Anion Positions Research Articles

Membrane transport of rare earth metal ions N, N’-bisdioctylphosphorylmethyl-1,4-diaminobutane by the active transport mechanism

The method of membrane extraction for rare earth elements (REE) using the carrier N, N’-bisdioctylphosphorylmethyl-1,4-diaminobutane (DPDA-8) ions, leveraging an active transport mechanism, has been optimized. The distribution of DPDA-8 within the membrane pores was confirmed using scanning electron microscopy (SEM). Both light and heavy REE extractions from a simulated solution using DPDA-8 and trioctylphosphine oxide (TOPO) in 1,2-dichlorobenzene were explored. The influence of feed solution pH, carrier and anion concentration, supported liquid membrane (SLM) type and stability, and cell temperature, among other parameters, were meticulously examined. The results indicate a decrease in permeability with a decrease in feed solution pH attributed to competitive acid transport through the membrane. Additionally, the formation of H-complexes between carriers and perchloric or phosphoric acids was investigated using Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction (XRD) techniques. Changes in the stretching bands of amino and phosphine oxide groups in DPDA-8 were monitored and characterized. XRD analysis of the crystal structures of salts DPDA-6·ClO4 and DPDA-12·H2PO4 revealed a two-dimensional layered supramolecular organization with varying anion positions relative to hydrophobic fragments. The DPDA-8 carrier demonstrated significantly higher permeability values compared to TOPO, with differences in permeability exceeding twofold for certain metals. FTIR spectroscopy identified the main coordination centers of DPDA-8 during the liquid–liquid extraction of specific REEs.

The structural, electronic and magnetic properties of [formula omitted] anti-perovskite

A comprehensive exploration of the structural, electronic, and magnetic attributes of anti-perovskite Fe3ZnC carbides was carried out using Density Functional Theory (DFT) and Monte Carlo Simulation (MCS). These anti-perovskite materials possess a unique structure where cation and anion positions are interchanged within the perovskite framework. Our study involves a comparative analysis of the electronic band structures and density of states (DOS) for Fe3ZnC, considering prior theoretical and experimental research. Understanding these anti-perovskite materials' band structures and DOS is pivotal for their effective utilization in magnetic sensors and magnetic refrigeration applications. Our results indicate that Fe3ZnC displays ferromagnetic metallic behavior, particularly when applying the Generalized Gradient Approximation (GGA). Notably, there is a significant overlap between the valence (VB) and conduction (CB) bands. Furthermore, MCS predicts a second-order ferromagnetic-to-paramagnetic transition in the anti-perovskite Fe3ZnC compound, characterized by a notably high Curie temperature. These insights advance our understanding of these materials, paving the way for their effective utilization in magnetic technologies.

Aromatic salt induced modulations in micellization behavior of amide functionalized surface-active ionic liquids: The role of cationic head group

The present study highlights the effect of aromatic salt i.e. sodium benzoate (NaBz) at fix concentration (1 mM), on the micellization behavior of four amide functionalized surface-active ionic liquids (SAILs) having different cationic head groups in aqueous medium. The adsorption behavior of the SAILs at the air-solution interface has been investigated by tensiometry, where improved surface activity was observed in all the investigated SAILs in the presence of added hydrotrope. The conductivity, steady-state fluorescence, dynamic light scattering (DLS), and zeta-potential measurements have been performed to probe the micellization of the SAILs in bulk solution. The position and orientation of aromatic anion, Bz-, at the micelle-water interface surface has been investigated by 1H NMR spectroscopy. The thermodynamic aspects of micellization have been examined by Isothermal titration calorimetry (ITC). It has been observed that the nature, geometry, and steric factor of the cationic head group of SAILs govern their interactions with Bz- and this influences the characteristic properties of micellization.

