Lu Doping Research Articles

Observation of magnetic dimers in the diluted triangular-lattice spin liquid candidate NaYbO2

The triangular-lattice spin liquid (QSL) candidate NaYbO2 is magnetically diluted by Lu doping, forming homogeneous solid solutions NaYb1-xLuxO2 (0≤ x<1.0). A combination of structural, magnetic, and pulsed high-field electron spin resonance analysis shows that the lattice parameters and the Curie-Weiss temperature θCW vary almost linearly with x, and the crystal electric field environment of the Yb/Lu ions persists during the Lu doping. The statistical distribution analysis of clusters and the deduced linear θCW ∼ x relation indicate that the nearest neighbor exchange J does not change with magnetic dilution. Interestingly, with the magnetization measurement at 0.39 K, we have observed Seff = 1/2 antiferromagnetic Yb-Yb dimers in NaYb0.02Lu0.98O2, which is manifested as a magnetization step at μ0Hc = 2.68 T due to the transition between singlet and triplet states. Thus, the intradimer interaction is directly determined as J/kB = −5.15 K. Surprisingly, this value is close to the interaction of undoped NaYbO2, supporting the theoretical analysis of clusters. Our study provides a method of estimating the magnetic interaction of QSL materials through magnetic dilution. The statistical distribution analysis of magnetic clusters suggests that through a small amount of Lu doping (x < 0.5), the QSL state in NaYbO2 can continue to be maintained.

Doping effect on structural, morphological and magnetic properties of YbMnO3 compound with non-magnetic Lutetium ion

The present study presents an analysis of the structural, morphological and magnetic properties of multiferroic YbMnO3 (YBO) due to Lu doping. YbMnO3 (YBO) and Yb0.85Lu0.15MnO3 (YBLu) were prepared using a conventional solid state reaction method. The investigation employed techniques such as X-ray diffraction (XRD), Field Effect Scanning Electron Microscope (FE-SEM), Raman spectroscopy and magnetic measurements. The X-ray diffraction (XRD) patterns of both samples confirmed the growth of these samples in a polycrystalline single hexagonal phase having space group P63cm with no detectable impurities. The evaluation of crystalline parameters, such as lattice parameters, cell volume, specific bond lengths etc. has been carried out. The Lu-doped sample shows a minor reduction in cell parameters and cell volume which can be attributed to the smaller ionic radius of Lu3+. Lu doping in YBO results in slight shift in Raman Lines towards slightly frequencies which is the result of a small change in the average bond length. The effective magnetic moment of YBLu is found to decrease ∼6 % and the antiferromagnetic ordering temperature TN nearly remains the same because Lu3+ has zero magnetic moment. Both samples show ferri/ferromagnetic behaviour below 5 K due to the ordering of the Yb3+ lattice.

Lu2O3–Y2O3–ZrO2: A Lu3+ co-doped YSZ system—Oxygen-ion conductor with high electrical conductivity and improved mechanical properties

This study investigates the electrical and mechanical properties of a Lu2O3–Y2O3–ZrO2 system (ZrO2 co-doped with Lu2O3 and Y2O3) and evaluates its possibility for use as a high-performance oxygen-ion conducting ceramic suitable for intermediate/high-temperature solid electrolytes. The use of electrochemical impedance spectroscopy (EIS) in the analysis and fitting of AC impedance spectra arcs on 8 mol% (Lu2O3–Y2O3)– ZrO2 has allowed to compare with the Y2O3-doped ZrO2 (YSZ) and Sc2O3-doped ZrO2 (ScSZ). (ZrO2)0.92(Y2O3)0.07(Lu2O3)0.01, with 1 mol% Lu2O3 co-doped with Y2O3, shows a bulk conductivity of 9.60 × 10−1 S/cm at 1000 °C and 3.47 × 10−2 S/cm at 800 °C, which are least several times higher than the corresponding values of any other sample in the experimental group, including Sc2O3-doped ZrO2, over the entire measured temperature range. (ZrO2)0.92(Y2O3)0.075(Lu2O3)0.005 also shows an outstanding conductivity; over two times higher than that of ScSZ. Thus, Lu2O3 co-doping can enhance mechanical properties such as flexural strength (19.5 % (1 mol% Lu2O3) and 21.5 % (2 mol% Lu2O3) higher than that of YSZ), as confirmed by the flexural strength and Vickers hardness tests. After 8 mol% sesquioxide doping of YSZ, the maximum improvement in the electrical and mechanical properties occurs at approximately 1 mol% (for electrical properties) and 2 mol% (for mechanical properties) Lu2O3 co-doping, respectively. The results of this work suggest that a small amount of Lu doping, performed during the development of materials for use in electrochemical devices (including high-efficiency energy conversion apparatus), could be a considerable approach to overcome the limitations of conventional solid oxide electrolytes.

