Solid Solution Region Research Articles

Synthesis of the AgBr – AgI system optical crystals

Abstract The presented work is devoted to the study and development of the technology for obtaining the AgBr – AgI crystals system. Studies have been carried out to study the phase diagram in order to clarify the region of stable solid solutions' existence. Based on the data obtained, the modes were selected and single crystals of various compositions were synthesized. Their main optical properties, such as the spectral transmission range, were investigated and the refractive indices were determined at the wavelength of the short-wave absorption edge and the CO2 laser (10.6 μm). The work’ results are necessary for the manufacture of various structures IR fibers, windows, lenses, and other optical products, which are widely used in different fields of science and technology, including laser, endoscopic, and diagnostic medicine.

Low‐temperature phase formation in the SrF2–LaF3 system

AbstractPhase formation in the SrF2–LaF3 system was studied at temperatures ranging from 300°C to 450°C using nitrate flux. The solubility of LaF3 in SrF2 decreases with decreasing temperature. The equilibrium width of the solid solution region Sr1−xLaxF2+x at 400°C, it is 44.6 ± 0.4 mol% LaF3 (x = 0.446), at 350°C — 38.3 ± 0.7 mol% LaF3 (x = 0.383), and decreases almost to zero at 300°C.

ФИЗИКО-ХИМИЧЕСКОЕ ИССЛЕДОВАНИЕ СИСТЕМЫ Bi2Te3-Ho2Тe3

The chemical interactions in the Bi2Te3-Ho2Te3 system are investigated by methods of physicochemical analysis (DTA, XRD, MSA, microhardness measurements and density determination), a state diagram is constructed. As a result, it was revealed that the system state diagram is a quasi-binary eutectic type. In the Bi2Te3Ho2Te3 system, in a 1: 1 ratio of components, one ternary compound of the HoBiTe3 composition, incongruently melting at 610°C, is formed. According to the results of X-ray phase analysis, it was found that the HoBiTe3 compound crystallizes in the tetragonal system with lattice parameters: a = 19.99; c = 13.82 Å, Z = 3, density ρpikn. = 7.30 g/cm3 ρrent. = 7.35 g/cm3.On the basis of the initial components, regions of solid solutions were found, which on the basis of Bi2Te3 reach 5 mol % Ho2Te3, and on the basis of Ho2Te3 -3 mol % Bi2Te3. Compounds Bi2Te3 and Ho2Te3 form a eutectic with a composition of 20 mol % Ho2Te3 and a temperature of 465°C.

Physicochemical Analysis of the FeSe–Ga2Se3–In2Se3 System

Phase equilibria in the FeSe–Ga2Se3–In2Se3 system were studied by differential thermal analysis and X-ray powder diffraction analysis. A number of polythermal sections, the isothermal section at 1000 K, and the projection of the liquidus surface of the phase diagram were constructed. It was determined that this system is quasi-ternary, and that the liquidus surface comprises the fields of primary crystallization of six phases. The types and coordinates of invariant and monovariant equilibria were found. Wide regions of solid solutions based on binary and ternary compounds (FeGa2Se4, FeIn2Se4) were revealed, being of interest as magnetic materials.

Phase Equilibria in BaS–In2S3 System

A confined region of solid solution exists in BaS−In2S3 system of eutectic type with incongruent melting compounds of BaIn2S4 and Ba2In2S5 composition based on the α modification of In2S3. Compounds BaIn2S4 and Ba2In2S5 melt incongruently at 1330 and 1497 K, crystallize in rhombic syngony with unit cell parameters а = 2.181 nm, b = 2.165 nm, с = 1.311 nm (space group Fddd) and а = 1.317 nm, b = 1.272 nm, с = 1.178 nm (space group Pbca), respectively. Microhardness H = 2470 MPa for BaIn2S4 and 2250 MPa for Ba2In2S5. Coordinates of BaIn2S4–In2S3 eutectics is 76 mol % In2S3, Tm = 1190 K. Solubility of BaS in α-In2S3 at 1070 K reaches 2 mol % BaS. Solubility of BaS in α-In2S3 decreases with temperature and becomes 1 mol % BaS at 870 K.