Microstructure and properties of forsterite-zirconia composite ceramics for solar thermal storage

Solar thermal power generation is an important direction of energy utilization, and thermal storage materials are the key to ensure the continuous use of energy. In this paper, forsterite - zirconia composite ceramics were prepared by adding different contents of 3Y–ZrO2 and their physical properties, phase composition, microstructure thermal shock resistance and thermal physical properties were studied. The results showed that the water absorption, bulk density and bending strength of sample A3 sintered at 1600 °C (59.10 wt% fused magnesia, 40.90 wt% quartz and 30 wt% 3Y–ZrO2) were 0.35 %, 3.27 g/cm3 and 83.66 MPa, respectively. The crystal phase of sample A3 was forsterite and c-ZrO2. Mg2+ and Y3+ replace Zr4+, formed oxygen vacancy in the anion position, distort the coordination layer and release some interlayer stress to promote the stability of c-ZrO2. In the sintering process, the zirconia solid solution existed in the form of second phase, which reduced the growth rate of periclase, facilitated the pore discharge in the sample and promotes sintering. The thermal conductivity of forsterite - zirconia composite ceramics at room temperature was 5.52 W/(m·K). At 1000 °C, the specific heat capacity and heat storage density were 1.09 J/(g·K) and 1062.36 kJ/kg, respectively. The forsterite - zirconia composite ceramic prepared in this study was suitable for high temperature environment, its heat storage capacity was excellent, and it was suitable for high temperature heat storage system.

Ionic strength and phase systems influence nanotubular material functionality

We synthesized novel thiacyanine chromonic liquid crystals (CLCs) and structurally characterized using NMR and mass spectrometry. The impact of distinct substitution at the para position of aromatic counter anions, aliphatic counter ion chain length, and varied spacer parity of thiacyanine dyes on CLC formation is investigated. Liquid crystal properties of the synthesized dyes are characterized by polarizing optical microscopy (POM) and X-ray diffraction (XRD) studies. Dyes exhibit nematic (N), lamellar (Lα), columnar rectangular (Colr), and columnar oblique (Colob) CLCs at different concentrations in the water. Electronic absorption spectra reveal Scheibe aggregation in all the dyes. Cylicvoltametry studies confirm redox behaviour in TC-1a and TC-5e dyes. Chromonic LCs hybrid nano-materials are synthesized using sol–gel method. Scanning electron microscopy employed to confirm nano tubular fiber structure of the hybrid nanomaterilals..

Single crystal polarization-orientation Raman spectroscopy of zeolite LTA with confined S3− anions - High dielectric constant nanoporous material

We apply polarization-orientation Raman spectroscopy, as an alternative to X-ray diffraction, to LTA single crystals containing S3− in sodalite cages additionally to S8 rings in large cavities. The sample was obtained via sulfur vapor adsorption at ∼550 °C (LTA-S-550). We show that S3− is located in the (110) plane with its 2-fold axis along the LTA 4-fold axis. The anion position suggests strong interaction of its terminal atoms with Na+ localized in LTA 6-membered rings. The anions display optical absorption band at ∼590 nm (2.1 eV) and resonant Raman enhancement. We observe a record-high S3− bond-bending mode frequency ∼274 cm−1 due to a strong bond-angle contraction. This leads to the Fermi resonance of its overtone with the symmetric bond-stretching mode in the frequency range of 544–552 cm−1. An anomalous Raman downshift of the S3− bond-stretching modes with a decrease of temperature is observed and attributed to partial compressive stress relaxation. Luminescence band at ∼845 nm is observed suggesting considering LTA-S-550 as an interesting light-emitting material. We discuss a role of S3− in the high dielectric constant up to ∼160 and a possible contribution of the anion to the ion-exchange selectivity to Sr2+/Cs+ enhancements of LTA with sulfur.

