Solid Solution Region Research Articles

Estimation of Sc3+ solubility in dodecahedral and octahedral sites in YSAG:Yb

AbstractA method for synthesizing YSAG:Yb optical ceramics has been developed. Additionally, the phase composition and unit cell parameters for YSAG, YbSAG, and their solid solutions have been determined. The limits of scandium solubility in the dodecahedral and octahedral sites of garnet crystal lattice have been estimated after annealing at 1600°C. The scandium solubility limit in the dodecahedral sites of YSAG:Yb was found to be 66 ± 2 at.%. The limit of scandium solubility in octahedral sites depended upon the type of garnet‐forming cations. The solubility limit for Sc3+ decreased from 97.5 ± 0.5 to 68.5 ± 1 at.% with simultaneous increase of ytterbium content in the YSAG‐YbSAG system. Therefore, the region of solid solutions existing with a garnet structure in the Al2O3–Sc2O3–Yb2O3–Y2O3 system was determined. Samples having scandium in both dodecahedral and octahedral sites, which had a Sc3+ content of ~30 at.%, were synthesized as a precursor for optical ceramic production.

Structure peculiarities of binary state diagrams of vanadium with neighboring elements of Mendeleev’s periodic table

Data on search for correlations between a structure of state diagrams of binary systems based on V-Me (Me = Ti, Zr, Hf, Nb, Ta, Cr, Mo, W) and crystal-geometric and crystal-chemical parameters were presented. Manifestation of both positive and negative deviations in experimental concentration dependences of the atomic volume in solid solutions in systems V-Me (Me = Ti, Nb, Ta, Cr, Mo) from Zen’s law was established. It was found that in the systems with unbounded regions of solid solutions, the deviation from Zen’s law is insignificant. A correlation was found between the types of state diagrams and the difference in atomic volumes of alloy-forming elements in systems V-Me (Me = Ti, Nb, Ta, Cr, Mo).

Crystal chemistry and phase equilibria of the CaO-½Dy2O3-CoOz system at 885 °C in air

The CaO-½Dy2O3-CoOz system prepared at 885 °C in air consists of two calcium cobaltate compounds. The 2D thermoelectric oxide, (Ca3-xDyx)Co4O9-z (0 ≤ x ≤ 0.6) 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 without the substitution of Dy on the Ca site. No solid solution of the distorted perovskite, (Dy1-xCax)CoO3-z was established at this temperature. In the CaO-Dy2O3 system, while a small solid solution region was identified for (Dy1-xCax)O(3-z)/2 (0 ≤ x ≤ 0.075), Dy was not present in the Ca site of CaO. Neither the reported Dy2CoO4 phase in the Dy2O-CoOz system nor the Ca-doped (Dy1+xCa1-x)CoO4-z phase was present at 885 °C. Three solid solution tie-line regions and four three-phase regions were determined in the CaO-½Dy2O3-CoOz system. A comparison of the phase diagrams in the CaO-½R2O3-CoOz (R = La, Gd and Dy) systems is presented.

Robust high-fidelity DFT study of the lithium-graphite phase diagram

Graphite is the most widely used and among the most widely-studied anode materials for lithium-ion batteries. With increasing demands on lithium batteries to operate at lower temperatures and higher currents, it is crucial to understand lithium intercalation in graphite due to issues associated with lithium plating. Lithium intercalation into graphite has been extensively studied theoretically using density functional theory (DFT) calculations, complemented by experimental studies through X-ray diffraction, spectroscopy, optical imaging and other techniques. In this work, we present a first principles based model using DFT calculations, employing the BEEF-vdW as the exchange correlation functional, and Ising model to determine the phase transformations and subsequently, the thermodynamic intercalation potential diagram. We explore a configurational phase space of about 1 billion structures by accurately determining the important interactions for the Ising model. The BEEF-vdW exchange correlation functional employed accurately captures a range of interactions including vdW, covalent and ionic interactions. We incorporate phonon contributions at finite temperatures and configurational entropy to get high accuracy in free energy and potentials. We utilize the built-in error estimation capabilities of the BEEF-vdW exchange correlation functional and to develop a methodological framework for determining the uncertainty associated with DFT calculated phase diagrams and intercalation potentials. The framework also determines the confidence of each predicted stable phase. The confidence value of a phase can help us to identify regions of solid solutions and phase transformations accurately.