The impact of lutetium doping on the structure and physical characteristics of aluminum arsenide quantum dots

This report mentioned the synthesis of self-assembly Al1-xLuxAs quantum dot nanocrystals using the L-Glutamine-assisted wet chemical route. The effect of Lu-doping on the structural phase, lattice strain, and deformation lattice energy was studied. The morphology and elemental compositions were emphasized using transmission electron microscopy, selected area of electron diffraction, and energy dispersive X-ray spectroscopy. The effect of Lu-doping on the oxidation state and vibrational modes was studied using X-ray photoelectron spectroscopy and Raman scattering spectroscopy. The influence of Lu-dopant on the optical bandgap and Urbach tail energy of AlAs nanocrystals was investigated. The tendency of Lu doping to create localized levels inside the band gap of AlAs gives rise to an increase in plasma frequency and a decrease in the high-frequency dielectric constant. The Lu-dopant improved the conductivity and the charge carrier mobility of AlAs nanocrystals. The luminescence measurements revealed the ability of Lu-dopant to suppress the crystal defects of the AlAs nanocrystals. The Lu doping improved the quantum yield (84 %) and the luminescent emission spectra of the AlAs QDs by 7-fold. The prepared self-assembly Al1-xLuxAs quantum dots revealed great encouragement for developing Al1-xLuxAs quantum dot diode lasers and optical broadbands.

Improved ultraviolet -visible optically transmittance and luminescent properties in Yb, Lu: Sr5(PO4)3F transparent ceramics via Lu3+ co-doping

The asymmetric hexagonal Sr5(PO4)3F (S-FAP) crystal material is considered to be the most suitable solid state laser gain medium for small laser diode pumping in the future due to its large absorption, emission interface, and long fluorescence lifetime. However, the mediocre optical transmittance of S-FAP transparent ceramics and the degradation of luminescence properties due to the doping of Yb activated ions seriously hinder its application prospects. In view of this, a series of 0.02Yb, xLu: S-FAP (x = 0–0.02) transparent ceramics with excellent optical properties were synthesized by hot pressing sintering. The powder SEM results show that Lu doping has no obvious effect on the morphology, grain size, and dispersion of powder. The linear transmissivity curves show that the ultraviolet (200 nm) and visible (500 nm) transmissivity increase by 54 % and 17 %, respectively, with Lu doping compared with the undoped ceramic samples. The surface SEM of ceramics revealed that Lu3+ promoted the increase of ceramic grain size significantly. The emission spectrum and fluorescence decay curves at room temperature also show that the emission intensity and fluorescence lifetime of ceramic samples increase significantly with Lu co-doping.

