Increasing Eu Concentration Research Articles

Structural and optical properties of Eu3+-doped sol–gel silica–soda glasses

Rare earths (REs) incorporated in glasses, mostly in the form of RE3+ ions, have several applications such as lasers and optical amplifiers, spectral conversion layers for solar cells, light emitters and sensors. In this context, both the composition and the structural properties of the glass, as well as the dopant concentration play an important role in determining the optical properties and the efficiency of the system. Usually, the concentration of REs is small, below 1 at%, to avoid clustering and optical quenching. In this paper, we report the case of sol–gel Eu-doped silica–soda glass films. The addition of soda to silica can reduce RE clustering and precipitation, according to molecular dynamic simulations, but brings structural instabilities to the network. Here, sodium was varied from 10 to 30 at% and Eu from 0 to 8 at%. It was shown that Eu plays a significant role in the stabilization of the matrix, improving the transparency, the refractive index and the thickness of the films. The increase of Eu concentration provides a decrease of site symmetry and an increase of quantum efficiency (QY), reaching 71% for the highest 8 at% Eu doping, with remarkable absence of concentration quenching.

Connecting visual metamictization to radiation damage to expand applications of zircon (U-Th)/He thermochronometry

Zircon (U-Th)/He (ZHe) thermochronometry quantifies the timing and tempo of low-temperature processes and is used to deconvolve tectonic and erosional histories. Accumulation and annealing of radiation damage impacts He diffusion in zircon and resulting ZHe dates. Resolving complex histories requires building relationships between ZHe date, effective U (eU), and radiation damage in grains sharing a common thermal history. Prior work demonstrated that purposefully selecting grains with a spectrum of visual metamictization yields a broad range of intrasample eU values (Ault et al., 2018), but it remained unclear if visual metamictization tracks effective radiation damage. Here we evaluate relationships between visual metamictization, effective damage calculated from Raman spectroscopy, and ZHe dates from a new suite of grains from some of the same Precambrian samples investigated in Ault et al. (2018) and Phanerozoic detrital grains from Armstrong et al. (2022). New ZHe analyses (n = 21) confirm increasing visual metamictization corresponds with increasing eU concentration and dates fall along previously reported ZHe date-eU trends for each sample, despite grain selection by different analysts in different sessions. Raman-based alpha dose calculations from multiple spot analyses from transects across the surface and interior of each grain (n = 480 total analyses) range from 3.19 × 1016 to 1.52 × 1019 α/g across the whole dataset. Alpha dose increases in samples characterized by a clear increase in visual metamictization from different types of ZHe date-eU patterns, supporting that visual metamictization reflects effective radiation damage in these samples. Complexities in visual metamictization-damage trends are due to damage zonation observed in cathodoluminescence, comparative internal and external spot analyses, and 2-D Raman maps, as well as limited spread in intrasample visual metamictization and user grain selection bias. Overall, visual metamictization provides a qualitative estimate of effective damage and should be leveraged when selecting grains for traditional ZHe analyses to build ZHe date-eU-damage patterns.

Optical and scintillation properties of the Eu2O3-doped HfO2-Al2O3–SiO2 glass ceramics

In this study, Eu-doped 10HfO2–10Al2O3–80SiO2 glass ceramics with different Eu concentrations were prepared by the melt-quenching method using an optical floating zone furnace, and optical and scintillation properties were investigated to apply them for radiation detectors. All the glass ceramic samples were transparent, although they included not only an amorphous phase but also a crystal phase of cubic-HfO2. Photoluminescence and scintillation peaks due to Eu2+ were detected at 400–550 nm. In the glass ceramic samples with higher Eu concentration, the luminescence of Eu3+ was also observed. Quantum yields and afterglow levels decreased with increasing Eu concentration. The 1.0% Eu-doped sample had the highest light yield among all our glass samples, and the light yield was 630 photons/MeV under γ-ray irradiation from 137Cs.

