Composition Of Solid Solution Research Articles

Dissolution and solubility of the calcium-nickel carbonate solid solutions [(Ca1−xNix)CO3] at 25 °C

A series of the calcium-nickel carbonate solid solutions [(Ca1−xNix)CO3] were synthesized and their dissolution in N2-degassed water (NDW) and CO2-saturated water (CSW) at 25 °C was experimentally investigated. During dissolution of the synthetic solids (Ni-bearing calcite, amorphous Ca-bearing NiCO3 and their mixtures), the Ni-calcite and the Ca-NiCO3 dissolved first followed by the formation of the Ni-bearing aragonite-structure phases. After 240–300 days of dissolution in NDW, the water solutions achieved the stable Ca and Ni concentrations of 0.592–0.665 and 0.073–0.290 mmol/L for the solids with lower Ni/(Ca + Ni) mol ratios (XNi), or 0.608–0.721 and 0.273–0.430 mmol/L for the solids with higher XNi, respectively. After 240–300 days of dissolution in CSW, the water solutions achieved the stable Ca and Ni concentrations of 1.094–3.738 and 0.831–4.300 mmol/L, respectively. For dissolution in NDW and CSW, the mean values of log IAP (Ion activity products) in the final stable state (≈ log Ksp, Solubility product constants) were determined to be − 8.65 ± 0.04 and − 8.16 ± 0.11 for calcite [CaCO3], respectively; − 8.50 ± 0.02 and − 7.69 ± 0.03 for the synthetical nickel carbonates [NiCO3], respectively. In respect to the bulk composition of the (Ca1−xNix)CO3 solid solutions, the final log IAP showed the highest value when XNi = 0.10–0.30. Mostly, the mean values of log IAP increased with the increasing XNi in respect to the Ni-calcite, the Ni-aragonite and the amorphous Ca-Ni carbonate. The plotting of the experimental data on the Lippmann diagram for the (Ca1−xNix)CO3 solid solution using the predicted Guggenheim parameters of a0 = 2.14 and a1 = − 0.128 from a miscibility gap of XNi = 0.238 to 0.690 indicated that the solids dissolved incongruently and the final Ca and Ni concentrations in the water solutions were simultaneously limited by the minimum stoichiometric saturation curves for the Ni-calcite, Ni-aragonite and the amorphous Ca-Ni carbonate. During dissolution in NDW, the Ni2+ preferred to dissolve into the water solution and Ca2+ preferred to remain in the solid, while during dissolution in CSW for the solids with higher XNi, the Ca2+ preferred to dissolve into the water solution and Ni2+ preferred to remain in the solid. These findings provide valuable insights into understanding the mechanisms governing Ni geochemical cycle in natural environments.

Phase Formation Behavior and Thermoelectric Transport Properties of Solid Solution Composition Between SnTe and InTe

Phase Formation Behavior and Thermoelectric Transport Properties of Solid Solution Composition Between SnTe and InTe

Indium-Iron Oxide Nanosized Solid Solutions as Photocatalysts for the Degradation of Pollutants under Visible Radiation.

A series of solid solutions of indium and iron oxides with different In/Fe ratios (InxFeyO3, with x + y = 2) were synthesized in the form of nanoparticles (diameter of ca. 30-40 nm) with the purpose of generating enhanced photocatalysts with an intermediate band gap compared to those of the monometallic oxides, In2O3 and Fe2O3. The materials were prepared by co-precipitation from an aqueous solution of iron and indium nitrates and extensively characterized with a combination of techniques. XRD analysis proved the formation of the desired InxFeyO3 solid solutions for Fe content in the range 5-25 mol%. UV-Vis absorption analysis showed that the substitution of In with Fe in the crystalline structure led to the anticipated gradual decrease of the band gap values compared to In2O3. The obtained semiconductors were tested as photocatalysts for the degradation of model organic pollutants (phenol and methylene blue) in water. Among the InxFeyO3 solid solutions, In1.7Fe0.3O3 displayed the highest photocatalytic activity in the degradation of the selected probe molecules under UV and visible radiation. Remarkably, In1.7Fe0.3O3 showed a significantly enhanced activity under visible light compared to monometallic indium oxide and iron oxide, and to the benchmark TiO2 P25. This demonstrates that our strategy consisting in engineering the band gap by tuning the composition of InxFeyO3 solid solutions was successful in improving the photocatalytic performance under visible light. Additionally, In1.7Fe0.3O3 fully retained its photocatalytic activity upon reuse in four consecutive cycles.