Large Delta T Thermal Cycling Induced Stress Accelerates Equilibrium and Transformation in Super DSS

Based on the predicted phase diagram of super duplex stainless steel (DSS) calculated by Thermo-Calc, the maximum peak temperature 1100 °C was selected to ensure no σ phase existence. This target temperature fell into the two-phase solid solution (SS) region. A series of different thermal cycling tests were carried out with the notations of 2SS, 2SS + 3 cycles, 2SS + 7 cycles, 2SS + 13 cycles, and 2SS + 20 cycles. It was found that the trend of two-phase volume ratio variation by thermal cycling followed the predicted thermodynamic equilibrium trend. After 2SS + 7 cycles, the ratio of two-phase δ/γ tended toward the ideal 1:1. According to the electron backscatter diffraction (EBSD) analysis, the δ phase crystal orientation changed from the most frequent directions of <001> and <111> of the as-received sample to the most frequent orientation of <113> after two SS treatments. While the γ phase grain always remained at <101> orientation. The grain boundary misorientation angles of the γ grains were relatively stable, ranging from 53° to 63°, but those of the δ grains were widely distributed actively presuming the lattice rotation. The Kernel Average Misorientation (KAM) value of the local strain in face center cubic (fcc) γ grains was varied and greater than that of the body center cubic (bcc) δ phase, indicating that the former, with a large grain boundary misorientation had larger local deformation than the latter, which possesses wide random misorientation angle distribution.

Investigation of the Chemical Interaction in the Sb2Te3–InSe System and the Properties of the Obtained Phases

The interaction in the Sb2Te3–InSe system was studied and the T–x phase diagram was constructed by integrated methods of physicochemical analysis (differential thermal, X-ray powder diffraction, and microstructural analyses) and also by microhardness and density measurements. It was found that the Sb2Se3–InSe system is a quasi-binary section of the ternary reciprocal system Sb,In||Se,Te. In the Sb2Te3–InSe system, compounds InSb2SeTe3 and In3Sb2Se3Te3 form, which incongruently melt at 525 and 600°C, respectively. It was found that the regions of solid solutions based on Sb2Te3 and InSe extend to 3 and 2 mol %, respectively. The compounds Sb2Se3 and InSe form a eutectic with the coordinates 20 mol % InSe and 510°C. The temperature dependences of the electrical conductivity and thermal emf of the solid solutions (Sb2Te3)1 – x(InSe)x (x = 0.01, 0.02, and 0.03).

Calibration of a QEM-EDS system for rapid determination of potassium concentrations of feldspar grains used in optical dating

Potassium (K)-rich feldspars are one of two mineral types typically used for optical dating. Feldspar grains can contain up to ~14 wt% K that gives rise to an internal dose rate component. This internal component can comprise a significant proportion of the total environmental dose rate to which a mineral grain is exposed. The environmental dose rate term—the denominator in the optical age equation—determines the rate at which electronic charge is transferred into the crystal lattice of a mineral grain over its period of burial. Not all feldspar grains have the same K concentration, so internal dose rates differ between individual grains. K concentrations can range from 0 to 14 wt% due to the variable compositions of feldspar phases, differing proportions of discrete feldspar phases and/or the presence of other mineral inclusions in grains. Numerous techniques are available for determining the K concentrations of individual grains, but are time-consuming, and either lack the spatial resolution to classify discrete mineral phases within multi-phase grains, or the coverage to obtain whole-of-grain average K concentrations. Quantitative evaluation of minerals using energy dispersive spectroscopy (QEM-EDS) is a time-efficient and automated mapping technique that has the spatial resolution to classify most mineral phases, as well as the coverage to determine their area proportions. QEM-EDS can also be used to determine elemental concentrations based on spectral matches to EDS reference spectra. It is, however, difficult to determine accurate elemental concentrations for minerals such as feldspars, where solid solutions exist. To overcome this, we establish a QEM-EDS calibration using EDS spectra from six feldspar reference standards to define five solid solution regions along the alkali and plagioclase feldspar series. We test this calibration through comparisons of the K concentrations of discrete phases of three feldspar varieties (orthoclase/microcline, albite and sanidine), derived using both QEM-EDS and wavelength dispersive spectroscopy (WDS). We assume that the WDS-derived K concentrations represent the ‘true’ K concentrations of the phases, and calculate, from a best-fit weighted regression of the two data sets, a correction and uncertainty estimate that can be applied to the QEM-EDS-derived K concentrations, taking into account instrument irreproducibility and any measurement bias. We also test alternative mapping step sizes to optimise efficiency, and apply this time-efficient technique to individual luminescent feldspar grains from two samples. We propose that QEM-EDS is capable of (1) classifying the range of mineral phases in grains, (2) determining the area proportions of each of these phases, and (3) obtaining accurate whole-of-grain average K concentrations of individual feldspar grains using the calibration and correction presented here.