Enhancement of electrical properties in Eu-doped PMN-PT thin films prepared by sol-gel method

Europium-modified Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 (xEu-PMNT) (x = 1 %, 2 %, 3 %, 4 %) thin films have been deposited on Pt/Ti/SiO2/Si substrates via sol-gel process. The purpose of this present work was to investigate Eu doping-dependent crystal orientation, microstructure, and piezoelectric behaviors of the Eu-PMNT films. X-ray diffraction (XRD) analysis shows that PMNT films exhibit (100) preferred orientation when Eu content less than 3 %, and the film doped with 4 % show (110) polycrystalline orientation accompanied by pyrochlore phase. Increasing grain size and dense microstructure are detected by Scanning electron microscope (SEM) characterization as increasing Eu concentration to 2 %. For the film with 2 % Eu-doped, superior dielectricity (εr = 1204.5, tanδ = 0.055) measured at 1 kHz and ferroelectricity (2Pr = 21.6 μC/cm2, 2Ec = 73 kV/cm) are achieved. Moreover, an enhanced piezoelectric constant (e31) of 8.2 C/m2 is obtained in the PMN-PT film doped with 2 % Eu.

Synergistic effects of Eu and Nb dual substitution on improving the thermoelectric performance of the natural perovskite CaTiO3

Driven by the development of sustainable and regenerable energy conversion materials, the mineral perovskite (CaTiO3) is considered to be a potential candidate for large-scale high-temperature applications owing to its abundance, light-weight, non-toxicity, and low cost. A series of compounds with the nominal composition Ca1–xEuxTi0.9Nb0.1O3 (0 ≤ x ≤ 0.4) has been synthesized and studied in this paper. The phase purities and crystal structures were evaluated by powder X-ray diffraction (XRD) and subsequent Rietveld analysis. Through X-ray photoelectron spectroscopy (XPS) characterization, the by far dominating valence states of Ti and Nb are confirmed to be +4 and + 5 in Ca1-xEuxTi0.9Nb0.1O3 compounds, respectively. Dual substitution by Nb and Eu yields a synergistic effect of improving electrical transport properties and simultaneously suppressing thermal conductivity. The former is mainly attributed to the d–f electron exchange induced by the strong hybridization of Eu 4f, Nb 4d, and Ti 3d orbitals. The latter is mostly attributed to the dominant phonon scattering by the mass fluctuation originating from the large mass contrast of Eu and Ca. The results demonstrate the evolution of insulating CaTiO3 to metallic-like conduction performance with increasing Eu content. Due to the largest power factor and lowest thermal conductivity, the sample Ca0.8Eu0.2Ti0.9Nb0.1O3 exhibits the maximum ZT of up to 0.3 at around 1173 K.

Effect of Eu Doping on Structural, Optical and Magnetic Properties of BiFeO3 Materials

Bi1-xEuxFeO3 (BEFO) (x = 0.00 ÷ 0.10) materials were prepared by sol-gel method. The crystal structural, Raman scattering, magnetic and optical properties of BEFO were investigated by X-ray diffraction (XRD), Raman scattering spectroscopy, magnetic hysteresis (M-H) loops and fluorescence spectroscopy (FL), respectively. Obtained results of the characterization showed that Eu-doping affected structural, optical and magnetic properties of BFO materials. All samples were crystallized in the rhombohedral structure with R3C space group with crystal lattice parameters of a = 5.585 Å, c = 13.832 Å and the average crystal size of LXRD = 581 Å for BFO materials whereas the a, c and LXRD of Eu-doped samples decrease with the increasing of Eu3+ concentration. The analysis result of Raman scattering spectroscopy showed that the position of the characteristic peak for Bi-O covalent bonds shifts toward higher frequency when Eu3+ concentration increases, confirming the dopping substitution of Eu3+ ions into Bi-sites. Fluorescence spectra showed the enhancement of characteristic emission peaks with the increase of Eu concentration. All samples exhibited weak ferromagnetic behaviour with saturation magnetization of Ms = 0.006 emu/g and remnant magnetization of Mr = 0.004 emu/g for BFO materials. The value of Ms and Mr of Eu-doped BFO increases compared to those of undoped-BFO. The origin of ferromagnetism and fluorescence improvement has been discussed.