Engineering of Vacancy Defects in WS2 Monolayer by Rare‐Earth (Er, Tm, Lu) Doping: A First‐Principles Study

Vacancy defects in two‐dimensional (2D) materials are critical to their properties. The substitutional doping in vacancy defects by rare‐earth atoms results in diverse material versatilities, but the effects and the corresponding mechanisms are far from being answered. Herein, the electronic and optical properties of vacancy defects and lanthanide rare‐earth (RE = Er, Tm, Lu) doping in WS2 monolayers are studied based on density functional theory with Hubbard correction (DFT + U). The formation energies of defective and doped systems are calculated under W‐rich and S‐rich conditions, respectively. The bandgap of WS2 with one W‐defect in a 4 × 4 × 1 supercell changes from direct to indirect, while S‐defect does not change the bandgap type of the supercell. When RE atoms are doped in the W‐defect, the bandgap returns to direct. WS2 supercells with intrinsic defects and Lu doped in [W] defect show the nonmagnetic property, while Er‐ and Tm‐doped supercells show obvious magnetic properties. The imaginary part of dielectric function and absorption coefficients increase drastically from visible to near‐infrared as RE atoms substitute W sites, and the bandgap shrinks due to the rise of the valance band maximum. This work proves RE doping in 2D WS2 is an effective technique for bandgap and carrier engineering.

Lu doping nickel oxide thin films using sol-gel spin coated and density functional theory: optoelectronic and magnetic properties

For the first time, sol-gel spin coating was used to fabricate thin films of NiO doped with lutetium. The films were characterized to determine their crystalline structure, surface morphology, and optical properties as a function of Lu doping concentration. The investigations revealed that the Lu-doped NiO films consisted of nano-polycrystalline particles with a cubic bunsenite structure and (200) preferential orientation. Optical studies indicated that the optical band gap of pure NiO widened with low levels of Lu incorporation before narrowing with higher concentrations. The Urbach energy value for pure NiO initially decreased with 1 at. % Lu-content, from 224 meV to 190 meV, and then continuously increased to 380 meV with more Lu-level. To investigate the effects of Lu doping on the electronics, magnetic, and optical properties of NiO, first-principle computations were performed. The results showed that bulk magnetization underwent significant modifications due to a high hybridization between the Lu-f/d and Ni-d states. This study suggests that NiO doped with lutetium could be used for spin-polarized transport devices and other spin-dependent applications.

Oxide nanoparticle exsolution in Lu-doped (Ba,La)CoO3

This study investigated Lu doping of Ba0.5La0.5CoO3 and its influence on the exsolution of oxide nanoparticles (NPs).

Sol–gel spin coating derived cadmium oxide semiconductor thin films: Effect of Lutetium contribution

Continuously developing optoelectronic technology requires alternative transparent conductive oxide (TCO) materials. Due to their high optical transmittance and conductivity, TCO materials have many application areas. Cadmium oxide (CdO) thin films, one of the most important TCO materials, are frequently used in optoelectronic technology. In this study, pure and Lu doped CdO semiconductor thin films with 1, 2, 3, 4, and 5 at% concentrations were produced using the sol- gel spin coating technique. The changes in the optical, structural and surface properties of the films were examined as a function of the doping and it was determined that the doping process caused significant changes in the properties of the films. The XRD results showed that the samples were polycrystalline cubic and the average crystallite size varied between 13.42 nm and 26.39 nm with Lu contribution. To examine the optical properties of CdO: Lu thin films, the transmittance and absorption spectra of the films were taken in the UV–VIS region. The optical absorption coefficient, refractive indexes, dielectric constants, optical-electrical conductance, and optical band-gap of films were calculated by using the obtained transmittance and absorption spectra, and the effect of doping on the optical properties of the films was investigated. Depending on the amount of Lu, some fluctuations are observed in Eg values. It was determined that Lu doping from the changes in SEM is effective in changing the properties of CdO and these films are suitable materials for sensor and display applications. SEM images revealed that the Lu contribution rate caused the surface change of thin films. With this study, the effect of Lu doping on structural, optical, and superficial properties of CdO films was investigated and it was determined that Lu doping of CdO films were suitable materials for optoelectronic applications.