TO A QUESTION OF SULFUR SITES IN CRYSTAL STRUCTURES OF TETRAHEDRITE GROUP MINERALS: RELATIONSHIPS BETWEEN OCCUPANCY, EFFECTIVE ION SIZES, AND UNIT CELL PARAMETERS

In this work, a crystal chemical analysis of the known experimentally deciphered crystal structures of tetrahedrite group minerals was carried out in order to reveal the relationships between the occupancies of anion crystallographic sites in the structures, their effective sizes and unit cell parameters. To achieve this aim, we analyzed the effective sizes of the 24g and 2a anion sites in 68 deciphered crystal structures of tetrahedrite group minerals according to the published data. The analysis was carried out using the TOPOSPro software package by partitioning the space into Voronoi–Dirichlet polyhedra (VDP). It has been shown theoretically for the first time that the content of a large sulfur ion and its deficiency affect the unit cell parameter. A linear correlation between the VDP volume of the anionic site of S2– (24g) and the unit cell parameter in minerals of the tetrahedrite group was established, which shows that the anionic substructure dictates the structural motif in this class of compounds. It was found that the change in the VDP volumes of sulfur anions is associated with different occupancies of anionic sites. It is found that the formula (unit cell) of the compound contains fewer than 13 sulfur ions in almost all deciphered crystal structures of tetrahedrite group minerals. It was concluded that the calculated VDP volume of the 24g anionic position less than 22 Å3 indicates a significant deficit in the anionic substructure. It was shown that, using information about the VDP volumes of all anionic and cationic sites in the structure, it is possible to predict the unit cell parameters of minerals of the tetrahedrite group with an accuracy of 0.01 Å

Influence of synthesis temperature on oxygen exchange behavior of electrode material PrBaFe2O6−δ

PrBaFe2O6−δ attracts attention as a promising material for electrode development for solid oxide fuel cells. A comparative study of the structure, oxygen non-stoichiometry, and high-temperature defect chemistry in PrBaFe2O6−δ prepared at 1000 °C, hereinafter referred to as LTS (low temperature synthesis) and at 1350 °C, hereinafter referred to as HTS, was carried out. Experimental data were obtained by X-ray and electron diffraction, thermogravimetry, and coulometric titration. The onset temperature of oxygen exchange with the gas phase was found to be 278 °C and 484 °C for the LTS and HTS oxides, respectively. The revealed advantage of the LTS oxide is argued to be conditioned by the structural features. Although X-ray diffraction identified the structure of both oxides as cubic perovskite with Pm3¯m space group, electron diffraction found in the LTS oxide the incomplete formation of an ordered superstructure with a Cmmm space group, in contrast to only the short-range ordering in the HTS oxide. The modeling of defect chemistry at 750–950°С indicates a uniform distribution of oxygen ions over the available anion positions with close thermodynamic parameters of the defect formation reactions for both oxides. These results, however, can reflect only a peculiarity of the LTS oxide state with disordered anion sublattice at high temperature and does not mean unambiguous independence of oxygen exchange behavior on thermodynamic parameters of the oxidation reaction.

High-Pressure and High-Temperature Dion-Jacobson Layered Perovskite Polymorphs of KWO3 F.

Two new Dion-Jacobson layered perovskite polymorphs of the known oxyfluoride compound KWO3 F are reported. A high-pressure modification was synthesized using a multianvil setup and subsequently transformed into a high-temperature phase at ∼311 °C. The crystal structures of both polymorphs were determined by use of single-crystal X-ray diffraction and are described in detail herein. Differential thermal analyses and thermogravimetric analyses were carried out to further investigate the phase transition characteristics. Bond valence (BV) and charge distribution (CHARDI) calculations confirm the occupancy of mixed O|F anion positions, and Rietveld refinements as well as MAPLE calculations support the structure models.