Sm-Eu Co-Doped BiFeO3 Nanoparticles With Superabsorption and Electrochemical Oxygen Evolution Reaction

Bi0.95Sm0.05Fe1−xEuxO3 (x = 0, 0.05, 0.10, 0.15) nanoparticles were prepared via a two-solvent sol–gel method. The X-ray diffraction (XRD) and Raman results suggested that the main phase of the samples gradually evolved from perovskite phase R3c to orthorhombic phase Pbnm with increasing Eu content and that the optical band gap gradually narrowed from 2.09 to 1.70 eV. Along with the structural change, the ferromagnetic properties were transformed, and interesting double hysteresis loops were observed for the sample where x = 0.1. All the bismuth ferrite (BFO) samples demonstrated extremely strong adsorbability, with the adsorption rate of refractory methyl orange reaching 90% in 5 min. These samples also exhibited superior oxygen evolution reaction (OER) performance, with a desirable onset potential of approximately 1.50 V vs. RHE. For the sample where x = 0.15, to support a current density of 100 mA/cm2, an overpotential of only 294 mV was required, which is much better than that of pure Ni foam (330 mV). More experiments are needed to verify and explore the source and mechanism of the OER performance.

A correlation of piezoelectricity and photoluminescence of europium doped (Na0.41K0.09Bi0.5)TiO3 with ferroelectric and structural ordering

A correlation between piezoelectricity and photoluminescence is investigated for europium doped (Na 0.41 K 0.09 Bi 0.5 )TiO 3 ceramic. An optimum piezoelectric and dielectric response is observed for 1.0 at.% Eu doped (Na 0.41 K 0.09 Bi 0.5 )TiO 3 . For doping concentration higher than 1.0 at.% a gradual fall in the piezoelectric response is observed which is associated to the amphoteric nature of Eu 3+ ion. On the contrary, the photoluminescence intensity increases monotonically with the increase in Eu concentration. On application of an electric field, although there is no noticeable shift in the position and shape of the photoluminescence line, a quenching of hypersensitive 5 D 0 → 7 F 2 transition is observed. The quenching effect is more evident for lower doping concentration (less than 2.0 at.%) of europium. The emergence of irreversible tetragonal phase, after application of the electric field, is attributed to the quenching of 5 D 0 → 7 F 2 transition. Based on these investigations it is concluded that the piezoelectric and photo-luminescence lack one-to-one correlation. The PL response is associated to the local site symmetry around Eu 3+ and it is independent of the development of long-range ordering.

Effects of Eu modification and heat treatment on microstructure and mechanical properties of hypereutectic Al–Mg2Si composites

To modify the coarse primary Mg2Si phase and improve mechanical properties of Mg2Si reinforced aluminum matrix composites, hypereutectic Al–18Mg2Si composites with different Eu contents were fabricated by permanent mold casting and extrusion followed by heat treatment. Results show that the as-cast Al–18Mg2Si composites consisted of primary Mg2Si and eutectic structure (Al + Mg2Si). Eu addition can obviously modify the primary Mg2Si morphology from dendrite to flat truncated octahedron shape, and the average size also decreased from ∼90 μm to ∼16 μm with increasing Eu content from 0 to 0.1%. But further increasing Eu content would cause over-modification. After T6 treatment, sharp corners of primary Mg2Si were spheroidized and the average size of primary Mg2Si were further decreased. DTA result shows the nucleation temperature of primary Mg2Si increased by Eu addition. Al2Si2Eu phase can act as the heterogeneous nucleation substrate for the primary Mg2Si phase and thus refine the size of primary Mg2Si particle. TEM results show the segregation and/or selective adsorption of Eu on the {100} facets of primary Mg2Si suppress the growth of primary Mg2Si, and thus refine and modify the composites, which proposed to the dominant reason for the refinement and modification of the primary Mg2Si phase. Tensile tests show that the mechanical properties enhanced with increasing Eu content. The elongation and ultimate tensile strength of the T6-treated Al–18Mg2Si-0.1Eu composite improved to 5.2% and 241 MPa, which enhanced 225% and 91% compared to the unmodified as-cast Al–18%Mg2Si composite. It is concluded that the morphology transition of primary Mg2Si from dendrite to tetrakaidecahedron and the refinement of primary Mg2Si size with Eu modification, the passivation of the sharp corners in primary Mg2Si particles as well as the appearance of β" precipitates all contribute to the improvement of the mechanical properties of the T6-treated Al–18Mg2Si composites.

