Er Segregation Research Articles

Substitution potential of La/Ce/Er for high-cost Sc in rare-earth Al alloys: A comprehensive first-principles study

Al–Sc alloys have high strength, plasticity, and corrosion resistance, making them ideal lightweight materials for the aerospace and automotive industries. However, the practical application of these alloys is constrained by the high cost of Sc. We investigate the substitution potential of lower-cost rare-earth elements X (X = La, Ce and Er) for the expensive Sc in Al–Sc alloys through first-principles calculations. Assessing substitution formation energy, substitutional segregation, and their impact on (001), (110), and (111) γ-Al/γ′-Al3Sc interfaces, results highlight Er as the most promising candidate among the three, thermodynamically replacing Sc in Al3Sc precipitates. Er atoms selectively segregate to γ-Al/γ′-Al3Sc interfaces, enhancing stability by reducing interface energies. The morphology of precipitates undergoes a transition from a truncated cuboctahedron to an {111}-faceted octahedron. Increased Er segregation further bolsters interfacial fracture strength, attributed to segregation-induced charge accumulation. Our work could offer reference for the design of rare-earth Al alloys with low-cost and high-performance.

Effect of Er and Si co-microalloying on mechanical properties and microstructures of AlCuMg alloys

The effect of Er and Si on the evolution of precipitates in Al–Cu–Mg alloys during elevated temperature exposure was investigated. The Er segregation in θ′-Al2Cu precipitates and Si/Mg co-segregation at the interfaces of θ'/Al matrix are experimentally observed in Al–Cu–Mg–Si–Er alloy, which finally contributes to the heat resistance of the Al–Cu–Mg–Si–Er alloy. Si enhances formation of the Q″ phases as nucleation sites for the θ′ phases, resulting in a refined distribution of θ′ phases. Al–Cu–Mg alloy with high strength as well as high thermal stability is obtained by co-adding Er and Si. The high-temperature yield strength (YS) of Al–Cu–Mg–Si–Er alloy at 225 °C are increased by 37 MPa compared with that of Al–Cu–Mg alloy. Simultaneously, the addition of Er significantly increases the elongation of Al–Cu–Mg–Si–Er alloy.

Processing-dependent stabilization of a dissimilar rare-earth boride in high-entropy (Ti0.2Zr0.2Hf0.2Ta0.2Er0.2)B2 with enhanced hardness and grain boundary segregation

This study demonstrates that 20% of a rare-earth (RE) diboride (ErB2) can be stabilized in a high-entropy transition metal (TM) diboride, despite the dissimilar chemical properties of RE and TM elements and large differences in lattice parameters of ErB2 and typical TMB2. However, the phase formation depends on the fabrication route, which is a noteworthy observation. Specifically, single-phase (Ti0.2Zr0.2Hf0.2Ta0.2Er0.2)B2 is synthesized via reactive spark plasma sintering (SPS) using elemental boron and metal elements. In contract, a specimen made by borocarbothermal reduction of binary oxides and SPS possess significant amounts of two Er-rich secondary phases. Notably, the RE addition in high-entropy TM diboride leads to improved hardness. Aberration-corrected scanning transmission electron microscopy (AC STEM) and energy-dispersive X-ray spectroscopy (EDS) elemental analyses further reveal significant Er segregation at grain boundaries. This work suggests that high-entropy ceramics can have significant solubilities of dissimilar components that may enable new, tunable, and improved properties.

Effect of Heat Treatment on Microstructural Evolution and Microhardness Change of Al-5Zn-0.03In-1Er Alloy

Adding an appropriate amount of Er element to Al-Zn-In alloys can improve the electrochemical performance of Al alloys; it is convenient to study the electrochemical behavior of the alloy in the rest of our work. However, Er segregation in solid solutions which reduced the comprehensive properties of alloys was difficult to reduce and there was no report on the homogenization of Al-Zn-In alloys. We found that the ultra-high temperature treatment (UHTT) can obviously reduce Er segregation. To explore the better homogenization treatment and the microstructure evolution of Al-5Zn-0.03In-1Er alloy after UHTT, we carried out a series of heat treatments on the alloy and characterized the microstructure of the alloy by optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy spectrum analysis (EDS) and transmission electron microscopy (TEM). The results showed that the main element Er of the Al-Zn-In-Er was largely enriched in grain boundaries after UHTT; the distribution Zn and In was almost unchanged. The as-cast Al-Zn-In-Er alloy consisted mainly of α(Al) solid solution and Al3Er phase. As the temperature of UHTT increased and the treatment time prolonged, the precipitated phase dissolved into the matrix, and there were dispersed Al3Er particles in the crystal. The proper UHTT for reducing the interdendritic segregation of the alloy was 615 °C × 32 h, which was properly consistent with the results of the evolution of the statistical amount of interdendritic phase, the line scanning analysis and the microhardness. Moreover, the microhardness of the alloy after treatment of 615 °C × 32 h was obviously higher than that of the as-cast alloy because of the anchoring effect of Al3Er nanoparticles on the movement of dislocations.