QUASIBINAR SECTION OF AgGaS2-AgSbS2

The aim of this work is to study phase equilibrium and build a state diagram of the AgGaS2-AgSbS2 system. For research, the initial sulfides (AgGaS2 and AgSbS2) were synthesized from elements of high purity in quartz ampoules evacuated to 0.133 Pa. Quaternary alloys of the AgGaS2 – AgSbS2 systems were synthesized from ligatures at a temperature of 800–1300 K, depending on the composition. To homogenize the alloys, annealing was performed at 50–60 K below solidus for 300 h. Using complex methods of physicochemical analysis (differential thermal, X-ray phase, microstructural, microhardness measurement and density determination), phase equilibria in the AgGaS2-AgSbS2 system were studied. It was established that the AgGaS2-AgSbS2 system is a quasibinary section of the eutectic type and its state diagram is constructed. The coordinates of the eutectic correspond to 65 mol. % AgSbS2 and a temperature of 750 K. Based on the starting components in the section, the regions of solid solutions were determined. At room temperature, the regions of solid solutions based on AgGaS2 (8 mol. % AgSbS2) and based on AgSbS2 (14 mol. % AgGaS2) were revealed. At a eutectic temperature, solubility reaches 20 and 25 mol. %, respectively. According to the XRD data, α-solid solutions belong to monoclinic syngony, and with an increase in the concentration of AgGaS2, the lattice parameter increases (a = 12.861-12.972; b = 4.409-4.474; c = 13.282-13.324Å). AgSbS2 triple sulfide solid solutions crystallize in monoclinic syngony. These solid solutions are of the type of substitution. For structural and optical measurements, technological conditions for the growth of crystals of solid solutions were developed and their single crystals were grown. Single crystals of (AgSbS2)1-x(AgGaS2)x solid solutions were obtained by the Bridgman-Stockbarger method.

Lithium cation conductivity of solid solutions in Li6-2xMxZr2O7 (M = Mg, Ca, Zn) systems

Glycine-nitrate method is used to synthesize samples in Li6-2xMxZr2O7 (M = Mg, Ca, Zn) systems. Boundaries of single-phase regions of solid solutions based on monoclinic Li6Zr2O7 are roughly determined, temperature dependencies across the range of 300–600°С and concentration dependencies of their conductivity are studied. The maximum lithium cation conductivity of the synthesized solid solutions exceeds the conductivity of undoped Li6Zr2O7 by more than two orders of magnitude. The obtained results are compared with the available literature data on the transport properties of Li6Zr2O7 and solid solutions based on it. The influence of electronegativity of M dopants on the transport properties of the investigated solid electrolytes is studied.