Metastable Li1+δMn2O4 (0 ≤ δ ≤ 1) Spinel Phases Revealed by in Operando Neutron Diffraction and First-Principles Calculations

In this work, we examine the reaction mechanisms driven by the lithiation of Li1+δMn2O4 (0 ≤ δ ≤ 1) spinels via in operando neutron powder diffraction (NPD). New reaction mechanisms are proposed involving solid-solution regions within both cubic and tetragonal spinel phases in addition to a continuous phase transition between them. In operando NPD is an ideal tool to follow the light elements such as lithium and oxygen in cathode materials which are often the key to fully understand their structural evolutions. Here, we report a novel methodology to prepare an extremely thick electrode with ∼378 mg·cm–2 loading density suitable for the in operando NPD studies. Enabled by such thick electrode, we find that the metal oxygen M–O (M = Li and Mn) bond lengths in both end members LiMn2O4 and Li2Mn2O4 experience pronounced changes larger than dictated by the change in lattice parameters because of the locally formed Jahn–Teller distorted Mn3+. First-principles density functional theory calculations confirm these...

Combination Effect of Bulk Structure Change and Surface Rearrangement on the Electrochemical Kinetics of LiNi0.80Co0.15Al0.05O2 During Initial Charging Processes.

The correlations between bulk/surface structure change and electrochemical kinetics of LiNi0.80Co0.15Al0.05O2 are systematically investigated at atomic level, including the initial charged, half-charged, and over-charged states. In the initial stage of charge, surface rearrangement occurs and an amorphous Li2CO3 layer forms on the surface, which can release stress and provide a stable interface. The Li2CO3 surface layer decomposes upon charging, resulting in decreased interface resistance for charge transfer. Meanwhile, the bulk structure goes through the two-phase reaction region toward the solid solution region, which demonstrates higher electrical conductivity and faster Li-ion mobility. Along with the charging process, more substantial surface rearrangement and the decomposed Li2CO3 layer lead to surface degradation. Together with the anisotropic volume change-induced mechanical stress, microcracks stem from the surface and provide access for electrolyte penetration. All of these cause high kinetic barriers for Li-ion extraction, as demonstrated by the high interface and charge-transfer resistance and slow lithium diffusion in this region.

Enhancing Na+ Extraction Limit through High Voltage Activation of the NASICON-Type Na4MnV(PO4)3 Cathode

Sodium (de)intercalation in the Na4MnV(PO4)3 NASICON-type cathode has been studied with operando synchrotron X-ray powder diffraction and galvanostatic cycling up to 3.8 and 4.0 V cutoff voltages. Symmetry reduction from rhombohedral to monoclinic was observed immediately after the start of the electrochemical desodiation, with restoring of the rhombohedral phase at 3.8 V. Cycling within the 2.5–3.8 V potential range proceeds through both solid-solution and two-phase processes. An additional voltage plateau at ∼3.9 V is observed, associated with “unlocking” of the Na1 site in the rhombohedral phase. Reverse insertion of Na+ cations proceeds via the entire solid-solution region. The experimentally observed discharge capacity increases by ≈14% after raising cutoff voltage.

Combinatorial Thin Film Sputtering Au xAl1- x Alloys: Correlating Composition and Structure with Optical Properties.

The Au-Al alloy system was investigated via a combinatorial thin film sputtering method for its potential as a plasmonic material. Au xAl1- x combinatorial libraries were cosputtered from Au and Al elemental targets and the composition, phase, and dielectric function of a ∼350 nm film was determined using energy dispersive spectroscopy (EDS), grazing incidence X-ray diffraction (GIXRD), and spectroscopic ellipsometry, respectively. The phase evolution and optical properties were analyzed after annealing various compositions under a vacuum. The phases present matched the expected phases based on the published Al-Au binary phase diagram at all compositions. Interestingly, the mixed phase Al-AuAl2 region showed the most optical tunability, where a maximum in the real part of the dielectric function progressively shifted to higher energy for increasing gold concentration. For almost pure AuAl2, the imaginary component is largely reduced in the visible range and is comparable to that of pure Al in the UV region. A 20-nm-thick film with composition Au0.74Al0.26 was studied using a (scanning) transmission electron microscope with an in situ laser heating system. The structures of the as-deposited and laser annealed films were determined using selected area diffraction and the bulk plasmon of AuAl2 and Al realized with electron energy loss spectroscopy. Last, the Au-rich solid solution region was investigated as a surface enhanced Raman spectroscopy (SERS) substrate using the benezenethiol (BT) molecule. Good SERS intensity was maintained up to 30% Al addition where enhancements of 105 to 107 were still observed.