Silicon shallow doping by erbium and oxygen recoils implantation

Abstract In order to get shallow high doping of Si with optically active complexes ErOn, Er followed by O recoils implantation was realized by means of subsequent Ar+ 250–290 keV implantation with doses 2×1015–1×1016 cm–2 through 50-nm deposited films of Er and then SiO2, accordingly. High Er concentration up to 5×1020 cm−3 to the depth of 10 nm was obtained after implantation. However, about a half of the Er implanted atoms become part of surface SiO2 during post-implantation annealing at 950 °С for 1 h in the N2 ambient under a SiO2 cap. The mechanism of Er segregation into the cap oxide following the moving amorphous–crystalline interface during recrystallization was rejected by the transmission electron microscopy (TEM) analysis. Instead, the other mechanism of immobile Er atoms and redistribution of recoil-implanted O atoms toward cap oxide was proposed. It explains the observed formation of two Er containing phases: Er–Si–O phase with a high O content adjacent to the cap oxide and deeper O depleted Er–Si phase. The correction of heat treatments is proposed in order to avoid the above-mentioned problems.

Sintering and open die forging process for P/M titanium alloy with additions of trace amount of erbium

Er powder with a very large particle size was added to Ti metal and Ti–6Al–4V alloy to achieve a supersolidus liquid sintering effect. However, instead of promoting sintering and homogenisation, very big worm-like voids were created by a substantial Er–Ti liquid phase. Such voids were surrounded by Er segregation and made tensile testing of a Ti–Er alloy impossible. An open die forging process was then employed to diminish these pores and homogenise the Er distribution. Fine Er spots or acicular textures were found in the matrix, but some Er segregation still persisted. The material is weakened by segregation. Good mechanical properties are obtained when the testpieces have reduced levels of Er segregation. Further work will be focused on the homogenisation of Er.

Influence of MgO codoping on Er concentration in congruent LiNbO3 crystal: Mg threshold concentration effect

Congruent Er:Mg:LiNbO3 crystals were grown by the Czochralski method from the melts containing fixed 0.5 mol% Er2O3 while varied MgO content ranged from 0.0 to 8.0 mol%. The Mg and Er contents in the crystals were determined by neutron activation analysis. In the presence of Er codopant, the Mg threshold concentration with respect to optical damage is determined from the measured OH absorption spectra. The results show that the Er codopant has less effect on both the Mg threshold concentration and Mg segregation coefficient, which is within 1.13–1.23 as the Mg concentration is below the threshold while within 0.88–0.98 when above the threshold, consistent with the only MgO doping case. On the other hand, the practical Er concentration in the crystal is closely related to the Mg content and shows definite Mg threshold effect. Below the threshold, the Er concentration decreases linearly with the increased Mg concentration in the crystal; above the threshold, the decrease is more remarkable and follows another linear function. The Mg concentration effect on the Er segregation coefficient is discussed from the viewpoint of the Mg doping effect on the solubility of Er ions in the crystal.

Redistribution of Er implanted into Si(1 0 0): Correlation with implantation induced damage

The redistribution of Er in Si is studied by annealing samples of Si implanted with 200 keV Er at doses 5 × 10 14 and 3.2 × 10 15 ions/cm 2, respectively. Er profiles are measured by secondary ion mass spectrometry and implantation induced damage by cross-sectional transmission electron microscopy. A continuous amorphous layer is formed extending from surface to the end of range for the as-implanted high dose sample which recrystallizes by solid phase epitaxial process with substantial [1 1 1] twins and {1 1 1} stacking faults near the surface region after annealing at 900 °C for 30 min. The high dose sample after annealing is characterised by Er trapping of maximum concentration of 8 × 10 19/cm 3 at the heavily twinned recrystallized region with a decreased concentration at the surface. On the other hand the low dose sample after annealing shows Er segregation of concentrations up to 3 × 10 20/cm 3 at the surface.

High concentration erbium doping of silicon-rich SiO 2 thin films on silicon

In this work, high concentration erbium doping in silicon-rich SiO 2 thin films is demonstrated. Si plus Er dual-implanted thermal SiO 2 thin films on Si substrates have been fabricated by using a new method, the metal vapor vacuum arc ion source implantation with relatively low ion energy, strong flux and very high dose. X-Ray photoelectron spectroscopy measurement shows that very high Er concentrations on the surfaces of the samples, corresponding to ∼10 at.% or the doping level of ∼10 21 atoms cm −3, are achieved. This value is much higher than that obtained by using other fabrication methods such as the high-energy ion implantation and molecular beam epitaxy. Reflective high-energy electron diffraction, atomic force microscopy and cross-section high-resolution transmission electron microscopy observations show that the excess Si atoms in SiO 2 matrix accumulate to form Si clusters and then crystallize gradually into Si nanoparticles embedded in SiO 2 films during dual-ion implantation followed by rapid thermal annealing. Er segregation and precipitates are not formed. Photoluminescence at the wavelength of 1.54 μm exhibits very weak temperature dependence due to the introduction of Si nanocrystals into the SiO 2 matrix. The 1.54-μm light emission signals from annealed samples decrease by less than a factor of 2 when the measuring temperature increases from 77 K to room temperature.