An investigation of structural, electrical and optical properties of lead-free barium zirconium titanate (BZT)-based ceramic compounds

ABSTRACT The present work is a demonstration of improved electrical and optical properties of barium zirconium titanate ceramic modified by the addition of Europium, i.e. Ba(1–x)Eu2x/3Zr0.05Ti0.95O3 (x = 0.01, 0.02, 0.03, 0.04). The Rietveld refinement studies confirmed the formation of tetragonal phase in the samples. The scanning electron microscopy (SEM) images revealed a decrease in grain size with increasing Eu concentration. The dielectric constant, dielectric loss and TCC plots are drawn to study temperature and frequency dependence of the samples. The electric field-induced strain behavior has been studied for all the compositions of the synthesized ceramic at room temperature. Conduction mechanism in the samples as a function of frequency and temperature was studied with the help of AC conductivity data. Also, the effect of grain and grain boundaries are studied in term of Cole–Cole plots. Photoluminescence (PL) emission spectra were recorded upon excitation with a wavelength of 360 nm.

Improvement of superconducting properties by chemical pressure effect in Eu-doped La2-xEuxO2Bi3Ag0.6Sn0.4S6

We have investigated the substitution effect of Eu on the superconductivity in La2-xEuxO2Bi3Ag0.6Sn0.4S6. Recently, we reported an observation of superconductivity at 0.5 K in a layered oxychalcogenide La2O2Bi3AgS6. The Sn doping at the Ag site was found to raise the superconducting transition temperature, Tc, to 2.5 K in La2O2Bi3Ag0.6Sn0.4S6. To further improve the superconducting properties, we have partially substituted Eu for the La site to increase the chemical pressure in La2-xEuxO2Bi3Ag0.6Sn0.4S6 (x = 0.1–0.6). La2-xEuxO2Bi3Ag0.6Sn0.4S6 is crystallized in a tetragonal phase with the space group P4/nmm. With the increase in Eu concentration, x, the lattice constant a decreased, while the lattice constant c was marginally shortened, which suggests that the chemical pressure induced by the Eu doping is uniaxial along the a-axis. Tc increased with increasing x up to x = 0.4, and the suppression of superconductivity was observed for higher Eu concentrations of x = 0.5 and 0.6. From the magnetic susceptibility and resistivity measurements, a superconducting transition has been confirmed for x = 0.1–0.6 with Tc = 2.5–4.0 K, respectively. The estimated upper critical field (Bc2) was 3.5 T for x = 0.4, which also has the highest Tc. We observed the jump in the temperature dependence of heat capacity near Tc = 4.0 K for La1.6Eu0.4O2Bi3Ag0.6Sn0.4S6, which confirms the emergence of bulk superconductivity in La1.6Eu0.4O2Bi3Ag0.6Sn0.4S6.

Rietveld analysis and negative dielectric behavior of perovskite-like La1–xEuxMnO3 system

In this article, we report the results of the Rietveld and impedance analysis of Eu doped La1–xEuxMnO3 (LEMO; x = 0.10, 0.30, and 0.50) perovskite manganites synthesized by solid-state reaction method. Structural studies through Rietveld analysis confirm that a mixed-phase nature of all LEM samples having a hexagonal unit cell structure with a less detectable impurity (Eu2O3) ceramics. The patterns are zanalyzed in detail with structural distortion and strain in LEM manganites ceramics. Dielectric constant and modulus are found to increase with increasing Eu concentration. The samples LEM-0.10 shows the negative capacitance at low frequency and temperature, respectively.

Adverse Effect of Europium Doping on Magneto-Optical Properties of Cr2O3

The article describes in detail the effect of doping Europium (Eu) on magnetic and optical properties of Cr2O3. Undoped and Eu (1–5 mol%) doped Cr2O3 samples were synthesized using solid state synthesis method. The structural, magnetic and optical properties of undoped and Europium (Eu) doped chromium oxide powder were studied by X-ray diffractometer (XRD), vibrating sample magnetometer (VSM) and photoluminescence (PL) measurements. The X-ray diffraction pattern confirms the polycrystalline nature of undoped and Europium (Eu) doped chromium oxide powder. The magnetic measurements revealed decline in magnetism with increasing Eu concentration. With increasing Eu concentration, the visible luminescence of Cr2O3 improved. The study highlighted that Eu as a dopant is not suitable for improving the magnetic properties of Cr2O3.