The effects of high pressure and superheating on the planar growth of Al3Ni phase in hypo-peritectic Al-30wt%Ni alloy

The constitutional undercooling criterion of the Al3Ni intermetallic compound with nil solubility was established, which reveals that there is no constitutional undercooling when the initial Al-Ni alloy concentration is lower than 43 wt%. Meanwhile, the interface stability growth criterion for the Al3Ni was also established by considering the effects of pressure and superheating on diffusion coefficient, interface growth rate, interface energy, and kinetic coefficient. The results demonstrate that when the pressure is greater than 4.2 GPa, the Al3Ni phase will move forward with a planar interface without superheating. Under the combined effects of high pressure and superheating the transition point of Al3Ni planar growth decreases. For example, with a superheat of 600 K, the pressure for stable planar growth decreases to 2.7 GPa. In addition, the microstructure of hypo-peritectic Al-30 wt%Ni alloy solidified at different conditions was investigated. It shows that the Al3Ni phase growth interface is unstable at 2 and 4 GPa with no superheating. The microstructure of the sample synthesized at 2 GPa with the superheat degree 600 K is typically hypereutectic microstructure. While the whole sample can be divided into there regions (high pressure solid solution region, mushy zone, and fully melted region which consists of planar growth single phase Al3Ni area and hypoeutectic zone) at 3 GPa/600 K.

(Y1–xBix)3(Fe1–yGay)5O12 Solid Solution Region in the Ieneke Diagram

Garnet ferrites with the overall composition (Y1–xBix)3(Fe1–yGay)5O12 (0 ≤ х ≤1, 0 ≤ y ≤1) have been synthesized and characterized by X-ray diffraction. A relationship has been demonstrated between an increase in the concentration of Ga3+ cations and an increase in Bi2O3 solubility in ss-Y3(Fe,Ga)5O12.

Structural Evolution and Microwave Dielectric Properties of xZn0.5Ti0.5NbO4-(1- x)Zn0.15Nb0.3Ti0.55O2 Ceramics.

Structure and microwave properties of xZn0.5Ti0.5NbO4-(1 - x)Zn0.15Nb0.3Ti0.55O2 ceramics in the range of x = 0.0-1.0 were investigated. Rietveld refinement analysis and Raman spectra show that rutile- and orthorhombic-type solid solutions formed at 0-0.2 and 0.65-1, a composite at 0.2-0.64. In the solid solution regions, chemical bonds are enlarged. In this case, the Zn/Ti/Nb-O1 bond covalency and bond susceptibility are reduced, and lattice energy and thermal expansion coefficient increase along with x increases, which is mainly responsible for the development of microwave dielectric properties. Furthermore, far-infrared spectra and a classical oscillator model were used to discuss the intrinsic dielectric properties in detail. Temperature stable ceramic was obtained for x = 0.516: εr ∼ 46.11, Q × f ∼ 27 031 GHz, and τf ∼ -1.51 ppm/°C, which is promising for microwave applications.

