Scandium Content Research Articles

Ab initio study of domain structures in half-metallic CoTi1−xMnxSb and thermoelectric CoTi1−xScxSb half-Heusler alloys

We present first-principles calculations of the electronic density of state, the structures in CoTi1−xScxSb and CoTi1−xMnxSb. In addition for the latter we calculate magnetic moments. Systems with different stoichiometries are compared and low energy configurations are determined using a cluster expansion procedure. For all studied manganese concentrations, x>0, CoTi1−xMnxSb is half-metallic and magnetic, which make it interesting for spintronic applications. In contrast, with increasing scandium concentration, the band gap of CoTixSc1–xSb closes continuously, while the material changes from a semiconductor to a non-magnetic metal. For low Sc doping this material is well suited for thermoelectric applications. The electronic states close to the Fermi energy are strongly influenced by the distribution of Ti and Mn (or Ti and Sc). This has important consequences for the usage of materials in application fields like spintronics and thermoelectrics. In general, a phase separation of the alloys into a Ti rich and a Ti poor phase is energetically favored. Using mean field theory we create a phase diagram that shows the coexistence and the spinodal region. A spontaneous demixing can be used for the creation of nanodomains within the material. In the case of CoTi1−xScxSb, the resulting reduced lattice thermal conductivity is beneficial for thermoelectric applications, while in CoTi1−xMnxSb the nanodomains are detrimental for polarization.

Modes of occurrence of scandium in coals and peats (A review)

The modes of occurrence of scandium in peat and coal from different deposits in Siberia, Russian Far East, Kazakhstan, and Mongolia was studied with the use of a set of methods. The fractions of coal with different densities and the group components of peat and brown coal were considered. The selective leaching of Sc from brown coal and black coal with ammonium acetate and concentrated acids was performed, and a correlation between the Sc content and the ash content was studied. It was established that, at the early stages of a coal-formation process, the bulk of scandium in low- and medium-ash peats and brown coal was bound to organic matter. Humic substances (fulvic acids + humic acids) are the main carriers and concentrators of scandium. In all cases, the scandium content of humic acids was higher than the average concentration in peat and brown coal. A decrease in the yield of humic acid fractions in the coalification process decreases their fraction in the total balance of scandium; however, the fraction of insoluble humic substances increases in this case. The modes of occurrence of scandium changes in the course of coalification. In low-rank black coal (grade D), a considerable fraction of scandium occurs in the organic matter. The mineral forms of scandium predominate in mature black coal. Scandium is a constituent of silicates, aluminosilicates, phosphates, and aluminophosphates; it likely forms its own mineral species.

Effect of isovalent substitution on phase transition and negative thermal expansion of In2−xScxW3O12 ceramics

Solid solutions of In2−xScxW3O12 (0≤x≤2) were successfully synthesized using the solid state reaction method. Effects of substituted scandium content on the phase composition, microstructure, phase transition temperatures and thermal expansion behaviors of the resulting In2−xScxW3O12 (0≤x≤2) samples were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and thermal mechanical analyzer (TMA). Results indicate that the obtained In2W3O12 ceramic undergoes a structure phase transition from monoclinic to orthorhombic at 248°C. This phase transition temperature of In2W3O12 can be easily shifted to a lower temperature by partly substituting the In3+ with Sc3+. When the x value increased from 0 to 1, the phase transition temperatures of In2−xScxW3O12 (0≤x≤2) samples decreased from 248 to 47°C. All the In2−xScxW3O12 (0≤x≤2) ceramics show fine negative thermal expansion below their corresponding phase transition temperatures. The negative thermal expansion coefficients of the In2−xScxW3O12 (0≤x≤2) ceramics change in the range from −1.08×10−6°C−1 to −7.13×10−6°C−1.