Solid-solution Er:(Sc,Y)2O3 transparent ceramics: Optical spectroscopy, inhomogeneous line broadening, C3i sites and mid-infrared laser operation

Rare-earth-doped transparent sesquioxide laser ceramics enable engineering of their gain bandwidths via solid-solution compositions exhibiting a strong inhomogeneous spectral line broadening. We report on a detailed spectroscopic study and the first mid-infrared laser operation of Erbium-doped yttria-scandia, (ScxY1−x)2O3, ceramics fabricated by vacuum sintering at 1750 °C from laser-ablated nanoparticles. The effect of the Sc fraction on the spectral and kinetic properties of Er3+ emission around 2.8 μm owing to the 4I11/2 → 4I13/2 is revealed. The inhomogeneous spectral line broadening leading to merging of individual Stark sub-levels of Er3+ multiplets is evidenced by low-temperature spectroscopy. An original method of quantifying the distribution of dopant Er3+ ions over C2 and C3i symmetry sites in the cubic bixbyite structure is suggested based on the transition probabilities derived by the Judd-Ofelt theory. In the parent Er:Y2O3 ceramic, the Er3+ ions nearly follow the ideal distribution with 3/4 of ions residing in C2 sites, and Sc addition skews it in favor of C3i sites. A continuous-wave Er:(Sc,Y)2O3 ceramic laser generated 312 mW at 2716 nm with a slope efficiency of 18.6 % and a laser threshold of 128 mW.

Establishing Composition of Solid Solution Based on Single Crystal and Powder X-ray Measurement: The Case of Halogenated Bismuth(III) Complexes with Acetophenone-4-methyl-3-thiosemicarbazone

New bismuth (III) complexes with acetophenone-4-methyl-3-thiosemicarbazone (L) and halogens (Cl and Br) in both bridging and terminal positions have been synthesized and structurally characterized using single-crystal X-ray diffraction. The pure complexes (Cl or Br) were found to be highly isostructural, which motivated our attempts to create solid solutions of these complexes. A series of such compounds was prepared using various procedures and stoichiometries. A method for determining the mutual concentrations of different halogens, based on the positions of selected peaks in powder diffraction patterns, was tested and compared with other methods.

Electrical and thermal transport properties of Cr2Se3-Cr2Te3 solid-solution alloy system and estimation of optimal thermoelectric properties

Cr2Se3 is a layered narrow-bandgap semiconductor with a low lattice thermal conductivity of ∼1 W/mK, which can be considered as a potential thermoelectric material. A solid-solution alloy system with Cr2Te3 can be designed to manipulate the electrical and thermal transport properties. In this study, a series of Cr2Se3-Cr2Te3 solid-solution alloys (Cr2(Se1-xTex)3, x = 0, 0.33, 0.5, 0.67, 0.83, and 1) were synthesized, and their electrical and thermal transport properties were investigated. Regarding the electrical transport properties, the power factor (∼0.35 mW/mK2) of Cr2Se3 gradually and significantly decreased as the Te content (x) increased owing to the significant decrease in the Seebeck coefficient that resulted from the large increase in the carrier concentration. Regarding the thermal transport properties, the total thermal conductivity increased with x as a result of the large increase in the electrical conductivity, despite the continuous decrease in the lattice thermal conductivity. Consequently, the thermoelectric figure of merit (zT ∼ 0.20) of Cr2Se3 gradually and significantly decreased to 0.009 for Cr2Te3 at 700 K; thus, no enhancement of zT was observed from the experimental results of simple solid-solution alloying. On the other hand, the thermoelectric quality factors of the solid-solution compositions for x = 0.33–0.83 were found to be enhanced compared to that of the Cr2Se3 sample, implying that zT could be further enhanced by optimizing the carrier concentration. Indeed, enhanced zT values were estimated based on a single parabolic band model for the solid-solution compositions with x = 0.33–0.83 if the carrier concentration was optimized to ∼1019 cm−3, which was found to be owing to the increased nondegenerate and weighted mobility (inferring weaker carrier–phonon interaction). Therefore, it is suggested that the solid-solution alloying approach could provide a feasible strategy to enhance the thermoelectric performance by reducing carrier-phonon interaction when further combined with carrier concentration optimization.