QUASITERNARY SYSTEM PbS–PbSе–Tl4PbSe3

Binary and complex chalcogenides of p-elements are perspective objects as a functional materials in the optics and thermoelectric technologies. To the investigation of the phisico-chemical interaction between them its devoted a considerable amount of work. That's why the study of new systems based on the known binary and ternary chalcogenides are actual.The initial compounds of the quasiternary PbS–PbSе–Tl4PbSe3 system had close lattice parameters (for PbS and PbSe compounds), similar structural motives ([PbS6(Se6)] octahedrons). Combination of structural similarity with high functional parameters determine the practicality of the investigation of the phase equilibria in the PbS–PbSе–Tl4PbSe3 system.The aim of the work is the study of the physico-chemical interaction system PbS–PbSе–Tl4PbSe3 determination of the coordinates of invariant points and monovariant lines courses, the homogeneity regions of the initial binary and ternary phases.Using the differential thermal (DTA) and X-ray diffraction (XRD) analyzes the pre-synthesized compounds Tl2Se, PbS, PbSе, Tl4PbSe3 were identified. Established that the obtained compounds are individual phases.Based on the results of the DTA, XRD and microstructural analysis (MSA) the physico-chemical interaction in the quasiternary system PbS–PbSе–Tl4PbSe3 were investigated. Established that in quasiternary system PbS–PbSе–Tl4PbSe3 at 573K exist two regions of solid solution based on Tl4PbSe3 and PbSхSe1-х (х=0–1) phases and one region of their co-crystallization. The widest range of homogeneity has a solid solution PbSхSe1-х (х=0–1) based on the initial binary lead chalcogenides. The PbSхSe1-х (х=0–1) solid solution occupies all section PbS–PbSe and extends to 10 mol. % into the system PbS–PbSе–Tl4PbSe3. The solid solution based on Tl4PbSe3 occupies the egde of the PbS–PbSе–Tl4PbSe3 concentration triangle. The width of the solid solution based on Tl4PbSe3 does not exceed 2 mol.% along the PbS–Tl4PbSe3 section and 7 mol.% in the PbSе–Tl4PbSe3.Based on the temperatures of the primary crystallization of alloys the projection of liquidus surface has been studied and built. Established that the fields of primary crystallization of Tl4PbSe3 and PbSхSe1-х (х=0–1) phases are divided by the line of monovariant eutectic equlibria e2–e1 (800–793K)

Na2Mn3+0.3Mn4+2.7O6.85: A cathode with simultaneous cationic and anionic redox in Na-ion battery

Here we report a high-capacity cathode, Na2Mn3+0.3Mn4+2.7O6.85, based on simultaneous cationic (Mn4+/Mn3+) and anionic (O2-/(O2)n-) redox process in Na-Mn-O system for Na-ion batteries (NIBs). An obvious voltage plateau at ~ 4.2 V vs. Na+/Na is reversibly presented during Na+ deinsertion/insertion demonstrated by XPS analysis of the participation of oxygen redox. This cathode delivers ~ 213 mA h g-1 in the voltage range of 1.5–4.5 V composed of two voltage plateaus from both cationic and anionic redox reaction. The two voltage plateaus exhibit the reversible phase transition upon Na+ insertion/deinsertion corresponding to a solid-solution region (high plateau) and a two-phase region (low plateau), respectively. The results indicate that anionic redox activity is available to develop high-capacity cathodes for NIBs.

Rotational motion of polyanion versus volume effect associated with ionic conductivity of several solid electrolytes

Volume effect has been extensively investigated in several families of solid electrolytes, i.e., expanding the skeleton lattice by bigger-size substitution favors the ionic conduction. However, this effect is not applicable in α-Li2SO4 and α-Na3PO4 based inorganic ionic plastic crystal electrolytes, a unique family of solid electrolytes. Here, it is proposed that the underlying rotational motion effect of polyanion, which is actually inhibited by the substitution of bigger-size polyanion in single-phase solid solution region and causes the unexpected lowering of the ionic conductivity instead, should need the more consideration. Furthermore, through utilizing the rotational motion effect of polyanion, it is given that a new explanation of the ionic conductivities of Li10MP2S12 (M = Si, Ge, Se) electrolytes deviating from the volume effect. These results inspire new vision of rationalization of the high-performance solid electrolytes by tuning the rotational motion effect of polyanion.

Efficient exploration of the High Entropy Alloy composition-phase space

High Entropy Alloys (HEAs), Multi-principal Component Alloys (MCA), or Compositionally Complex Alloys (CCAs) are alloys that contain multiple principal alloying elements. While many HEAs have been shown to have unique properties, their discovery has been largely done through costly and time-consuming trial-and-error approaches, with only an infinitesimally small fraction of the entire possible composition space having been explored. In this work, the exploration of the HEA composition space is framed as a Continuous Constraint Satisfaction Problem (CCSP) and solved using a novel Constraint Satisfaction Algorithm (CSA) for the rapid and robust exploration of alloy thermodynamic spaces. The algorithm is used to discover regions in the HEA Composition-Temperature space that satisfy desired phase constitution requirements. The algorithm is demonstrated against a new (TCHEA1) CALPHAD HEA thermodynamic database. The database is first validated by comparing phase stability predictions against experiments and then the CSA is deployed and tested against design tasks consisting of identifying not only single phase solid solution regions in ternary, quaternary and quinary composition spaces but also the identification of regions that are likely to yield precipitation-strengthened HEAs.