Limits of Solid Solutions and Thermal Deformations in the L-Alanine–L-Serine Amino Acid System

The limits of solid solutions and thermal deformations in the L-alanine–L-serine (L-ala–L-ser) amino acid system have been determined. Thirteen amino acid mixtures with various proportions of the components L-ser/L-ala were studied using powder X-ray diffraction techniques. It was found that the regions of solid solutions in the system are rather limited and cover less than 10 mol. % from each component side. The thermal behavior of the components L-ser and L-ala and the composition L-ser/L-ala = 90/10 were studied by temperature-resolved powder X-ray diffraction. The heating of L-ser and L-ala only causes thermal deformations, while two-phase mixtures with the 90/10 L-ser/L-ala ratio form solid solutions at elevated temperatures. Additionally, the parameters of the thermal deformation tensor for L-ser and L-ala were calculated, and the figures of their thermal expansion coefficients were plotted and analyzed. The study conducted is of high applicability, since amino acids are active components of various biological, geological, and technological processes, including those at elevated temperatures, and have numerous applications in life-science industries.

Crystal chemistry and phase equilibria of the CaO-½Ho2O3-CoOz system at 885 °C in air

The phase equilibrium diagram of the CaO-½Ho2O3-CoOz system was determined at 885 °C in air. This diagram offers compatibility relationships in the ternary oxide system that are essential for processing and for the understanding of properties of several thermoelectric phases in the system. Four three-phase regions and three solid solution tie-line regions were determined in the CaO-½Ho2O3-CoOz system. In the CaO-Ho2O3 system, while a small solid solution region was identified for (Ho1-xCax)O(3-z)/2 (0 ≤x ≤ 0.14), Ho was not present in the Ca site of CaO. Neither the reported Ho2CoO4 phase in the Ho2O-CoOz system nor the Ca-doped (Ho1+xCa1-x)CoO4-z phase was present at 885 °C. No solid solution of the distorted perovskite, (Ho1-xCax)CoO3-z, was established at this temperature. The CaO-CoOz system consists of two calcium cobaltate thermoelectric compounds. The 2D thermoelectric oxide, (Ca3-xHox)Co4O9-z (0 ≤x ≤ 0.5), has a misfit layered structure, and the 1D Ca3Co2O6 consists of chains of alternating CoO6 trigonal prisms and CoO6 octahedra. Ca3Co2O6 was found to be a stoichiometric compound. A comparison of the phase diagrams of the CaO-½R2O3-CoOz (R = La, Nd, Eu, and Ho) systems is given.

Experimental investigation of the phase relations in the SiO2-Dy2O3-CaO ternary system

This paper reports on the experimental investigation of the phase relations in the CaO-SiO2-Dy2O3 system. CaO-SiO2-Dy2O3 slags were equilibrated at 1773 and 1873 K for 86400 s in Ar and then quenched in water to determine the phase relations of the system. The composition of the equilibrated phases was measured by EPMA-WDS and XRD. The presence of ternary compounds and the solid solution and liquid regions were determined to construct the isothermal sections at 1773 and 1873 K of the ternary phase diagram. The data from this work will support further investigations on the feasibility to recover REEs through pyrometallurgical processing.

Electrochemical properties and evolution of the phase transformation behavior in the NASICON-type Na3+xMnxV2-x(PO4)3 (0≤x≤1) cathodes for Na-ion batteries

NASICON-structured cathode materials are considered as possible candidates for high-performance Na-ion batteries. Further increase of energy density of the Na3V2(PO4)3 may be achieved by substitution of the V cations by other transition metals. Here, we show that a family of Na3+xMnxV2-x(PO4)3 (0≤x≤1, Δx=0.2) cathode materials demonstrates remarkable diversity of the electrochemical properties and phase transformations depending on degree of substitution and cut-off voltage. An intermediate “Na2M2(PO4)3” phase was found for all compounds studied by means of operando powder X-ray diffraction. When Mn content is low (x~0–0.4), it coexists with Na3+xMnxV2-x(PO4)3 or Na1+xMnxV2-x(PO4)3. Increase in Mn content extends the length of the solid solution region corresponding to sodiated, intermediate and desodiated phases. All Mn-substituted samples are characterized by additional high-voltage plateau (~3.9 V) at charge-discharge curves. Na3+xMnxV2-x(PO4)3 (x≥0.4) compositions exhibit 8–10% energy density gain in comparison to Na3V2(PO4)3 material, Na3.2Mn0.2V1.8(PO4)3 and Na3.4Mn0.4V1.6(PO4)3 are most preferable in terms of cycling stability.

