Sc<Subscript>2</Subscript>S<Subscript>3</Subscript>–Cu<Subscript>2</Subscript>S phase diagram

A phase diagram is constructed for the Sc₂S₃–Cu₂S system. The system forms two incongruently melting complex sulfides: hexagonal CuScS₂ (1Cu₂S: 1Sc₂S₃): a = 0.3734 nm, c = 0.6102 nm, space group P3m1, Т_m = 1635 K, ΔH_m = 1670 kJ/mol; and cubic CuSc₃S₅ (1Cu₂S: 3Sc₂S₃), a = 1.0481 nm, space group Fd3m, Т_m = 1835 K. In the 45–62 mol % Cu2S solid solution (ss) range, there is a singular point corresponding to the composition of compound CuScS₂ (50 mol % Cu₂S). The Sc₂S₃-based solubility at 1070 K is 14 mol % Cu₂S. In the γ-Cu₂S-based solid solution range, there is a peritectic point at 7 mol % Sc₂S₃, 1423 K.     

Phase equilibria in the Cu<Subscript>2</Subscript>S–La<Subscript>2</Subscript>S<Subscript>3</Subscript>–EuS system

Phase equilibria in the isothermal (970 K) and polythermal LaCuS₂–EuS, Cu₂S–EuLaCuS₃, LaCuS₂–EuLa₂S₄, and EuLaCuS₃–EuLa₂S₄ sections of the Cu₂S–La₂S₃–EuS system have been studied. EuLaCuS₃ (annealing at 1170 K) is of orthorhombic system, space group Pnma, a = 8.1366(1) Å, b = 4.0586(1) Å, c = 15.9822(2) Å, is isostructural to Ba₂MnS₃, and incongruently melts by the reaction EuLaCuS_3cryst (0.50 EuS; 0.50 LaCuS₂) ? 0.22 EuS SS (0.89 EuS; 0.11 LaCuS₂) + 0.78 liq (0.39 EuS; 0.61 LaCuS₂); ΔН = 52 J/g. The Cu₂S–La₂S3–EuS system has been found to contain five major subordinate triangles. At 970 K, tie-lines lie between EuLaCuS₃ and the Cu₂S, EuS, LaCuS₂, and EuLa₂S₄ phases and between the LaCuS₂ phase and the γ-La₂S₃–EuLa2S4 solid solution. Eutectics are formed between LaCuS₂ and EuLaCuS₃ at 26.0 mol % of EuS and T = 1373 K and between EuLaCuS3 and EuLa₂S₄ at 29.0 mol % of EuLa₂S₄ and T = 1533 K.     

Phase Equilibria in Systems DyCuS<Subscript>2</Subscript>–EuS and Cu<Subscript>2</Subscript>S−Dy<Subscript>2</Subscript>S<Subscript>3</Subscript>−EuS

The phase diagram of system DyCuS₂–EuS has been first constructed, and the phase equilibria in the Cu₂S–Dy₂S₃–EuS triangle at 970 K have been studied. Compound EuDyCuS₃ (1DyCuS₂ : 1EuS), space group Pnma, a = 10.1901(3) Å, b = 3.9270(1) Å, c = 12.8468(3) Å, melts incongruently at 1727 ± 7 K according to the reaction: EuDyCuS_3solid ? 0.17 SS EuS (90 mol % EuS, 10 mol % DyCuS₂) + 0.83 liq (42 mol % EuS, 58 mol % DyCuS₂), ΔH = 2.9 ± 0.6 kJ/mol; microhardness of the phase is 3080 ± 35 MPa. Compound EuDyCuS₃ is transparent in the range 3000–1800 cm^–1. In system DyCuS₂–EuS, the solid solution (SS) based on EuS extends from 91 to 100 mol % at 1770 K and from 92 to 100 mol % at 1170 K. In γ-DyCuS₂, 2 mol % EuS dissolves at 1487 K. The eutectic is formed between compounds DyCuS₂ and EuDyCuS3 at 12 mol % EuS, T = 1487 ± 8 K. In system Cu₂S?Dy₂S₃?EuS, 10 secondary systems have been isolated. At 970 K, tie-lines are located between compound EuDyCuS₃ and solid solutions based on compounds β-Cu₂S, EuS, DyCuS₂, β-(DyCu₃S₃), and EuDy₂S₄; between DyCuS₂ and the solid solution of α-Dy₂S₃, DyCuS₂, and EuDy₂S₄.     