Thermodynamic Study of Cu2GeS3 and Cu2–xAg x GeS3 Solid Solutions by the EMF Method with a Cu4RbCl3I2 Solid Electrolyte

The Cu2GeS3–Ag2GeS3 system was studied by the EMF method with a Cu4RbCl3I2 solid electrolyte in the temperature range 300–380 K. The formation of wide regions of solid solutions from the starting compounds in this system was confirmed. The partial thermodynamic functions (ΔG, ΔH, ΔS) of copper in alloys were calculated from the equations of the temperature dependences of EMF. The current-forming reactions were determined based on the schematic diagram of solid-phase equilibria in the Cu–Ag–Ge–S system and used to calculate the standard thermodynamic functions of formation and the standard entropies of the compound Cu2GeS3 and solid solutions Cu2–xAg x GeS3 (х = 0.2, 0.4, 0.6, 1.6, and 1.8) and the thermodynamic functions of mixing of the latter from ternary compounds.

Phase Diagram of the System Tl2Te–Tl5Te3–Tl9GdTe6

The ternary system Tl–Gd–Te within the composition range Tl2Te–Tl5Te3–Tl9GdTe6 was studied by a set of physicochemical analysis methods. Some internal polythermal sections and the isothermal section at 300 K of the phase diagram were built, projections of the liquidus and solidus surfaces were constructed, and the graphs of the concentration dependences of the parameters and microhardness were plotted. It was shown that much (more than 90%) of the area of the concentration triangle is occupied by the homogeneity region of solid solutions with the Tl5Te3 structure (δ-phase). Solid solutions based on Tl2Te (α-phase) form within a narrow region. The regions of the α- and δ-phases are separated by two-phase region α + δ.

The Sections GeSnSb4Te8–GeTe and GeSnSb4Te8–SnTe of the Quasi-Ternary System GeTe–Sb2Te3–SnTe

By differential thermal, X-ray powder diffraction, and microstructural analyses and microhardness and density measurements, phase equilibria in the sections GeSnSb4Te8–GeTe and GeSnSb4Te8–SnTe were studied and their state diagrams were constructed. It was determined that these sections are quasi-binary sections of the eutectic type of the GeTe–Sb2Te3–SnTe system. The coordinates of the eutectic points in the sections GeSnSb4Te8–GeTe and GeSnSb4Te8–SnTe are (40 mol % GeTe, 700 K) and (30 mol % SnTe, 750 K), respectively. Regions of solid solutions based on the initial components in the sections were identified. Alloys in the regions of solid solutions are p-type semiconductors.

Thermodynamic Study of the 2PbTe–AgSbTe2 System Using EMF Technique with the Ag4RbI5 Solid Electrolyte

The work presents the results of studies of the 2PbTe–AgSbTe2 system using the EMF technique with the Ag4RbI5 solid electrolyte in the temperature range of 300–430 K. Formation of a wide (0–80 mol % AgSbTe2) region of PbTe-based solid solutions in the system is shown. Partial thermodynamic functions $$\left( {\overline {\Delta G} ,\overline {\Delta H} ,\overline {\Delta S} } \right)$$ of alloyed silver are calculated on the basis of the equations of the temperature dependences of EMF. Potential-forming reactions are determined on the basis of the data on solid-phase equilibriums in the Ag2Te–PbTe–Sb2Te3–Te system that are used to calculate standard thermodynamic functions of formation and standard entropies of (2PbTe) x (AgSbTe2)1–x (x = 0.2; 0.4; 0.6; 08; 0.9) solid solutions.

Structure feature of ternary state diagrams of Cr-Ti-V and Cr-Mn-V systems

This paper presents the research results of features of structural and phase states in Cr-Ti-V and Cr-Mn-V systems based on analysis of crystal-geometric and crystal-chemical factors. The diagrams of isothermal sections of state diagrams of Cr-Ti-V and Cr-Mn-V systems were built in coordinates of the electron number (s+d) per atom with homogeneity regions of solid solutions and intermetallic compounds. It was shown that in the Cr-Ti-V system, addition of Mn atoms leads to substantial extension of the existence domain of the disordered solid solution based on the BCC lattice.