Structural, Optical and Electrical Properties of Eu-doped CuS Nanoparticles Synthesized Through the Aqueous Route

Eu-doped CuS nanoparticles stabilized by L-cysteine were synthesized by a low-temperature soft aqueous route. X-Ray Diffraction (XRD) patterns of the synthesized products reveal the formation of the hexagonal structure of covellite CuS. Scanning Electron Microscopy (SEM) images depict that the as-prepared nanoparticles exhibit relatively sphere like shaped morphology. Transmission Electron Microscopy (TEM) analyses show that the average size of the nanoparticles was found to be reduced with increasing the Eu concentration. UV-Visible optical absorption measurements reveal that the optical band gap is increased with increasing the Eu concentration, showing the presence of a blue shift due to quantum size effects. Impedance spectra were well modelled by introducing an electrical equivalent circuit. The electrical conductivity was found to be increased with increasing the Eu concentration. The temperature dependence of the DC conductivity confirmed the semiconducting nature of the as-prepared nanoparticles and was found to obey the Arrhenius law with two activation energies. The frequency dependence of the AC conductivity has been analyzed by Jonscher’s power law suggesting the non-overlapping small polaron tunneling (NSPT) type of conduction. The polaron hopping energy was found to be increased with increasing the Eu concentration. The dielectric constant of the as-synthesized nanoparticles was found to be decreased with the increase in Eu concentration. The dielectric loss tangent was found to be decreased and then increased at higher frequencies with increasing the Eu concentration.

Tuning the microstructural, optical and superexchange interactions with rare earth Eu doping in nickel ferrite nanoparticles

A methodical study on structural, magnetic and optical properties of Eu doped NiFe2O4 nanoparticles with generic composition NiEuxFe2-xO4 (x = 0.00, 0.02, 0.04 and 0.06), synthesized via co-precipitation technique has been reported in this article. The fabrication of single phase ferrite nanoparticles was verified using X-ray powder diffractograms. The analysis of W–H plots revealed the presence tensile strain in the samples along with an average crystallite size of 20 ± 4 nm. The existence lowering of cubic symmetry at octahedral sublattices was detected by vibrational Raman spectra recorded at 300 K. The values of indirect optical band gap were noted in the range of 1.76 ± 0.02 eV. The hysteresis loops at room temperature supported the paramagnetic character of Eu3+ ions in spinel structure. The evidence of reduced A-O-B superexchange interaction along with reduction of saturation magnetization was also found for higher Eu content nanoparticles at 300 K. The coercivity was observed to increase at 5 K. The blocking temperature and thermo-magnetic irreversibility was reduced with increasing Eu concentration.

Observation of single optical site of Eu and Mg codoped GaN grown by NH3-source molecular beam epitaxy

Eu-doped GaN (GaN:Eu) is a promising solid-state material for quantum information devices owing to its ideal quantum levels. However, a decrease of Eu concentration and the unification of optical sites are required for these devices to access an Eu ion. In this article, the effect of Eu concentration on the optical properties of Mg-codoped GaN:Eu was evaluated. The photoluminescence intensity from Eu ions increased linearly with increasing Eu concentration up to 1 × 1019 cm−3, beyond which the intensity saturated. This resulted from the increase of the sharp luminescence line at 620.5 nm (site A), which has a large excitation cross section, with increasing Eu concentration in the range of low Eu concentrations; an excess Eu concentration leads to the formation of other types of optical sites with a low transfer efficiency or inactive sites. For a low Eu concentration of 3 × 1018 cm−3, all optical sites except a specific optical site corresponding to site A disappeared, and the unification of optical sites was suggested. This result is expected to be valuable to realize quantum information devices.

Effect of Eu doping on the near band edge emission of Eu doped ZnO thin films after high temperature annealing

Abstract We studied the effect of europium (Eu) doping on the near band edge emission of ZnO thin films, fabricated by sputtering and high temperatures annealing. The doping concentration of Eu in the ZnO films was varied from 0.01 to 0.62 at.%. Photoluminescence (PL) spectra showed that the films ultra-violet (UV) emission was enhanced very much by high temperature treatment and was stronger for the Eu doped ZnO than that for the un-doped ZnO films after 1100 °C annealing. X-ray diffraction showed the films had hexagonal wurtzite structure, the width of the ZnO (002) plane diffraction peak was sensitive to the anneal temperature and also to the Eu doping concentration, and Zn silicates had formed after the 1100 °C annealing. Scanning electron microscopy showed that the surface morphology of the films became more uneven with increasing Eu concentration. The PL decay spectra inferred that the lifetime of the UV PL was correlated with the size of ZnO nanocrystals in the films. The results support that the intensity of the UV PL is primarily influenced by the crystalline perfection of the films which is also influenced by the Eu doping concentration.