High-entropy alloys: preparation, properties and practical application

In recent years, the unique physicomechanical properties of highentropy alloys (HEA) have been the subject of increased attention of Institute of Metallurgy, Ural Branch of RAS, Ekaterinburg, Russia researchers. The study of the thermodynamic characteristics of such materials may be of interest for formulating the principles of formation of structures with the necessary functional characteristics. Since the processes of structure and phase formation, as well as the diffusion mobility of atoms, the mechanism of formation of mechanical properties and thermal stability are significantly different from similar processes in traditional alloys, that is why HEA are allocated to a special group of materials. Of particular interest are high-entropy alloys based on transition refractory metals such as Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W. Light metals such as Ti, V, and Cr are usually selected to reduce the mass density; refractory ones such as Nb , Ta and W, are primarily responsible for the strength characteristics of the entire material. The paper provides a brief overview of results of the study of high-entropy alloys in the new laboratory of Institute of Metallurgy of UB RAS in 2019. Two groups of alloys were studied: HEA of the AlNbTiVZr type containing low-melting aluminum and HEA of the (Ti, V) ZrNbHf (Ta, W) type containing exclusively refractory transition metals. By varying the ratio of components in the first group of HEA, the existence limits of disordered regions of solid solution and intermetallic compounds characteristic of this system were established. For the second group of HEA, a forecast is made of the phase composition, properties and structure based on quantum-chemical calculations involving first-principle molecular dynamics. The forecast showed the possibility or unlikely formation of a disordered solid solution in the above systems with the presence or absence of specific chemical elements.

Structure – Reactivity - Relationship in Nanostructured and Amorphous Aluminium Lanthanoid Material Libraries

The lanthanoids are a consequent series of elements and with their 3 valence electrons they prefer the trivalent state while continuously filling the inner f-shell. A specific energetically stabilizing effect is observed so that the empty, the half-filled or the completely filled f-shell show extraordinary low energies resulting in a stabilizing effect so that neighboring valence states such as divalent or tetravalent can be also observed. Interestingly with increasing atomic number the atomic and ionic radii decrease - counter intuitively. As a result of the electronic shielding effect of the f-electrons the so-called lanthanoid contraction is observed.Aluminium is another element that forms preferentially trivalent ions. A combinatorial approach in which aluminium-lanthanoid-alloys are investigated both in terms of the alloy itself but in particular for the passivity based on the mixed oxides forming on these alloys is presented here. A complex attempt was made not only to cover the various elements themselves but also their concentration ratios in material thin film libraries. These material libraries are prepared in a large preparation and analysis cluster the so-called CALMAR. Asymmetrical physical codeposition of the constituting elements is used in HV and UHV chambers to prepare these libraries and to characterize them by a scanning EDX system as well as XRD.Theoretical considerations were used to compute the Pourbaix diagrams. Also phase diagrams of the Al-Lx alloys are consulted to identify intermetallics and regions of solid solution mixing.Passivation studies were performed using a flow type scanning droplet cell microscope FT-SDCM. This method allows the subsequent stepwise anodization and electrochemical impedance spectroscopy characterisation of a single spot of a library having a single composition. Spatial scanning of the library yields detailed information of the systematically changing alloy compositions. To understand not only the anodic oxide formation but also the chemical and electrochemical reactions during anodization a complementary investigation of the electrolyte is performed using inductively coupled plasma spectrometry.Various lanthanoids were mixed with aluminium and electrochemically studied. It is found that the large ionic radii mismatch is likely to cause strong amorphisation. In this way already binary alloys were found to form metallic glasses in some regions i.e. for some compositions. This has a strong impact on the passivation behavior and electrochemical stability. Some distinct intermetallic compounds in these binary alloys were found with the expected consequence for the stability.

