in the frame of two-band dispersion law and to determine the position of Yb level in the alloys. The diagram of the charge carrier energy spectrum under varying the alloy composition was built.

Study of the electronic properties of some ytterbium filled skutterudites by magnetic susceptibility and x-ray absorption and tin-119 Mössbauer spectroscopy

Magnetic susceptibility, ytterbium LIII-edge x-ray absorption and tin-119 Mössbauer spectral measurements have been carried out to probe the electronic structure of ytterbium and tin in the filled or partially filled skutterudite compounds, YbyCo4Sb12−xSnx, over a range of x and y values. The ytterbium valence obtained from the magnetic susceptibility and ytterbium LIII-edge x-ray absorption measurements is in excellent agreement and clearly reveals an evolution from intermediate valence ytterbium for x=0 to nearly divalent ytterbium for x=0.8. This evolution parallels an increase in the unit cell volume and hence in the ytterbium site volume available as the tin content increases. The tin-119 Mössbauer spectral hyperfine parameters indicate, without question, that tin substitutes on the antimony sublattice of the skutterudite structure. Further, the tin electronic configuration is both very similar to that of the antimony in the structure and insensitive to the ytterbium content, y.