Data-Driven Material Exploration of High Conductive Fluorides By Multi-Element Substitution

Barium fluoride (BaF2) has a fluorite-type structure and is attracting high attention as a solid electrolyte material for fluoride ion batteries that can be used under high voltage. Previous research has reported that the ionic conductivity increases by 4 to 5 orders of magnitude by partially replacing Ba in BaF2 with La. This indicates that elemental substitution is effective in improving the ionic conductivity of BaF2. However, single element substitution only explore much limited experimental space in elements, so that it should be difficult to discover innovative conductive compositions. By replacing various elements at the same time, the experimental space can be largely expanded and the possibility of finding the optimal composition increases. But, the combination numbers of multi-element substituted compositions are much over 10000, and exhaustive exploration of them is unrealistic. Therefore, we aimed to efficiently search for multi-element substitution compositions with high conductivity by creating a material-conductivity correlated exploring system under data-driven approach using large number of fluoride material database. The purpose of this research was to discover solid solution compositions in the multi-element substituted fluorides and understanding of the relationship between substitutional elements and solid solution formation.Approximately 20 types of multi-element substitution composition candidates were initially picked up using the D-optimal design (Dopt). The target compositions were synthesized to collect their XRD data. Next, we extracted the "number of peaks" from the XRD data as a feature values to express the degree of solid solution in the sample. Furthermore, we made a regression model with the element types and addition ratios as explanatory variables and the "number of peaks" as the objective variable. Using the regression model, approximately 20 candidate were predicted to form solid solution, in which we called as data-driven design of experiments (DOE) approach. Finally, the materials were actually prepared according to the proposal in DOE. The identification results were projected using the principal component analysis (PCA) to draw the material space.The obtained material space shows the number of peaks in the samples prepared using DOE decreased compared to those using Dopt. In detail, the Dopt-derived sample had 41.83 peaks, while the DOE-derived sample had 19.65 peaks on average. This result indicates that we were able to efficiently find preferable compositions that are advantageous for solid solution formation by using the data-driven method.In the presentation, we will also report the high-throughput composition exploration, their conductivities, and also development of virtual X-ray diffraction simulation system for over 10,000 kinds of multi-substituted composition of the fluorides. Acknowledgement s This research was partially supported by Knowledge Hub Aichi, the GIMRT Program of the Institute for Materials Research, Tohoku University (Proposal No. 202303-CRKKE-0048).

A Combined Theoretical and Experimental Raman Scattering Study of BaZrS3-BaHfS3 Solid Solutions.

Ba(Zr,Hf)S3 solid solutions are proposed for photovoltaic applications and a fast non-destructive measurement of the composition of these solutions and the identification of any possible secondary phases is a prerequisite for understanding their opto-electronic properties. Previously multi-wavelength Raman spectroscopy has been used for such purposes in other chalcogenide solution series. Here we calculate the non-resonant one-phonon Raman spectra of pure BaHfS3 and BaZrS3, which show only subtle differences between them, since the most prominent modes are dominated by the sulfur atoms and the change in mass of going from Hf to Zr is balanced by a near equal and opposite change in the bonding. To test this experimentally, a solution series of BaZr1-xHfxS3 (0≤x≤1) powders was synthesised and free of a secondary phase, HfS3 identified by 633 nm excitation Raman spectroscopy. The veracity of the synthesis method was confirmed by comparing X-ray diffractograms and optical absorption spectra of the BaZr0.5Hf0.5S3 alloy to a 50 : 50 mixture of the pure ternary compounds. Experimental non-resonant Raman measurements on the alloy powders confirm that only slight variations in the spectra are visible, making an alloy composition determination difficult. However, exciting the alloys resonantly, leads to the appearance of new two-phonon modes in the Raman spectrum, which change significantly across the alloy series. We consequently suggest that a rapid alloy composition measurement can be made unambiguously by measuring the ratio of the intensities of the 825 cm-1 and 625 cm-1 Raman features.