Effect of Lu doping on the structure, electrical properties and energy storage performance of AgNbO3 antiferroelectric ceramics

Recently, AgNbO3 antiferroelectric ceramics have attracted great attention by virtue of their characters of high energy storage density and environmental friendliness. To further optimize the electrical properties, in this work, Lu2O3 modified AgNbO3 ceramics were prepared via conventional solid state method. Crystal structure and element analysis indicated the Lu3+ ion preferred to enter the A-site when Lu2O3 content was lower than 2 mol%, otherwise, it was more likely to form LuNbO4 or Lu3NbO7-based solid solutions. Remarkably improved stability of antiferroelectric phase was observed once Lu3+ ions enter into the A-site, on account of the decrease of cell volume and tolerance factor. As a consequence, an enhanced recoverable energy storage density (Wrec) of 3.5 J/cm3 was achieved in 1 mol% Lu2O3 modified AgNbO3 ceramics at 210 kV/cm, which is superior to the other lead-free ceramics under moderate electric field (< 220 kV/cm). It is believed our study will provide a good reference for the development of AgNbO3-based dielectric capacitors.

Designing High‐Performance LED Phosphors by Controlling the Phase Stability via a Heterovalent Substitution Strategy

AbstractPhosphor‐converted white light‐emitting diodes (LEDs) are currently playing key roles in the lighting and display industries and trigger urgent demands for the discovery of “good” phosphors with high quantum efficiency, improved thermal stability, and controllable excitation/emission properties. Herein, a general and efficient heterovalent substitution strategy is demonstrated in K2HfSi3O9:Eu2+achieved by Ln3+(Ln = Gd, Tb, Dy, Tm, Yb, and Lu) doping to optimize luminescence properties, and as an example, the Lu3+substitution leads to improvement of emission intensity and thermal stability, as well as tunable emission color from blue to cyan. The structural stability and Eu2+occupation via Lu3+doping have been revealed by the structural elaboration and density functional theory calculations, respectively. It is shown that heterovalent substitution allows predictive control of site preference of luminescent centers and therefore provides a new method to optimize the solid‐state phosphors for LEDs.

Enhanced thermoelectric properties of the Lu-doped and CNT-dispersed Bi2Te3 alloy

Bi2Te3 and Lutetium-doped Lu0.1Bi1.9Te3 nanopowders were prepared by the hydrothermal method. Different amounts of carbon nanotubes (CNTs) were dispersed into Lu0.1Bi1.9Te3 nanopowders and hot pressed into bulk samples with nominal chemical formula of Lu0.1Bi1.9Te3 + xwt% CNT (x = 0, 0.05, 0.1, 0.5, 1) to assess the effects of lutetium doping and CNT dispersing on the thermoelectric properties. The electrical resistivity decreased because of the increase of the carrier concentration and carrier mobility at a low CNTs content. Herein, a small amount of CNTs were used as conducting filler to provide a free path of carriers which would lead to an increase of carrier mobility, though a large number of CNTs mainly played an energy-filtering effect. The thermal conductivity of Lu0.1Bi1.9Te3 + xwt% CNT nanocomposite showed an evident decrease, which resulted from the enhanced phonon scattering by the point defects caused by Lu doping and the interfaces between Lu0.1Bi1.9Te3 and CNTs. Due to the decrease in the electrical resistivity and thermal conductivity, the figure of merit (ZT) of Lu0.1Bi1.9Te3 + 0.05 wt% CNT nanocomposite was higher than that of Bi2Te3 and Lu0.1Bi1.9Te3 when the temperature was below 473 K.

Handling magnetic and structural properties of EuMnO3 thin films by the combined effect of Lu doping and substrate strain

This work aims to understand the alterations induced by film/substrate lattice mismatch in structure, lattice dynamics and magnetic response of orthorhombic Eu1-xLuxMnO3 thin films within the range 0 ≤ x ≤ 0.4, when compared to results reported for ceramics with analogous composition. Thin films, which have been deposited onto Pt/Ti/SiO2/Si(100) oriented substrates via chemical method, exhibit noteworthy modifications in the magnetic ordering properties and, contrary to ceramics, do not show any sharp phase transition to the paramagnetic state. This reveals an induced ferromagnetic response in the films which is stable up to 100 K. X-ray diffraction and Raman spectroscopy measurements have been performed to identify the mechanically compressive state induced by the substrate and Lu doping. This facilitates insight into the magnetoelastic coupling effect in these films which is driven by alterations in electronic orbital overlapping and the associated antiferromagnetic superexchange interactions.