Экстракция скандия расплавом ди-2-этилгексилфосфорной кислоты в легкоплавких разбавителях

Currently widespread distribution of extraction methods using fusible reagents can be explained by a number of advantages, such as high kinetic characteristics of the process, the ease separation of two phases, high selectivity of many extractants, relatively complete regeneration. For the extraction of scandium in technological order, neutral and cation exchange extractants can be used. Several extraction reagents melt easily at high temperatures, and such melts can be used for extraction. Efficiency of the extraction of metal by cation reagents depends on many factors. Extraction of scandium by melt mixtures of di-2-ethylhexylphosphoric acid - higher carboxylic acid - paraffin and the effect of acidity of the aqueous phase, the concentration of scandium and the aqueous extractant in the organic phase, the volume ratio of organic and aqueous phases on the extraction of metal were studied. It was found that the extraction of scandium proceeds through the cation exchange mechanism. Scandium was extracted quantitatively (> 99.0%) from acid solutions. The optimal concentration of di-2-ethylhexylphosphoric acid in the extractant was 0,250 M, quantitative extraction of scandium was observed in the range of its concentrations of 10 -3 -10 -6 M and the volume ratio of organic phases to aqueous phases of 1:5 - 1:20.

Concentration of Scandium during Processing the Distillate of Production of the Aluminum–Scandium Foundry Alloy

The composition and characteristics of the sublimate of the aluminum–scandium Al–2%Sc master-alloy production are investigated using electron microscopy, electron probe microanalysis, X-ray phase analysis, and inductively coupled plasma emission spectroscopy. It is established that the sublimate consists of particles 1–5 μm in size by 60 %; the coarser of them have a shell, inside which, inclusions (segments, particles, pieces) of various phases are present. The sublimate consists of metal aluminum (~35 %), two modifications of aluminum fluoride (~57 % total), and the rest is corundum. The scandium content is 0,5–0,6 wt %. It is shown that the use of hydrometallurgic methods is reasonable for its processing. The method of preparing «rich» concentrate with 3–11 wt % Sc from this type of waste by the treatment of the sublimate with the 10-% caustic soda solution at 80 °C is proposed.

THE EFFECT OF ENVIRONMENT PH ON ANODIC BEHAVIOR OF ZN55AL ALLOY DOPED WITH SCANDIUM

The anodic behavior of Zn55Al alloy doped with scandium has been studied. The scandium content dependence of the Zn55Al alloy corrosion potential shows the extreme character. The increase in the chloride ion concentration in the electrolyte reduces the corrosion potential. When doping element content grows in the alloys, pitting and repassivation potentials are shifted to the positive area, and when chloride ion concentration grows, the potentials are shifted to the negative area over the entire range of environment pH. Zn55Al alloy corrosion rate decreases 2–3 times in doping 0,005–0,05 wt.% scandium. Thus the alloys of such composition can be recommended as anode coating for corrosion protection of steel structures, components, and constructions.

Lab Scale Synthesis of Al-Sc Alloys in NaF-AlF<sub>3</sub>-Al<sub>2</sub>O<sub>3</sub>-Sc<sub>2</sub>O<sub>3</sub> Melt

The liquidus temperature in the [NaF-AlF3(30 mol.%)]-Sc2O3 molten system with the Sc2O3 additions up to 12 wt% was measured by the thermo analysis. The effect of the cathode current density (0, 0.25, 0.50, and 1.0 A∙cm-2), the Sc2O3 content (1, 2, 4, and 8 wt%) in the NaF-AlF3(30 mol.%)-Al2O3-Sc2O3 electrolyte, the rate of the molten aluminum agitation (0, 100 rotates/min), the synthesis duration (30-210 min) on the Sc content in the aluminum alloy at 980 °С was studied. The Al-Sc alloys with the scandium content of 0.15-1.30 wt%, depending on the synthesis conditions, and with the uniform Sc distribution throughout the aluminum matrix were produced.

Rare Earths in Geological Formations of Central Region of the Dniester River Basin, Republic of Moldova

In the different varieties of crystalline basement of Archean and Proterozoic age and in Vendian (Ediacaran) basal layers of platform coverture in the Central Basin of the Dniester River were found relatively high concentrations of Lanthanum, Cerium, Yttrium, Ytterbium, and Scandium. Because the petrographic formations, which are genetic associated with RE elements in Dniester region are absent, the origin of these elements is unclear. At the same time, in the geological mapping, it was detect that geochemical aureoles of REE, found in the northern region of Republic of Moldova, are generated by accessory minerals monazite and zircon present in the rock of basement platform and fragments of crystalline rock in the composition of terrigenous formations from basal levels of sedimentary coverture. Probably mentioned minerals are brought from Ukrainian Crystalline Shield regions, in which are spread varieties of granitic rocks and alkaline pegmatite. It is not excluded that in these basal layers in the sedimentogenes processes and differentiation of detrital material to be formed the mechanic aureoles rich in monazite and zircon, which in turn can form significant concentrations of rare earths. To solve the perspective problem of detection of industrial mineral accumulations of RE in the central region of the Dniester River basin, it is necessary to conduct within this area detailed geological and geochemical research.