Electrical properties of silicon layers implanted with erbium and oxygen ions in a wide dose range and thermally treated in different temperature conditions

The electrical properties of silicon implanted with Er and O ions in a wide dose range have been studied. The dependence of electron mobility on the concentration of electrically active centers is determined for Si:Er layers with Er concentrations in the range of 9×1015–8×1016 cm−3. Sharp bends related to specific features of Er segregation in solid-phase epitaxial recrystallization are observed in the concentration profiles of electrically active centers, n(x), and Er atoms, C(x), at Er ion implantation doses exceeding the amorphization threshold. The n(x) and C(x) profiles virtually coincide near the surface. A linear rise in the maximum concentration of electrically active centers at approximately constant effective coefficient of their activation, k, is observed at Er implantation doses exceeding the amorphization threshold. At an Er concentration higher than 7×1019 cm−3, the concentration of electrically active centers levels off and k decreases.

Mutants affecting the structure of the cortical endoplasmic reticulum in Saccharomyces cerevisiae.

We find that the peripheral ER in Saccharomyces cerevisiae forms a dynamic network of interconnecting membrane tubules throughout the cell cycle, similar to the ER in higher eukaryotes. Maintenance of this network does not require microtubule or actin filaments, but its dynamic behavior is largely dependent on the actin cytoskeleton. We isolated three conditional mutants that disrupt peripheral ER structure. One has a mutation in a component of the COPI coat complex, which is required for vesicle budding. This mutant has a partial defect in ER segregation into daughter cells and disorganized ER in mother cells. A similar phenotype was found in other mutants with defects in vesicular trafficking between ER and Golgi complex, but not in mutants blocked at later steps in the secretory pathway. The other two mutants found in the screen have defects in the signal recognition particle (SRP) receptor. This receptor, along with SRP, targets ribosome-nascent chain complexes to the ER membrane for protein translocation. A conditional mutation in SRP also disrupts ER structure, but other mutants with translocation defects do not. We also demonstrate that, both in wild-type and mutant cells, the ER and mitochondria partially coalign, and that mutations that disrupt ER structure also affect mitochondrial structure. Our data suggest that both trafficking between the ER and Golgi complex and ribosome targeting are important for maintaining ER structure, and that proper ER structure may be required to maintain mitochondrial structure.

X-ray reflectivity measurement of δ-doped erbium profile in silicon molecular-beam epitaxial layer

Synchrotron radiation x-ray reflectivity measurement is used to study the concentration profile of a delta-doped Er layer in Si epitaxial film grown by molecular-beam epitaxy. The oscillation of the reflectivity amplitude as a function of reflection angle is observed in the experiment. By doing a theoretical simulation, the concentration profile of Er atoms could be derived. It is shown that the originally grown delta-doped Er layer changes into an exponentially decayed function due to the Er segregation. The temperature dependence of the 1/e decay length indicates that the segregation is a kinetically limited process. The activation energy is determined to be 0.044 +/- 0.005 eV. [S0163-1829(99)11515-7].

Incorporation and optical activation of erbium in silicon using molecular beam epitaxy

Erbium is incorporated in crystalline silicon during molecular beam epitaxy on Si(100) at 600 °C, either in vacuum (6×10−11 mbar) or in an O2 ambient (4×10−10 mbar). Strong Er segregation takes place during growth in vacuum, and only 23% of the total deposited Er is incorporated in the epitaxial layer. Films grown in an O2 ambient show no Er segregation, and an Er concentration of 1.5×1019 Er/cm3 is incorporated in the crystal. The O content is 4×1019 O/cm3. Photoluminescence spectra taken at 10 K show the characteristic intra-4f luminescence of Er3+ at 1.54 μm for both samples, grown with and without O2. Differences found in the spectral shape indicate a difference in the local environment (presumably O coordination) of Er for the two cases. The O codoped film shows a 7 times higher Er luminescence peak intensity than the film grown without O. This is due to the higher incorporated Er concentration as well as an increased luminescence efficiency (lifetime without O: 0.33 ms, with O: 1.81 ms). The Er excitation efficiency is lower in the O codoped film than in the O-undoped film, which is attributed to the lower minority carrier lifetime in the O-doped material. Thermal annealing of the O codoped film at 1000 °C increases the excitation efficiency and hence the Er luminescence intensity.

Segregation and trapping of erbium during silicon molecular beam epitaxy

Erbium surface segregation is observed during growth of Er-doped Si by molecular beam epitaxy on Si(100) at 600 °C. Once a critical Er surface areal density of 2×1014 Er/cm2 is reached, enhanced Er trapping is observed, possibly due to the formation of silicide precipitates. Er segregation on Si(100) is fully avoided when growth is performed in an oxygen background pressure of ∼10−10 mbar, due to the formation of Er-O complexes. No Er segregation is observed on Si(111), which is attributed to the formation of epitaxial Er3Si5 precipitates.