Mechanisms of thermoelectric efficiency enhancement in Lu-doped Bi2Te3

The LuxBi2−xTe3 thermoelectrics with x = 0, 0.05, 0.1 and 0.2 have been prepared by microwave-solvothermal method and spark plasma sintering. All the compositions are semiconductors of n-type conductivity. It was found that electron concentration increases and electron mobility decreases with x increasing. The Lu doping results in remarkable increase of the thermoelectric figure-of-merit from ∼0.4 for undoped Bi2Te3 up to ∼0.9 for Bi1.9Lu0.1Te3. Enhancing the thermoelectric efficiency at the doping is originated from: (i) increase of the electron concentration since the Lu atoms behave as donors in the Bi2Te3 lattice that decreases the specific electrical resistance, (ii) increase of the Seebeck coefficient via increase of the density-of-states effective mass for conduction band, (iii) decrease of the total thermal conductivity via forming the point defects like antisite defects and Lu atoms substituting for the Bi sites. Formation of narrow non-parabolic impurity band lying near the Fermi energy with sharp density of states is believed to be responsible for increasing the density-of-states effective mass and decreasing the electron contribution to the total thermal conductivity.

Effects of Lu and Tm Doping on Thermoelectric Properties of Bi2Te3 Compound

The Bi2Te3, Bi1.9Lu0.1Te3 and Bi1.9Tm0.1Te3 thermoelectrics of n-type conductivity have been prepared by the microwave-solvothermal method and spark plasma sintering. These compounds behave as degenerate semiconductors from room temperature up to temperature T d ≈ 470 K. Within this temperature range the temperature behavior of the specific electrical resistivity is due to the temperature changes of electron mobility determined by acoustic and optical phonon scattering. Above T d, an onset of intrinsic conductivity takes place when electrons and holes are present. At the Lu and Tm doping, the Seebeck coefficient increases, while the specific electrical resistivity and total thermal conductivity decrease within the temperature 290–630 K range. The increase of the electrical resistivity is related to the increase of electron concentration since the Tm and Lu atoms are donor centres in the Bi2Te3 lattice. The increase of the density-of-state effective mass for conduction band can be responsible for the increase of the Seebeck coefficient. The decrease of the total thermal conductivity in doped Bi2Te3 is attributed to point defects like the antisite defects and Lu or Tm atoms substituting for the Bi sites. In addition, reducing the electron thermal conductivity due to forming a narrow impurity (Lu or Tm) band having high and sharp density-of-states near the Fermi level can effectively decrease the total thermal conductivity. The thermoelectric figure-of-merit is enhanced from ∼ 0.4 for undoped Bi2Te3 up to ∼ 0.7 for Bi1.9Tm0.1Te3 and ∼ 0.9 for Bi1.9Lu0.1Te3.

Enhancement of thermoelectric efficiency in Bi2Te3 via rare earth element doping

The Bi2Te3, Bi1.9Lu0.1Te3 and Bi1.9Tm0.1Te3 thermoelectrics of n-type conductivity were prepared by microwave-solvothermal method and spark plasma sintering. At the Lu and Tm doping, the Seebeck coefficient increases, while the specific electrical conductivity and total thermal conductivity decreases resulting in thermoelectric efficiency enhancement of Bi2Te3. It is believed that the thermoelectric efficiency can enhance mainly due to formation of narrow impurity Lu or Tm band with high and sharp density of states near the Fermi level. Both increase of the density-of-states effective mass of electrons and decrease of electronic contribution to the total thermal conductivity take place in this case.