Спектральные и структурные характеристики вольфраматов (Lu-=SUB=-1-x-=/SUB=-Eu-=SUB=-x-=/SUB=-)-=SUB=-2-=/SUB=-(WO-=SUB=-4-=/SUB=-)-=SUB=-3-=/SUB=-

Investigated are the structure, luminescence, and IR absorption spectra of (Lu1−xEux)2(WO4)3 solid solutions in a wide range of Eu concentrations (0 ≤ x ≤ 1). A sequential replacement of two types of crystalline phases occurs with an increase in Eu concentration. The orthorhombic phase (Pbcn space group) of tungstate solid solutions is observed at 0 ≤ x < 0.5. A monoclinic phase (C2/c space group) arises along with the orthorhombic one in the range of 0.5 ≤ x ≤ 0.8, while at x > 0.8, the solid solution has a monoclinic structure. The correspondence between the structure and spectral characteristics of these compounds is established. A change in the structural state results in a change in luminescence spectra, as well as in the spectra of luminescence excitation of tungstates. The isotherm of water adsorption by the tungstate samples and its effect on their spectral and structural characteristics are studied in view of the wetting ability of (Lu1−xEux)2(WO4)3 solid solutions. It is established that the maximum luminescence under the resonant excitation of Eu3+ ions is observed in the samples with a monoclinic C2/c structure at x ~0.9.

Functionalizing window coatings with luminescence centers by combinatorial sputtering of scatter-free amorphous SiAlON:Eu2+ thin film composition libraries

SiAlON window coatings are applied on an industrial scale to achieve e.g. scratch-resistance and anti-reflection. Doping these SiAlONs with rare-earths adds luminescent functionality, which could be applied in photovoltaics. By using a combinatorial reactive sputtering approach, an amorphous thin film composition library with a Si:Al ratio from 0.062:1 to 3.375:1 and a Eu doping from 4.8 at% to 26 at% is created. This library uniquely combines high absorption, strong emission and absence of light scattering. By combining position-dependent EDX measurements with transmission and emission spectra, properties like the index of refraction, absorption strength, emission wavelength and decay times of the library can directly be related to the composition. Throughout the library, an index of refraction of 1.63±0.03 is observed, typical for a film with low nitrogen content. The library also shows a large absorption coefficient of 1294±8cm−1at.%−1. Laser-excited emission spectra show that the library has a strong redshift from 500 nm to 550 nm with increasing Al concentration. An increase in Eu concentration also causes a shift of the emission to red. Decay spectra show that a high degree of Si greatly improves the luminescence intensity. These functionalized SiAlON coatings can be of great interest for transparent and scatter-free luminescent solar concentrators applied as windows.

Self-Organized Eu-Doped GaN Nanocolumn Light-Emitting Diode Grown by RF-Molecular-Beam Epitaxy

High-concentration doping of Eu ions working as luminescent centers in GaN is required to improve light output of optical devices. GaN nanocolumns can be used to achieve high crystallinity in high-concentration Eu-doped GaN (GaN:Eu). In this study, optical properties of a GaN:Eu nanocolumn grown by RF-plasma-assisted molecular-beam epitaxy (RF-MBE) are investigated and GaN:Eu nanocolumn light-emitting diodes (LEDs) are demonstrated. Suppression of yellow luminescence and concentration quenching of PL intensity are observed at RT for GaN:Eu nanocolumns. When the effect of Eu concentration on optical properties is analyzed using rate equation, an increase in the Eu concentration is observed to affect 5D0 lifetime corresponding to back transfer, and not the effective cross-section corresponding to transfer efficiency. Based on these results, GaN:Eu nanocolumn LEDs are fabricated on an n-type (111) Si substrate. Clear rectification characteristics and sharp red luminescence are observed. The light output increases with increasing Eu concentration up to a concentration of 6 × 1020 cm−3. These results suggested that GaN:Eu nanocolumns provide feasible crystal to realize novel optical devices.