Influence mechanism of ZnCdS solid solution composition regulation on its energy band and photocatalytic hydrogen performance

The regulation of the band structure is crucial for the improvement of the photocatalytic performance, but the relationship between the composition of solid solution catalyst and their band structure is still unclear. Herein, the solid solution catalysts ZnxCd1-xS (1 > x > 0) were designed and synthesized using a handy solid-phase thermal decomposition strategy. It is interesting that the band structure and photocatalytic hydrogen production (PHP) performance of the obtained solid solution catalyst can be cleverly regulated by controlling the atomic ratio of the solid solution. Among the obtained series of ZnxCd1-xS solid solution catalysts, the optimal solid solution catalysts Zn0.5Cd0.5S exhibits the best PHP activity and favorable cycle stability: the corresponding PHP rate is 41211.2 μmol·h−1·g−1 and the QE value is 7.7 % at 400 nm. The outstanding photocatalytic hydrogen production performance is the result of significantly narrowing the band gap of sulfide solid solution. Additionally, the effective separation and transfer rate of photogenerated carrier has also been improved effectively. The construction of bimetallic sulfide solid solution photocatalyst via an ingenious solid-state thermal decomposition strategy in this work provided a new idea for improving the photocatalytic performance of bimetallic catalysts.

Powstawanie polifazowej asamblaży minerałów z grupy platynowców w masywie dunitowo-szonkinitowym Inagli w Aldan Shield na platformie syberyjskiej

The Inagli massif is a concentric-zonal ring massif consisting of a dunite core bordered by a sequential series of peridotites, pyroxenites and shonkinites. In dunites, there are densely disseminated accumulations of chromspinelides, as well as schlieren and veined particles of massive chromitites, to which polyphase growths of platinum-group minerals (PGM) are confined. The Inagli intrusive, like the well-known Konder massif, belongs to an independent "Aldan" type of platinum-bearing deposits. The Aldan type of ring intrusions is a platform analogue of the "Ural-Alaskan" zonal dunite-gabbro massifs of orogenic regions. In placers, dunites and chromitites of the Inagli massif, PGM are mainly represented by isoferroplatinum (Pt3Fe) with an admixture of iridium up to 8 wt %. In isoferroplatinum, symplektitic iridium particles and small inclusions of osmium, laurite, ehrlichmanite, malanite, as well as other sulfides and arsenides of platinum-group elements (PGE) are often observed. The bulk composition of such polymineral aggregates can be calculated based on the volume ratios and chemical composition of individual phases. The results obtained in this way show that the compositions of the initial polycomponent solid solutions vary from Pt-Ir-Fe to Ir-Os-Ru-Rh-Pt-Pd-Fe alloys. Polycomponent homogeneous solid solutions, which composition gradually changes from Ru-Rh-Ir-Os minerals to Fe-Pt alloys, are known in the Witwatersrand placers. A similar series of solid solutions of PGE is identified in the placers of the Guli massif on the Siberian platform. Unlike the placers of the Witwatersrand and Guli massif, where PGM are mainly represented by Os-Ir alloys, Inagli minerals have mainly a Pt-Ir-Fe composition with a low proportion of Os. The structures of most natural polyphase PGM aggregates are similar to those of artificial alloys, therefore, the former are also products of crystallization of multicomponent metal melts and their subsequent solid-phase transformations. The limits of solubility between PGE differ significantly, therefore, depending on the initial composition of metal alloys, both polycomponent solid solutions and polymineral aggregates can be formed. Based on the analysis of combined double and triple diagrams of PGE systems, the author considers possible ways of evolution of phase transformations of alloys of different composition.

Epifluorescence microscopy study of a quadruple node of triple junctions of grain boundaries in a Eu2+-decorated highly textured composite of (Cl, Br)(K, Rb) and I(K, Rb) solid solutions.

The structural nature and geometry, as well as the lattice-relative orientation, of an arrangement of crystal defects in a highly textured Eu2+-doped composite of two alkali-halide solid solutions was studied by epifluorescence microscopy (EFM) using the doping ion as a fluorochrome. A three-dimensional reconstruction and a skeleton type model, as built from a sequence of EFM images of different optical cross-sections of this arrangement, are presented. Structurally, this arrangement is a quadruple node (QN) of triple junctions of grain boundaries. The QN core geometry is that of a tetragonal tristetrahedron (TTTH), centred at the QN site, whose tetrahedron vertices and edges are on the QN triple junctions and grain boundaries, respectively, whereas the tristetrahedron tetragonal axis is nearly parallel to the lattice [001]-axis. The measured values of the angles between triple junctions and between the grain boundaries forming them are reported. The distinct chemical compositions of the composite solid solutions are discussed to be responsible, in last instance, for the tristetrahedron departure from a cubic configuration. Collaterally, certain families of translationally periodic almost-parallel (TPAP)-wall-like regions which consist of TPAP-columns of TPAP-spindle-like singularities, as well as certain zigzag arrays of columns of this like, existing into the QN grains, are reported to be observed. Three-dimensional reconstructions of typical individuals of these families and arrays as well as of their constituent parts are presented and geometrically analysed. These families and arrays are discussed to be families of tilt subboundaries, whose constituent dislocations are decorated by cylindrical second-phase europium di-halide precipitates, and regularly faceted tilt subboundaries, respectively. Crystal growing and sample preparation, composite structural characterisation by powder and single-slab X-ray diffraction (PXRD and SSXRD, respectively), microscopy and fluorescence-cube unit optics, image processing, electronic three-dimensional reconstruction and measuring methodologies, are all described in detail.