Mixed Organic Halide Perovskite Energy Harvester for Solar Cells

Organic- inorganic hybrid perovskite shows promising properties such as optical, electrical, and magnetic. To address issues in the standard methylammonium lead iodide perovskite such as toxicity and stability, lead was replaced with Cu in metal ion part and iodine replaced by chlorine in the anionic position. In this work, methyl ammonium copper chloride (MA2CuCl4) and phenyl ethyl ammonium copper chloride (PEA2CuCl4) were synthesised. Optical and structural property variations of solution obtained by mixing MA2CuCl4 and PEA2CuCl4 in 1:1 ratio was studied. Methylammonium lead iodide has a wide range of applications, particularly in solar cells and photovoltaic systems. Phenylethyl ammonium copper chloride material exhibits both ferroelectric and ferromagnetic properties. Methylammonium copper chloride is hygroscopic and unstable. To increase the stability of the material the organic part can be replaced with higher-order functional groups. Phenylethyl ammonium copper chloride is found to be thermally stable and has more moisture resistance ability compared to methyl ammonium copper chloride. From angle of efficiency, methyl ammonium copper chloride possessed higher performance than phenylethyl ammonium copper chloride, particularly in the field of solar cell perovskites. Uv-vis spectroscopy, FE-SEM, XRD, FTIR characterizations were done.

Crystal Structure, Characterization, and Luminescence Properties of Mn4+‐Doped K3Nb2O4F5

AbstractIn this paper, we present the high‐pressure/high‐temperature synthesis and characterization of the potassium fluoridooxidoniobate K3Nb2O4F5. Single‐crystal analysis revealed that the phase crystallizes in the trigonal space group m (hR18) with a=5.799(2), c=21.371(4) Å, V=622.4(4) Å3 and Z=3 at T=299 K exhibiting a structure type closely related to that of Ba2RbFe2F9. The assignment of the anion positions to oxygen and fluorine is based on crystallographic data and BLBS/CHARDI calculations. Further characterization via EDX spectroscopy was carried out, corroborating the ratio of K to Nb. Doping of the title compound with Mn4+ was achieved in a secondary step using a ball‐mill, resulting in a red phosphor material, which was additionally analyzed by luminescence spectroscopy. The emission maximum is located at λmax=630 nm.

Limitations of non-polarizable force fields in describing anion binding poses in non-polar synthetic hosts.

Transmembrane anion transport by synthetic ionophores has received increasing interest not only because of its relevance for understanding endogenous anion transport, but also because of potential implications for therapeutic routes in disease states where chloride transport is impaired. Computational studies can shed light on the binding recognition process and can deepen our mechanistic understanding of them. However, the ability of molecular mechanics methods to properly capture solvation and binding properties of anions is known to be challenging. Consequently, polarizable models have been suggested to improve the accuracy of such calculations. In this study, we calculate binding free energies for different anions to the synthetic ionophore, biotin[6]uril hexamethyl ester in acetonitrile and to biotin[6]uril hexaacid in water by employing non-polarizable and polarizable force fields. Anion binding shows strong solvent dependency consistent with experimental studies. In water, the binding strengths are iodide > bromide > chloride, and reversed in acetonitrile. These trends are well captured by both classes of force fields. However, the free energy profiles obtained from potential of mean force calculations and preferred binding positions of anions depend on the treatment of electrostatics. Results from simulations using the AMOEBA force-field, which recapitulate the observed binding positions, suggest strong effects from multipoles dominate with a smaller contribution from polarization. The oxidation status of the macrocycle was also found to influence anion recognition in water. Overall, these results have implications for the understanding of anion host interactions not just in synthetic ionophores, but also in narrow cavities of biological ion channels.