Aging- and creep-resistance of a cast hypoeutectic Al-6.9Ce-9.3Mg (wt.%) alloy

A ternary Al-6.9Ce-9.3Mg (wt.%) hypoeutectic alloy, consisting of equal amounts of α-Al(Mg) solid-solution regions and Al(Mg)-Al11Ce3 eutectic colonies, is investigated in terms of its aging and creep resistance. The eutectic regions exhibit a microhardness of 1230 MPa, which is thrice the value of Al-Al11Ce3 eutectic regions in a binary Al-12.5Ce (wt.%) near-eutectic alloy, demonstrating that Mg in solid-solution enhances the strengthening provided by the micron-scale highly-branched Al11Ce3 phase. X-ray diffraction measurements during ambient-temperature tensile testing reveal that load is being transferred from the Al(Mg) matrix to the Al11Ce3 phase, confirming that the fine eutectic microstructure displays composite strengthening in addition to the expected precipitation- and solid-solution strengthening. The hardness remains effectively unchanged after aging at 450 °C for up to 8 weeks, indicating excellent coarsening resistance of the Al11Ce3 phase. The ternary alloy exhibits creep resistance at 300 °C slightly inferior to the near-fully eutectic binary Al-12.5Ce (wt.%) alloy, consistent with the presence of large regions of fast-creeping primary Al(Mg) solid-solution matrix between the strong Al(Mg)-Al11Ce3 eutectic colonies in the hypoeutectic ternary alloy.

Experimental and Theoretical Investigation on Phase Formation and Mechanical Properties in Cr-Co-Ni Alloys Processed Using a Novel Thin-Film Quenching Technique.

The Cr-Co-Ni system was studied by combining experimental and computational methods to investigate phase stability and mechanical properties. Thin-film materials libraries were prepared and quenched from high temperatures up to 700 °C using a novel quenching technique. It could be shown that a wide A1 solid solution region exists in the Cr-Co-Ni system. To validate the results obtained using thin-film materials libraries, bulk samples of selected compositions were prepared by arc melting, and the experimental data were additionally compared to results from DFT calculations. The computational results are in good agreement with the measured lattice parameters and elastic moduli. The lattice parameters increase with the addition of Co and Cr, with a more pronounced effect for the latter. The addition of ∼20 atom % Cr results in a similar hardening effect to that of the addition of ∼40 atom % Co.

Experimental Investigation of Phase Equilibria at 1200 °C in the Al-Nb-V System

Phase equilibria in the Al-Nb-V system are important data for the design of innovative Al-containing refractory-high-entropy alloys, however issues still open in this system. In the present work, Al-Nb-V phase equilibria at 1200 °C were re-investigated via microstructural characterization of heat-treated alloys using scanning electron microscopy, x-ray spectroscopy (EDS) and x-ray diffractometry. Results confirmed the existence of the three-phase fields BCC + Nb3Al + Nb2Al and BCC + Nb2Al + NbAl3 and the absence of ternary compounds. The solubility of binary phases Nb3Al and Nb2Al into the ternary and the stability region of the BCC solid solution were improved while the solubility of Nb in V5Al8 was confirmed negligible. In addition, VAl3 + NbAl3 diffusion couple were produced, confirming the miscibility gap between these phases and indicating the existence of NbAl3 + VAl3 + BCC equilibrium instead of NbAl3 + VAl3 + V5Al8.

Thermodynamic properties of solid solutions in the PbSe—AgSbSe2 system

The results of the study of the PbSe—AgSbSe2 system by measuring the emf of concentration chains with respect to PbSe in a temperature range of 300–450 K are presented. The formation in the system of a wide (37–100 mol.% AgSbSe2) region of solid solutions based on AgSbSe2 is shown. The partial thermodynamic functions of PbSe and lead in the alloys are calculated from the equations of the temperature dependences of the emf. The standard thermodynamic functions of formation and standard entropies of solid solutions (2PbSe)x(AgSbSe2)1−x (x = 0.4, 0.6, 0.8, and 0.9) are calculated by the integration of the Gibbs—Duhem equation over the PbSe—AgSbSe2 section using the literature data on the corresponding thermodynamic data for compounds PbSe and AgSbSe2.