Obtaining of disordered highly ionic conductive Ag7+x(P1−xSix)S6 single crystalline materials

For the first time, bulk single crystals of the Ag7+x(P1−xSix)S6 solid solution were obtained via directional crystallization from the melt. The crystal structure of the Ag7+x(P1−xSix)S6 solid solution was determined by the Rietveld method. It was demonstrated that Ag7+x(P1−xSix)S6 solid solutions crystallize in two crystal systems—cubic and orthorhombic, and different SG: P213, F-43m and Pna21. The grown crystals were studied by SEM and EDS methods. The electrical parameters of Ag7+x(P1−xSix)S6 were studied in wide frequency and temperature ranges. Established that Ag7+x(P1−xSix)S6 solid solutions exhibit an increase in ionic conductivity compared to the initial compounds. Among the studied solid solutions, the Ag7.25P0.75Si0.25S6 sample demonstrated the highest conductivity with values reaching σion = 2.9 × 10−2 S/cm. The lowest activation energy value (Ea(ion) = 0.2 eV) is also observed for the given composition of solid solutions. The mechanism of ion transport is considered within the context of limiting distances and position occupancy.

Nonstoichiometry, thermal expansion and conductivity of Ba1-xPrxFe1-yCoyO3-δ solid solutions

Solid solutions Ba1-xPrxFe1-yCoyO3-δ (x = 0.3, y = 0.1–0.6 and x = 0.1–0.6, y = 0.2) with cubic structure were synthesized through a glycerol-nitrate technique. The oxygen content, thermal expansion, electrical conductivity and the Seebeck coefficient in the Ba1-xPrxFe1-yCoyO3-δ oxides were measured versus temperature in air. The oxygen content increases with increasing iron and praseodymium concentrations in Ba1-xPrxFe1-yCoyO3-δ. The value of the thermal expansion coefficient weakly depends on the composition of solid solutions. The conductivity of Ba1-xPrxFe1-yCoyO3-δ is practically independent of the concentration of 3d metals and increases significantly with increasing praseodymium content. The maximum conductivity value of 210 S/cm is obtained for Ba0.4Pr0.6Fe0.8Co0.2O3-δ at 450 °C in air. A positive value of the Seebeck coefficient indicates the predominant p-type conductivity in Ba1-xPrxFe1-yCoyO3-δ.

Local structure and phase composition of Neodymium-Zircon solid solution (NdxZr1-xSiO4-x/2)

To address the structural stability of host materials for immobilizing radioactive actinides in nuclear waste management applications, the present study is focused on the effect of various concentrations of Nd substitution on structural properties of synthetic zircon (NdxZr1-xSiO4-x/2). To achieve this, both pure and Nd-substituted zircon powders were prepared using the solid-state synthesis route. Rietveld refinement of X-ray Diffraction (XRD) data was employed to investigate the impact of various Nd substitutions on the phase composition of the zircon (ZrSiO4) crystal structure. This refined data was then utilized as input for the analysis of X-ray absorption spectroscopy (XAS) data. The results were further supported by observations from Raman spectroscopy, which indicated the substitution of Zr by Nd. In this work, we present an analysis of both regimes of XAS i.e. X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. Qualitative analysis of XANES data suggests that disorder in the samples increases with higher levels of Nd doping. Additionally, EXAFS analysis around Zr absorption edge also confirms an increased disorder in the system with higher Nd doping levels. However, EXAFS fitting around Nd edge indicated that disorder induced changes are more prominent and Nd–O bond is elongated as compared to Zr–O bond. This disorder in the system escalates at a Nd concentration of 10 atomic % (at %). An important finding of this study is the phase composition analysis using Rietveld refinement of XRD data. While XAS provided an insight into the changes in the local structure, the overall crystal structure remained unaffected even at a high doping of 10 at %. This work provides a comprehensive local structure analysis on this system. Such analysis would help in understanding the structural stability of the system and to determining the maximum loading of actinides in the host zircon for potential nuclear waste management applications.