On the anion and cation positions within and nearby R(101¯2)$R(10\overline{1}2)$, Σ(202¯4)$\mathrm{\Sigma}(20\overline{2}4)$, and Π(101¯4)$\mathrm{\Pi}(10\overline{1}4)$ planes of α‐Al2O3 corundum structure

AbstractThe positions of aluminum cations and oxygen anions within and nearby the , , , and planes of α‐Al2O3 corundum structure are determined and compared with the corresponding ion positions within and nearby their conjugate‐adjacent planes , , , and planes. The plane contains neither aluminum nor oxygen ions, while the planes , , and contain only oxygen anions, whose planar densities are and . The planes , , and contain only aluminum cations with planar densities and . The plane contains both aluminum and oxygen ions, whose planar densities are and . The nearest ions to the , , , and planes are at a normal distance of 0.58 Å from these planes, which is one‐half of the normal distance between the adjacent R and , or r and planes. The ions nearest to the and planes are also at a normal distance of 0.58 Å from these planes. The nearest ions to the and planes are 0.85 Å from these planes, which is one‐half the interplanar spacing between the adjacent Π or π planes. The obtained results are of interest for the evaluation of ionic bonding and surface energies, epitaxial film growth over differently oriented sapphire substrates, and for the analysis of plastic deformation and cleavage fracture of sapphire crystals under different loading and temperature conditions.

Enhanced thermoelectric performance in n-type Mg3.2Sb1.5Bi0.5 doping with lanthanides at the Mg site

• Gd and Ho have increased the DOS of the valence band near the Fermi level, and the d electrons of Gd and Ho have made extraordinary contributions. • Gd and Ho are effective n-type cation site dopants with higher doping efficiency and better carrier concentration than the anion site dopants chalcogenide elements. • For Mg 3.2 Gd 0.02 Sb 1.5 Bi 0.5 and Mg 3.2 Ho 0.02 Sb 1.5 Bi 0.5 samples, we obtain high zT values of 1.61 and 1.55 at 725 K, respectively. • Gd as well as Ho are an alternative effective n-type doping element for higher thermoelectric performance. Mg-based thermoelectric materials have attracted more and more attention because of their rich composition elements, green environmental protection, and lower price. In recent years, the thermoelectric properties of n-type Mg 3 Sb 2 materials have been optimized by doping chalcogenide elements (S, Se, and Te) at the anionic position. In this work, n-type Mg 3.2 A x Sb 1.5 Bi 0.5 ( A = Gd, Ho; x = 0.01, 0.02, 0.03, and 0.4) samples were prepared by the cation site doping of lanthanide elements (Gd and Ho). The research results show that Gd and Ho doped n-type Mg 3.2 Sb 1.5 Bi 0.5 samples are entirely comparable to the S, Se, and Te doped n-type Mg 3.2 Sb 1.5 Bi 0.5 samples, demonstrating more excellent thermoelectric properties. Doping with lanthanides (Gd and Ho) at the Mg site increases the carrier concentration of the material to 8.161 × 10 19 cm −3 . Doping induces the contribution of more electron, thus obtaining higher conductivity. The maximum zT value of the Mg 3.2 Gd 0.02 Sb 1.5 Bi 0.5 and the Mg 3.2 Ho 0.02 Sb 1.5 Bi 0.5 samples reaches 1.61 and 1.55, respectively. This work theoretically and experimentally demonstrates Gd and Ho are efficient n-type dopants for Mg 3.2 Sb 1.5 Bi 0.5 thermoelectric material.

Rock-Salt-Ordered Nitrohalide Double Antiperovskites: Theoretical Design and Experimental Verification

Motivated by the success of metal halide perovskites in the field of optoelectronics, antiperovskites, which have the same crystal lattice as that of perovskites but with switched anion and cation positions, have recently been considered as potential candidates for optoelectronic applications. However, the best-known oxyhalide antiperovskites A3OX (A = alkali metal; X = halogen) generally exhibit very large bandgaps due to their immensely strong ionicity. In this work, we report the theoretical design and experimental verification of rock-salt-ordered double antiperovskites with reduced bandgaps. Each of two O anions in the A3OX oxyhalide antiperovskites is replaced with the combination of a trivalent N anion and a monovalent Y″ anion, yielding A6NY″X2 double antiperovskites. Density functional theory (DFT) calculations reveal that compared with the A3OX antiperovskites, the A6NY″X2 double antiperovskites have significantly reduced bandgaps, mainly due to high-lying N 2p orbitals. On the other hand, the p orbitals of the Y″ anion lie far below the N 2p orbitals and almost do not affect the bandgaps. Guided by the DFT calculations, we successfully synthesized four nitrohalide double antiperovskites, that is, Li6NBrBr2, Li6NII2, Li6NClBr2, and Li6NBrI2, and verified the predicted bandgap reductions. Our work provides strategies for designing double antiperovskites and expands the large family of antiperovskites.