Ternary Systems LiBr–LiVO<Subscript>3</Subscript>–Li<Subscript>2</Subscript>CrO<Subscript>4</Subscript> and KBr–KVO<Subscript>3</Subscript>–K<Subscript>2</Subscript>CrO<Subscript>4</Subscript>

The binary system KVO₃–K₂CrO₄ and two ternary systems, LiBr–LiVO₃–Li₂CrO₄ and KBr–KVO₃–K₂CrO₄, were studied. In the ternary systems, the compositions and melting points of eutectic alloys were determined by differential thermal analysis: (49.0 mol % LiBr, 5.0 mol % LiVO₃, 46.0 mol % Li₂CrO₄, 400°C) and (17.0 mol % KBr, 78.0 mol % KVO₃, 5.0 mol % K₂CrO₄, 458°C), respectively.     

Multicomponent systems LiCl–LiBr–Li<Subscript>2</Subscript>SO<Subscript>4</Subscript> and LiCl–LiBr–Li<Subscript>2</Subscript>SO<Subscript>4</Subscript>–Li<Subscript>2</Subscript>MoO<Subscript>4</Subscript>

Phase equilibria in the LiCl–LiBr–Li₂SO₄ ternary system and the LiCl–LiBr–Li₂SO₄–Li₂MoO₄ quaternary system were studied by differential thermal analysis. The compositions and temperatures of minima in the ternary and quaternary systems were determined to be (31.2 mol % LiCl, 46.8 mol % LiBr, 22.0 mol % Li₂SO₄, 460°C) and (25.2 mol % LiCl, 30.2 mol % LiBr, 14.6 mol % Li₂SO₄, 30.0 mol % Li₂MoO₄, 411°C), respectively.     

Magnetic Phase Diagram of Solid Solutions in the CoCr<Subscript>2</Subscript>S<Subscript>4</Subscript>–Cu<Subscript>0.5</Subscript>Ga<Subscript>0.5</Subscript>Cr<Subscript>2</Subscript>S<Subscript>4</Subscript> System

The magnetic phase diagram of solid solutions in the CoCr₂S₄–Cu_0.5Ga_0.5Cr₂S₄ system was constructed. The widest concentration range (0.38 < x < 1) in the diagram represents solid solutions based on the ferrimagnetic semiconductor CoCr₂S₄ (T_C = 223 K), which exhibits unusual properties in the magnetic ordering region while measuring the temperature dependence of the dynamic susceptibility. The magnetic properties were studied with a Quantum Design PPMS-9 platform within the temperature range 5–300 K in a 100-Oe constant magnetic field and/or a varying (100-, 500-, and 1000-Hz) magnetic field with an amplitude of 1 Oe.     

Interaction in the systems TlBiSe<Subscript>2</Subscript>–Tl<Subscript>9</Subscript>BiSe<Subscript>6</Subscript>–PbSe and Tl<Subscript>9</Subscript>BiSe<Subscript>6</Subscript>–Tl<Subscript>4</Subscript>PbSe<Subscript>3</Subscript>–PbSe

Phase equilibria in the systems TlBiSe₂–Tl₉BiSe₆–PbSe and Tl₉BiSe₆–Tl₄PbSe₃–PbSe were studied by differential thermal, X-ray powder diffraction, and microstructural analyses. State diagrams of the quasi-binary sections Tl₉BiSe₆–Tl₄PbSe₃, TlBiSe₂–PbSe, and Tl₉BiSe₆–PbSe were constructed, and so were projections of liquidus surfaces and isothermal sections at 600 K for the secondary quasi-ternary systems TlBiSe₂–Tl₉BiSe₆–PbSe and Tl₄PbSe₃–Tl₉BiSe₆–PbSe. The coordinates of invariant points and the boundaries of solid solutions were determined.     

Thermal studies of ZnO–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript>–TeO<Subscript>2</Subscript> glasses

The effect of TeO₂ additions on the thermal behaviour of zinc borophosphate glasses were studied in the compositional series (100 − x)[0.5ZnO–0.1B₂O₃–0.4P₂O₅]–xTeO₂ by differential scanning calorimetry, thermodilatometry and heating microscopy thermal analysis. The addition of TeO₂ to the starting borophosphate glass resulted in a linear increase of glass transition temperature and dilatometric softening temperature, whereas the thermal expansion coefficient decreased. Most of glasses crystallize under heating within the temperature range of 440–640 °C. The crystallization temperature steeply decreases with increasing TeO₂ content. The lowest tendency towards crystallization was observed for the glasses containing 50 and 60 mol% TeO₂. X-ray diffraction analysis showed that major compounds formed by annealing of the glasses were Zn₂P₂O₇, BPO₄ and α-TeO₂. Annealing of the powdered 50ZnO–10B₂O₃–40P₂O₅ glass leads at first to the formation of an unknown crystalline phase, which is gradually transformed to Zn₂P₂O₇ and BPO₄ during subsequent heating.     