Dual plate-like grains of (Ti, Zr)B2 and W2B5 toughened solid solution composites fabricated via in-situ reaction spark plasma sintering of (Ti, W)C and ZrB2 powders

Novel dual plate-like grains of (Ti, Zr)B2 and W2B5 toughened solid solution composites were fabricated by the in-situ reaction spark plasma sintering at 1800 °C using (Ti, W)C and ZrB2 powders. The composites were predominated and composed of the (Zr, Ti, W)C solid solutions and plate-like (Ti, Zr)B2. In the (Ti, W)C-ZrB2 reaction system, W promotes the anisotropic growth of (Ti, Zr)B2 grains, while Ti makes the formation reactions of WxBy thermodynamically feasible. When the addition of ZrB2 exceeds 40 mol%, W begins to be boronized into WxBy which is mainly composed of plate-like W2B5. The (Ti, W)C-50 mol% ZrB2 composite with dual plate-like grains of (Ti, Zr)B2 and W2B5 exhibited the best comprehensive mechanical properties of hardness of 26.5 GPa, flexural strength of 620 MPa, and fracture toughness of 6.6 MPa·m1/2, which provide a new approach for the enhanced toughness without the introducing of metal impurities.

Optical transition tuning of Er3+ in continuous tungsto-molybdate solid solution NaY(MoxW1-xO4)2 phosphors

Nowadays, the application scenarios of rare earth doped luminescent materials tend to be refined and complicated. The optical properties of rare earth doped materials are difficult to precisely control via the traditional design and synthesis methods, namely, changing doping concentration or preparative conditions. The aim of this study is to tune the optical transition properties of Er3+ in tungsto-molybdate NaY(MoxW1-xO4)2 (x = 0, 0.01, 0.1, 0.3, 0.5, 0.7, 0.9, 0.99 and 1.0) phosphors by changing the host matrix. The Er3+ doped continuous tungsto-molybdate solid solution NaY(MoxW1-xO4)2 phosphors were prepared via a solid state reaction technique at optimized calcination temperatures. The refractive indexes of the obtained solid solution samples were confirmed according to different models and compared. Subsequently, the optical transition intensity parameters, radiative transition rates and intrinsic radiative lifetimes of Er3+ in these solid solution phosphors were calculated in the framework of Judd-Ofelt theory. It was confirmed that the optical transition properties of Er3+ can be greatly tuned by the solid solution composition, and the tuning effects for different transitions are different. To validate the reliability of the Judd-Ofelt calculations, the temperature-dependent emission spectra of two green emissions of Er3+ for different solid solution samples were studied. It was found that the radiative transition rate ratios between two green emissions derived from theoretical calculations and experimental measurements are in reasonable agreement, thus proving that the optical transition calculations are reliable and the optical transition properties of Er3+ in the tungsto-molybdates can be tuned in a large range. This work reminds us of a new route for developing novel luminescence materials based on practical demands.

Сравнительный анализ химического состава и механических свойств различных участков сварного соединения дюралюмина, полученного сваркой трением с перемешиванием

Friction stir welding is an advanced method of joining various metals and alloys in the aircraft and mechanical engineering industries. This type of welding is used to join materials that are difficult to weld or not weldable by conventional methods. The high-strength D16 aluminum alloy is difficult to weld by fusion, which is associated with the formation of a dendritic structure in the fusion zone leading to a decrease in the mechanical strength of the joint. In the work, the microstructure and microhardness of a welded seam of the D16 aluminum alloy produced by friction stir welding was studied. Using scanning electron microscopy and optical metallography, the authors identified the presence of three zones: the weld core, the thermomechanical impact zone, and the heat effected zone. In the central part of the welded joint (in the core), a laminated onion ring structure was discovered. A change in the chemical composition of the aluminum solid solution was identified in different areas of the weld zones, as well as the presence of a concentration gradient within each zone. In the upper part of the welded seam, the solid solution is silicon-enriched and depleted in copper. Due to the solid solution depletion in alloying elements, the aluminum content in the solid solution in the zone of the welded joint is higher compared to the initial state. The microhardness values in different areas of the welded joint correlate with changes in the chemical composition. In the welded joint zone, a significant decrease in microhardness was found compared to the initial state, and a change in microhardness associated with the chemical composition gradient within each zone was also observed.