Theoretical design of Na-rich anti-perovskite as solid electrolyte: The effect of cluster anion in stability and ionic conductivity

The next-generation solid-state batteries need safe and efficient solid-state electrolytes. However, the conventional solid-state electrolytes materials often suffer from low ionic conductivity. The emerging anti-perovskites are potential solid electrolytes materials for their rich cations and tunable crystal structure. Here, the first-principles density functional theory (DFT) calculations are employed to investigate the stability, electronic properties, elastic constants and the ions migration of sodium-rich anti-perovskite Na3SA (A ​= ​AlF4¯, ClO4¯, ICl4¯, IO4¯). Calculations show that the clusters substitution at anion position A of Na3SA displays larger band gap and faster Na ion transport than that of halogen anions (e.g., Cl, Br, I). Among them, the band gaps of Na3SAlF4 and Na3SClO4 exceed 3.5 ​eV, which indicates their excellent electrochemical stability. The AlF4¯ cluster exhibits high sodium ion conductivity (6.55 ​× ​10-2 ​S ​cm-1), low activation energy (0.19 ​eV) and small migration barrier (0.46 ​eV) according to the ab initio molecular dynamics (AIMD) simulations and transition states study. Molecular dynamics simulations suggest that the enhanced ionic conductivity is due to the rotation of cluster ions which promotes the migration of sodium ions; moreover, the large volume created by anion clusters leads to larger lattices which is also benefit for fast ion transport. Therefore, this work designs Na-rich anti-perovskite with high ionic conductivity by substitution of anion clusters and also provides the Na ion transport mechanism for reference in solid-state electrolytes.

Structures of Ca5(VO4)3Cl and Ca4.78(1)Na0.22(PO4)3Cl0.78: positions of channel anions and repulsion on the anion in apatite-type compounds

Single crystal specimens of apatite-type compounds Ca5(VO4)3Cl and Ca4.78 (1)Na0.22(PO4)3Cl0.78 were prepared with a flux-growth technique and their structures were examined with single-crystal X-ray diffraction. The anion channel is defined by a face-sharing array of nearly regular Ca octahedra, which run along c, together with flat O3 trigonal antiprisms that are concentric with the Ca octahedra and highly oblate in [001]. The position of the channel anion in Ca5(VO4)3Cl is split into two at [0, 0, ±0.1691 (6)] with half occupancies. Dynamic disorder among these two positions is suggested from a saddle-shaped electron density distribution through the Ca regular triangle, i.e. the shared face of the Ca octahedra at z = ¼. The position of Cl− was too close to Ca2+ under bond-valence consideration. This is due to repulsion on Cl− from the flat O3 trigonal antiprism which is located at z = 0, namely, in between pairs of split Cl site positions. Ca4.78 (1)Na0.22(PO4)3Cl0.78 crystallizes as a disordered hexagonal structure in which the crystallographic pattern is not an intermediate state but a projection of two distinct halves of the monoclinic pattern [doubled in b; Mackie, Elliot & Young (1972). Acta Cryst. B28, 1840–1848] in one hexagonal cell. In spite of quite different environments, the bond-valence sums for Cl− in these structures are large and similar to each other. The repulsion between O2− and Cl− and a demand for keeping Ca2+ and Cl− apart are balanced at the positions where bond-valence sums for Cl− are around 1.2.