Electronic and ionic zeebeck coefficients in mixed conductors of Ag<Subscript>0.25–δ</Subscript>Cu<Subscript>1.75</Subscript>Se,Ag<Subscript>1.2–δ</Subscript>Cu<Subscript>0.8</Subscript>Se

The paper presents the studies of ionic and electronic Zeebeck coefficients and electronic conductivity in nonstoichiometric Ag_0.25–δCu_1.75Se, Ag_1.2–δCu_0.8Se solid solutions existing on the basis of the cubic phase of copper selenide. It is shown that Ag_1.2–δCu_0.8Se is a bilateral variable composition phase manifesting inversion of the sign of predominant charge carriers under variation of the chemical composition by silver within the homogeneity region. Mobilities of electrons and electron holes are estimated on the basis of the concentration dependences.     

Phase formation in the system Li<Subscript>2</Subscript>MoO<Subscript>4</Subscript>–MgMoO<Subscript>4</Subscript>–Sc<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript>

Phase formation in the system Li₂MoO₄–MgMoO₄–Sc₂(MoO₄)₃ was studied by X-ray powder diffraction analysis and differential thermal analysis. Ternary molybdate LiMgSc(MoO₄)₃ was synthesized, which crystallizes in the triclinic system (space group P\(\bar 1\)). In the Li₂Mg₂(MoO₄)₃–Li₃Sc(MoO₄)₃ section, a continuous solid solution in the rhombic system was found to form (space group Pnma).     

Thermogravimetric analysis of wheatleyite Na<Subscript>2</Subscript>Cu<Superscript>2+</Superscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>2</Subscript>·2H<Subscript>2</Subscript>O

Evidence for the existence of primitive life forms such as lichens and fungi can be based upon the formation of oxalates. These oxalates form as a film like deposit on rocks and other host matrices. The anhydrous oxalate mineral moolooite CuC₂O₄ as the natural copper(II) oxalate mineral is a classic example. Another example of a natural oxalate is the mineral wheatleyite Na₂Cu²⁺(C₂O₄)₂·2H₂O. High resolution thermogravimetry coupled to evolved gas mass spectrometry shows decomposition of wheatleyite at 255°C. Two higher temperature mass losses are observed at 324 and 349°C. Higher temperature mass losses are observed at 819, 833 and 857°C. These mass losses as confirmed by mass spectrometry are attributed to the decomposition of tennerite CuO. In comparison the thermal decomposition of moolooite takes place at 260°C. Evolved gas mass spectrometry for moolooite shows the gas lost at this temperature is carbon dioxide. No water evolution was observed, thus indicating the moolooite is the anhydrous copper(II) oxalate as compared to the synthetic compound which is the dihydrate.     

Thermal evolution of ceramic powders surrounding the YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7–x</Subscript> composition

Organometallic-derived ceramic compositions surrounding YBa₂Cu₃O_7–x (123) were evaluated via DTA-TG runs and dilatometric densification. The compositions were either Y, Ba or Cu deficient respect to 123. For the Yttrium deficient compact the presence of liquids containing 0–1.3 mole %YO_1.5—capable of dissolving the 123 grains—can promote a rapid sintering behavior. For Copper deficient compact the main densification/contraction mechanisms were delayed till 985 °C. For both Barium and Copper deficient compacts a strong exudation of liquids was detected at 990 °C and 1020 °C, respectively.     

Thermoelectric power and electrochemical studies on CdI<Subscript>2</Subscript>–Ag<Subscript>2</Subscript>O–V<Subscript>2</Subscript>O<Subscript>5</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript> system

A quaternary super-ion-conducting system, 20CdI₂ − 80[xAg₂O − y(0.7V₂O₅ − 0.3B₂O₃)] where 1 ≤ x/y ≤ 3, has been prepared by melt quenching technique. The electrical conductivity measured was the order of 10⁻⁴  S/cm at room temperature. The values of silver-ion transport number obtained by electromotive force technique are nearly unity. The thermoelectric power and electrochemical studies were done on the CdI₂–Ag₂O–V₂O₅–B₂O₃ system. The discharge and polarization characteristics were examined for different cathodes to evaluate the utility of these cells as power sources for low energy applications.     