RESEARCH OF INFLUENCE OF MOLAR COMPOSITION ON ELECTRON MOBILITY IN ALUMINUM-GALLIUM ARSENIDE

Improvement in the technology of growing multicomponent semiconductors and the study of their potential applications contribute to the development of semiconductor devices with improved characteristics. Aluminum gallium arsenide is a promising three-component semiconductor in terms of crystal lattice matching, which caused a comprehensive study of the material in order to create high-performance electronic and optoelectronic devices on its basis. Predicting the prospects for creating devices based on certain materials requires a thorough knowledge, first of all, of their electrical properties.It should be noted that the possibilities of modeling the mobility of electrons in aluminum-gallium arsenide are not sufficiently disclosed in the scientific and technical literature. The aim of this work is to simulate the dependence of the electron mobility of the AlxGa1-xAs solid solution on the molar composition x.The simulation was carried out by the method of relaxation equations; based on the three-valley model of the conduction band. A technique is presented and a numerical experiment is carried out to determine the dependence of the mobility of charge carriers on the molar composition x of the solid solution. Attention is drawn to the peculiarity of modeling the processes of intervalley nonequivalent scattering, which corresponds to a significant convergence ofenergy valleys to each other. A model dependence of the Hall electron mobility in AlxGa1-xAs is obtained in the full range of molar composition values and compared with experimental results. Additional simulation results are presented that contribute to the understanding of the processes leading to the appearance of a specific feature of the dependence of the electron mobility on the molar composition of AlxGa1-xAs.A set of initial modeling parameters is determined, which provides good agreement with the experimental results considered in the work. The obtained results of numerical simulation open up opportunities for additional studies of the properties of aluminum-gallium arsenide. A technique for modeling the dependence of charge carrier mobility on the molar composition for three-component solid solutions is proposed.

Extending the solid solution range of sodium ferric pyrophosphate: Off‐stoichiometric Na3Fe2.5(P2O7)2 as a novel cathode for sodium‐ion batteries

AbstractIron‐based pyrophosphates are attractive cathodes for sodium‐ion batteries due to their large framework, cost‐effectiveness, and high energy density. However, the understanding of the crystal structure is scarce and only a limited candidates have been reported so far. In this work, we found for the first time that a continuous solid solution, Na4−αFe2+α/2(P2O7)2 (0 ≤ α ≤ 1, could be obtained by mutual substitution of cations at center‐symmetric Na3 and Na4 sites while keeping the crystal building blocks of anionic P2O7 unchanged. In particular, a novel off‐stoichiometric Na3Fe2.5(P2O7)2 is thus proposed, and its structure, energy storage mechanism, and electrochemical performance are extensively investigated to unveil the structure–function relationship. The as‐prepared off‐stoichiometric electrode delivers appealing performance with a reversible discharge capacity of 83 mAh g−1, a working voltage of 2.9 V (vs. Na+/Na), the retention of 89.2% of the initial capacity after 500 cycles, and enhanced rate capability of 51 mAh g−1 at a current density of 1600 mA g−1. This research shows that sodium ferric pyrophosphate could form extended solid solution composition and promising phase is concealed in the range of Na4−αFe2+α/2(P2O7)2, offering more chances for exploration of new cathode materials for the construction of high‐performance SIBs.

Synthesis and characterization of a new (Ti1-yCuy)2(Al1-xCux)C MAX phase solid solution

New [Ti(1-y)Cuy]2[Al(1-x)Cux]C solid solutions have been synthesized by solid-state reaction performed at 760 and 800 °C on compacted Ti2AlC-40 vol % Cu composite particles produced by mechanical milling. Using XRD and EDXS, it is demonstrated that Cu atoms can enter the crystallographic structure of the Ti2AlC MAX phase, whereas a Cu(Al) solid solution is formed during thermal treatment. A selective chemical etching of the Cu(Al) matrix is performed to determine the composition of the MAX phase solid solution by analyzing the filtrate and the solid phase using ICP-OES end EDXS methods respectively. (Ti0.85Cu0.15)2(Al0.75Cu0.25)C and (Ti0.85Cu0.15)2(Al0.58Cu0.42)C solid solutions are formed after thermal treatment at 760 and 800 °C, respectively. The substitution rate on the A site of the MAX phase thus increases with temperature.