Structural Features and Defect Equilibrium in Cubic PrBa1-xSrxFe2O6-δ.

The structure, oxygen non-stoichiometry, and defect equilibrium in perovskite-type PrBa1−xSrxFe2O6−δ (x = 0, 0.25, 0.50) synthesized at 1350 °C were studied. For all compositions, X-ray diffraction testifies to the formation of a cubic structure (S.G. ), but an electron diffraction study reveals additional diffuse satellites around each Bragg spot, indicating the primary incommensurate modulation with wave vectors about ±0.43. The results were interpreted as a sign of the short-order in both A-cation and anion sublattices in the areas of a few nanometers in size, and of an intermediate state before the formation of an ordered superstructure. An increase in oxygen deficiency was found to promote the ordering, whereas partial substitution of barium by strontium caused the opposite effect. The oxygen content in oxides as a function of oxygen partial pressure and temperature was measured by coulometric titration, and the data were used for the modeling of defect equilibrium in oxides. The simulation results implied oxygen vacancy ordering in PrBa1−xSrxFe2O6−δ that is in agreement with the electron diffraction study. Besides oxidation and charge disproportionation reactions, the reactions of oxygen vacancy distribution between non-equivalent anion positions, and their trapping in clusters with Pr3+ ions were taken into account by the model. It was demonstrated that an increase in the strontium content in Pr0.5Ba0.5−xSrxFeO3−δ suppressed ordering of oxygen vacancies, increased the binding energy of oxygen ions in the oxides, and resulted in an increase in the concentration of p-type carriers.

THE SbBiTe2Se-SbBiTe2S PHASE DIAGRAM OF THE Sb-Bi-S-Se-Te SYSTEM

Using powder X-ray diffraction (PXRD) and differential thermal analysis (DTA), the phase equilibria of the SbBiTe2Se – SbBiTe2S section were studied, and its T-x diagram was constructed. The system is non-quasibinary, due to both initial phases melting in the temperature range. The system is stable below the solidus, which is characterized by the formation of continuous solid solutions (α-phase) with a tetradymite-like hexagonal structure. An analysis of the structural features of tetradymite and other tetradymite-like compounds shows that the substitution of atoms by related atoms is possible in all layers of the packet. In this work sulfur atoms in the central layer can be easily replaced by selenium atoms. This tendency allows us to expect the formation of the range of compositions in the BiSb-Te-Se-S system in which substitutions are realized in cationic and anionic positions. Lattice parameters were determined from the results of powder diffraction patterns. It has been established that the crystal lattice parameters of solid solutions change linearly with composition, which complies with the Vegards rule. Keywords: SbBiTe2Se – SbBiTe2S system, phase diagram, tetradymite-like structure, solid solutions, high entropy alloys.

THE SbBiTe2Se-SbBiTe2S PHASE DIAGRAM OF THE Sb-Bi-S-Se-Te SYSTEM

Using powder X-ray diffraction (PXRD) and differential thermal analysis (DTA), the phase equilibria of the SbBiTe2Se – SbBiTe2S section were studied, and its T-x diagram was constructed. The system is non-quasibinary, due to both initial phases melting in the temperature range. The system is stable below the solidus, which is characterized by the formation of continuous solid solutions (α-phase) with a tetradymite-like hexagonal structure. An analysis of the structural features of tetradymite and other tetradymite-like compounds shows that the substitution of atoms by related atoms is possible in all layers of the packet. In this work sulfur atoms in the central layer can be easily replaced by selenium atoms. This tendency allows us to expect the formation of the range of compositions in the BiSb-Te-Se-S system in which substitutions are realized in cationic and anionic positions. Lattice parameters were determined from the results of powder diffraction patterns. It has been established that the crystal lattice parameters of solid solutions change linearly with composition, which complies with the Vegards rule. Keywords: SbBiTe2Se – SbBiTe2S system, phase diagram, tetradymite-like structure, solid solutions, high entropy alloys.