Thermoelectric properties of Lu-doped n-type LuxBi2-xTe2.7Se0.3 alloys

Lutetium-doped LuxBi2-xTe2.7Se0.3 (x = 0–0.3) nanopowders were synthesized by the hydrothermal method, and then they were hot-pressed into bulk pellets at 773 K under a pressure of 60 MPa in vacuum. The doping effects of Lutetium on the thermoelectric properties were investigated. Compared with the undoped sample, the electrical resistivities of Lu doped samples increased, and the Seebeck coefficients increased slightly. The lower carrier mobility caused by scattering may be the reason for the increase of the electrical resistivities of the doped samples. The thermal conductivities were significantly reduced because the Lu doping introduces a number of point defects into the crystals, which can effectively enhance phonon scattering, and because smaller grain size caused by Lu doping can enhance interface scattering. As a result, all the Lu doped LuxBi2-xTe2.7Se0.3 samples show higher ZT values compared with the undoped samples, indicating that Lu doping is an efficacious way to improve the thermoelectric properties of the n-type Bi2Te2.7Se0.3 alloys.

Microstructure and performance of rare earth element-strengthened plasma-facing tungsten material.

Pure W and W-(2%, 5%, 10%) Lu alloys were manufactured via mechanical alloying for 20 h and a spark plasma sintering process at 1,873 K for 2 min. The effects of Lu doping on the microstructure and performance of W were investigated using various techniques. For irradiation performance analysis, thermal desorption spectroscopy (TDS) measurements were performed from room temperature to 1,000 K via infrared irradiation with a heating rate of 1 K/s after implantations of He+ and D+ ions. TDS measurements were conducted to investigate D retention behavior. Microhardness was dramatically enhanced, and the density initially increased and then decreased with Lu content. The D retention performance followed the same trend as the density. Second-phase particles identified as Lu2O3 particles were completely distributed over the W grain boundaries and generated an effective grain refinement. Transgranular and intergranular fracture modes were observed on the fracture surface of the sintered W-Lu samples, indicating some improvement of strength and toughness. The amount and distribution of Lu substantially affected the properties of W. Among the investigated alloy compositions, W-5%Lu exhibited the best overall performance.

Optimization of the spin entropy by incorporating magnetic ion in a misfit-layered calcium cobaltite

Effects of (Lu, Ni) co-doping on spin entropy of Ca3Co4O9+δ have been investigated. Results of this study show that (Lu, Ni) co-doping can be more effective than single Lu doping for optimizing the spin entropy of Ca3Co4O9+δ. X-ray photo-emission spectroscopy confirms a reduction in Co4+ concentration, which leads to enhanced spin entropy from Co sites. The magnetic ions of Ni with unpaired 3d electrons can produce extra spin entropy through a new hopping model, thereby contributing to an increase in total spin entropy. Incorporating magnetic ions is an effective way to optimize the spin entropy of thermoelectric materials. This study opens a new way to broaden and design prospective thermoelectric materials.

Fabrication and Scintillation Performance of Nonstoichiometric LuAG:Ce Ceramics

Nonstoichiometric LuAG:Ce Ceramics ([Lu(1–x)Cex]3Al5O12, x = 0.005) with different excess of Lu3+ were designed on the basis of Lu2O3‐Al2O3 phase diagram and fabricated by a solid‐state reaction method. Without using any traditional sintering aids, pure phase and good optical performance were obtained in such a Lu‐rich LuAG:Ce ceramics. In addition, scintillation efficiency and light yield of 1% excess of Lu3+ ceramic sample were found 16 times and 1.82 times higher than that of commercial Bi4Ge3O12 (BGO) single crystals, respectively. Such values are comparable or even better than those in most of LuAG:Ce single crystals. However, antisite defects were also induced by excess of Lu doping, whose luminescence was found at 350–410 nm in Lu‐rich LuAG:Ce ceramics. The relationship of excess content of Lu and the microstructure, optical quality, and scintillation performance were clarified and discussed. Furthermore, by utilizing X‐ray absorption near edge spectroscopy technique, the charge state stability of cerium in Lu‐rich LuAG:Ce ceramics was examined. It appears that the excess of isovalence Lu3+ doping has a negligible effect on the cerium valence instability and creation of stable Ce4+ center.