Concentration of scandium during processing the sublimate of production of the aluminum-scandium master alloy

The composition and characteristics of the sublimate of the aluminum-scandium Al-2%Sc master alloy production are investigated using electron microscopy, microprobe analysis, derivatography, X-ray analysis, and emisionno-spectral method with inductively coupled plasma. It is established that 98% of the sublimate consists of particles 1–2 μm in size; the coarser ones have a shell in which inclusions (segments, particles, and pieces) of various phases are present. The sublimate consists of metal aluminum (∼35%), two polymorphs of aluminum fluoride (∼57% total), and the rest is corundum. The scandium content is 0.5–0.6 wt %. It is shown that the use of hydrometallurgic methods is reasonable for its processing. The method of preparing a “rich” concentrate with 3–11 wt % Sc from this type of waste by treating the sublimate with a 10% caustic soda solution at 80°C is proposed.

Solubility polytherms and eutectic concentrations of scandium, yttrium, and lanthanum perchlorate solutions

Freezing points of solutions M(ClO4)3-H2O (M = Sc, Y, La) of different concentrations were determined. The solubility polytherms of the perchlorate systems studied, as well as aluminum, gallium, and indium perchlorates were compared with the concentration dependences of different properties of the corresponding solutions. Viscometry and IR spectroscopy allowed the special points on these dependences to be correlated with eutectic concentrations. Structural changes in the systems studied as a function of solute concentration were described.

Scandium induced structural transformation and B′:B″ cationic ordering in Pb(Fe0.5Nb0.5)O3 multiferroic ceramics

The current study explores non-magnetic Sc3+ induced structural transformation, evolution of local B-site cation ordering and associated effect on ferroelectric phase transition temperature Tmax (temperature corresponding to dielectric maxima) on increasing the atom percent of Sc substitution in [Pb(Fe0.5Nb0.5)O3 (PFN)] ceramics. In this regard, the phase pure Pb[(Fe0.5−xScx)Nb0.5]O3 ceramics with x varying from 0 to 0.5 were synthesized through solid state reaction route. The detailed structural analysis through Rietveld refinement confirms the room temperature transformation from a monoclinic Cm to rhombohedral R3m structure at x = 0.3 mol. % of Sc. Absorption spectra studies show that there is a considerable increment in the bandgap at higher scandium content. Most interestingly, the Tmax exhibited an increment for lower scandium contents (x = 0.1 to 0.25) followed by a drop in Tmax (x = 0.3 to 0.5). Such anomalous behavior in Tmax is expected to arise due to the onset of B′, B″ local cation ordering beyond Sc content x = 0.25. The B-site cation ordering at and beyond x = 0.3 was also confirmed by the evolution of cation order induced Pb-O coupled vibrational mode in Raman scattering studies. In addition, the Mössbauer spectra of PFN (x = 0) and Pb(Fe0.4Sc0.1Nb0.5)O3 (x = 0.1) are reported to verify the spin state and oxidation state of iron. The lattice distortion due to the radius ratio difference between a Sc3+ cation and Fe3+ cation in low spin state is responsible for the structural transformation, which in turn facilitates a B′:B″ cation ordering.

Soft chemistry synthesis of powders in the BaF2-ScF3 system

The BaF2-ScF3 system is studied using coprecipitation from aqueous solutions. Compound Ba3Sc2F12 is found to form over a wide range (10–60 mol %) of scandium concentrations in the initial solution. At higher scandium concentrations in solution, a new phase of provisional composition BaSc2F8 · 2H2O (hexagonal system, a = 9.6346 A, c = 4.0483 A) was obtained. Scandium fluoride hydrolysis is not observed by energy-dispersive X-ray analysis.