Glass Formation in the Ternary System La<Subscript>2</Subscript>O<Subscript>3</Subscript>–As<Subscript>2</Subscript>S<Subscript>3</Subscript>–Er<Subscript>2</Subscript>O<Subscript>3</Subscript>

The boundaries of the glass formation region in the ternary system La₂O₃–As₂S₃–Er₂O₃ were found. Transparent glass of composition (La₂O₃)_0.03(As₂S₃)0.90(Er₂O₃)0.07 was studied by X-ray photoelectron and Raman spectroscopy. The intensities of the bands characterizing As–S, La–O, and Er–O bonds increased, and these bands were shifted toward higher energies. This was due to an increase in the covalence of these bonds and probably due to the formation of new bonds in the glasses. Samples in the glass formation region are resistant at 300 K to air, water, and organic solvents.     

Physicochemical Analysis of the System Zr(SO<Subscript>4</Subscript>)<Subscript>2</Subscript>–Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>–H<Subscript>2</Subscript>SO<Subscript>4</Subscript>–H<Subscript>2</Subscript>O at 25°С

The solubility in the quaternary water–salt system Zr(SO₄)₂ · 4Н₂О–Na₂SO₄–H₂SO₄–H₂O at 25°C was studied. It was found that, in the system, there is crystallization of not only Na₂SO₄ and Zr(SO₄)₄ · 4H₂O, but also sodium sulfate zirconates Na₂Zr(SO₄)₂(OH)₂ · 0.3H₂O, Na₄Zr(SO₄)₄ · 3H₂O, and Na₂Zr(SO₄)₂ · 3H₂O and two new compounds, S₁ and S₂, which are presumably Na₂ZrO(SO₄)₂ · 2H₂O and Na₂Zr₂O₂(SO₄)₃ · 6H₂O.     

Phase equilibria in the Cu–Cu<Subscript>2</Subscript>Se–As system

Phase equilibria in the Cu–Cu₂Se–As were investigated by differential thermal analysis and X-ray powder diffraction analysis. Informative plots describing this system were constructed, viz., the polythermal sections Cu_0.667Se_0.333–As, Cu_0.667Se_0.333–Cu_0.735As_0.265, and Cu_0.8Se_0.2–As, the isothermal section of the phase diagram at 300 K, and the projection of the liquidus surface. The obtained results differ from the published data in length of fields of primary crystallization of phases and in coordinates of a number of invariant equilibrium points.     

Glass Formation in the Al<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>3</Subscript>–(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>SO–H<Subscript>2</Subscript>O System

The glass formation in the Al₂(SO₄)₃–(CH₃)₂SO–H₂O system was found for the first time. The competitive ability of ligands, dimethyl sulfoxide and water (which are strong donors), for entering the first coordination sphere of aluminum is considered. The possibility of mixed coordination of (CH₃)₂SO (via sulfur and oxygen atoms) in the first coordination sphere of aluminum with retention of the glass-forming ability of the sample was suggested on the basis of IR spectral study.     

The Sections GeSnSb<Subscript>4</Subscript>Te<Subscript>8</Subscript>–GeTe and GeSnSb<Subscript>4</Subscript>Te<Subscript>8</Subscript>–SnTe of the Quasi-Ternary System GeTe–Sb<Subscript>2</Subscript>Te<Subscript>3</Subscript>–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.     

Distribution of niobium and lanthanum between two immiscible melts in the system LaPO<Subscript>4</Subscript>–SiO<Subscript>2</Subscript>–NaF–Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>

The system LaPO₄–SiO₂–NaF–Nb₂O₅–Fe₂O₃ is characterized by immiscibility fields in the liquid state region. Addition of iron expands fields of immiscibility of melts and decreases the temperature of their coexistence. A fraction of 87–90% of niobium is extracted into iron silicate melt, and 92–98% of lanthanum is extracted into phosphate salt melt.     

Phase Diagram of the System Tl<Subscript>2</Subscript>Te–Tl<Subscript>5</Subscript>Te<Subscript>3</Subscript>–Tl<Subscript>9</Subscript>GdTe<Subscript>6</Subscript>

The ternary system Tl–Gd–Te within the composition range Tl₂Te–T_l5Te₃–T_l9GdTe₆ 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.