Effect of prior cold work on tensile properties of Al–6Mg alloy with minor scandium additions

Effect of aging on the mechanical properties of cold worked Al–6Mg alloy with minor additions of scandium is studied. Cast and mechanically worked samples are isochronally aged for 60 min at different temperatures up to 500°C. Evaluation of mechanical properties of the aged alloys is done at various strain rates of testing. The m-values (strain rate sensitivity) of the experimental alloys are desired from the tensile test results. The influence of scandium is much pronounced on yield strength than on the tensile strength. Alloys with higher scandium content have shown higher yield strength. The ‘m’ values are found to be comparatively high at peak aged condition of alloy with higher scandium content. The fracture of the experimental alloys occurs through microvoid coalescence.On étudie l’effet du vieillissement sur les propriétés mécaniques de l’alliage écroui d’Al-6Mg avec additions mineures de scandium. On a vieilli à durée égale pendant 60 minutes à différentes températures, jusqu’à 500°C, des échantillons moulés et formés mécaniquement. On fait l’évaluation des propriétés mécaniques des alliages vieillis par essai à différentes vitesses de déformation. On désire les valeurs de m (sensibilité à la vitesse de déformation) des alliages expérimentaux à partir des résultats de l’essai de traction. L’influence du scandium est beaucoup plus prononcée sur la limite d’élasticité que sur la résistance à la traction. Les alliages ayant une teneur plus élevée en scandium ont montré une limite d’élasticité plus élevée. On a trouvé que les valeurs de ″m″ étaient comparativement élevées sous la condition maximale de vieillissement de l’alliage ayant la teneur la plus élevée en scandium. La rupture des alliages expérimentaux se produisait par cupulation.

Scandium resonant impurity level in PbTe

We synthesize a scandium-doped PbTe single-crystal ingot and investigate the phase and the elemental composition as well as galvanomagnetic properties of Pb1-yScyTe alloys in weak magnetic fields (4.2 K ≤ T ≤ 300 K, B ≤ 0.07 T) upon varying the scandium content (y ≤ 0.02). We find that all investigated samples are single-phase and n-type. The distribution of scandium impurities along the axis of the ingot is estimated to be exponential. An increase of scandium impurity content leads to a monotonous growth of the free electron concentration by four orders of magnitude (approximately from 1016 cm−3 to 1020 cm−3). In heavily doped alloys (y > 0.01), the free electron concentration at the liquid-helium temperature tends to saturation, indicating the pinning of the Fermi energy by the scandium resonant impurity level located on the background of the conduction band. Using the two-band Kane and six-band Dimmock dispersion relations for IV-VI semiconductors, dependences of the Fermi energy measured from the bottom of the conduction band Ec on the scandium impurity content are calculated and the energy of the resonant scandium level is estimated to be ESc ≈ Ec + 280 meV. Diagrams of electronic structure rearrangement of Pb1-yScyTe alloys upon doping are proposed.

Influence of c-axis orientation and scandium concentration on infrared active modes of magnetron sputtered ScxAl1−xN thin films

Doping of wurtzite aluminium nitride (AlN) with scandium (Sc) significantly enhances the piezoelectric properties of AlN. ScxAl1−xN thin films with different Sc concentrations (x = 0 to 0.15) were deposited by DC reactive magnetron sputtering. Infrared (IR) absorbance spectroscopy was applied to investigate the Sc concentration dependent shift of the IR active modes E1(TO) and A1(TO). These results are compared to ab initio simulations, being in excellent agreement with the experimental findings. In addition, IR spectroscopy is established as an economical and fast method to distinguish between thin films with a high degree of c-axis orientation and those exhibiting mixed orientations.

Characterization and Piezoelectric Properties of Reactively Sputtered (Sc, Al)N Thin Films on Diamond Structure

Highly oriented wurtzite (Sc, Al)N films were deposited on a diamond/silicon by a co‐sputtering system. The results showed that the formation of ScxAl1−xN alloys causes a lattice distortion during the phase transition, and this intermediate phase induces a large piezoelectric response. When the scandium concentration increased up to the solution limit of scandium in aluminum nitride (measured data are about 12 at.%), the piezoelectric coefficient of (Sc, Al)N film is four times larger than pure AlN layer. After annealing process, the d33 value of (Sc, Al)N can be increased to a maximum of 20.073 pC/N.

Experimental Study on Extraction of Scandium from Hydrochloride Acid Leaching Liquid in TBP

The scandium concentrate used in the leaching experiment was obtained from the rare earth ore containing scandium in Yunnan Province, the sample used in experiment is leaching liquid containing scandium which the content of scandium is 3.6g/t, with complex impurity composition. The main influencing factors of extraction in hydrochloric acid solution were acidity, mixing time, phase ratio etc. and the condition experiments about these factors were conducted. The results show that extraction of scandium from the hydrochloric acid solution in TBP is feasible. The optimal conditions are that pH of the solution is 1.26, dosage of TBP is 5% of the solution, dosage of kerosene is 10% of TBP, mixing time is 3 min, phase ratio is 1:10, washing time is 2, the oscillating time of stripping is 1~2 min and the stripping rate reach 99.89%.

Enhanced Mechanical Properties of AA5083 GTA Weldments with Current Pulsing and Addition of Scandium

AA5083 alloy is welded with gas tungsten arc welding using optimized welding parameters. Al-Si-Sc master alloy filler with varying contents of scandium is used for welding. Welding was carried out with and without AC-pulsed current techniques. A narrow heat affected zone with more refined grain structure is observed in the case of the pulsed current technique. Furthermore, it is observed that the columnar solidification structure in the fusion zone was suppressed and fine equiaxed grains were formed in the weld zone with increasing scandium content, which is attributed to the grain refinement effect of scandium with the generation of increased nucleating sites during weld solidification. This effect is reflected in mechanical properties also. An increased hardness of about 10 % results with pulsed current technique compared to about 20 % with an addition of 0.75 % scandium. However, in the case of tensile properties pulsing resulted in about 8 % increase in tensile strength and addition of 0.75 % scandium resulted in about 40 % increase in tensile strength. Both the pulsed current technique and the addition of scandium were observed to be better in increasing not only strength but also elongation due to the refined grain structure in the weld fusion zone.

Application of a Partial Least Squares Regression for the Determination of Nanomolar Concentrations of Scandium in the Presence of Nickel by Adsorptive Stripping Voltammetry

AbstractThis paper presents the methodology of a very sensitive determination of scandium in excess of nickel by adsorptive stripping voltammetry on a mercury film electrode and PLS regression. A calibration set consisting of binary mixtures containing 5, 15, 25, 35 or 45×10−9 M Sc(III) and simultaneously 0.5–50×10−7 M of Ni(II) was used to develop the chemometric PLS calibrations. An external set containing synthetic mixtures of 10, 20, 30, 40×10−9 M Sc(III) and the same Ni(II) concentration as mentioned above was used to validate the model and evaluate predictive ability. The application of data pretreatment techniques involving baseline correction, smoothing, range‐scaling, mean‐centering and their influence on the PLS model complexity, were also investigated. In the effect, the model for Sc(III), including 6 latent variables, was constructed. The model fulfills validation criteria and is characterized by a good prediction ability (majority of the prediction errors are lower than 10%). This work shows significant progress in the development of a very sensitive analytical technique for the determination of scandium in the presence of different concentrations of nickel by application of multivariate calibration tools.

Influence of scandium concentration on power generation figure of merit of scandium aluminum nitride thin films

The authors have investigated the influence of scandium concentration on the power generation figure of merit (FOM) of scandium aluminum nitride (ScxAl1−xN) films prepared by cosputtering. The power generation FOM strongly depends on the scandium concentration. The FOM of Sc0.41Al0.59N film was 67 GPa, indicating that the FOM is five times larger than that of AlN. The FOM of Sc0.41Al0.59N film is higher than those of lead zirconate titanate and Pb(Mg1/3Nb2/3)O3-PbTiO3 films, which is the highest reported for any piezoelectric thin films. The high FOM of Sc0.41Al0.59N film is due to the high d31 and the low relative permittivity.