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.     

Stable triangle (LiF)<Subscript>2</Subscript>–(KI)<Subscript>2</Subscript>–Li<Subscript>2</Subscript>CrO<Subscript>4</Subscript> of the quaternary reciprocal system Li,K∥F,I,CrO<Subscript>4</Subscript>

The quaternary reciprocal system Li,K||F,I,CrO₄ was partitioned into stable simplexes using graph theory. The system consists of five stable tetrahedra separated by four stable triangles. The chemical interaction between components was described based on the material balance written with account for occurring chemical reactions. Phase equilibria in the quasi-ternary system (LiF)₂–(KI)₂–Li₂CrO₄ were studied for the first time; in this system, the temperature and composition of a ternary eutectic were determined. The limited solubility of two liquid phases manifests itself in the concentration region adjacent to the LiF–KI quasibinary system. A three-dimensional model of the phase complex of the system was constructed in temperature– concentration coordinates.     

Phase equilibria in the NaCl–KI–K<Subscript>2</Subscript>CrO<Subscript>4</Subscript> stable triangle of the Na,K‖Cl,I,CrO<Subscript>4</Subscript> system

The NaCl–KI–K₂CrO₄ stable triangle was studied by differential thermal analysis. The melting temperature, melt composition, and specific melting enthalpy corresponding to the ternary eutectic were determined in the system. The compositions of crystallizing phases in the eutectic were confirmed by X-ray diffraction.     

Phase equilibria in the stable tetrahedron LiF–LiBr–Li<Subscript>2</Subscript>CrO<Subscript>4</Subscript>–KBr of the quaternary reciprocal system Li,KǁF,Br,CrO<Subscript>4</Subscript>

Phase equilibria in the stable tetrahedron LiF–LiBr–Li₂CrO₄–KBr of the quaternary reciprocal system Li,K∥F,Br,CrO₄ were studied by differential thermal analysis. The composition (equiv %) and melting point of a quaternary eutectic were found as (2% LiF, 60% LiBr, 3% Li₂CrO₄, 35% KBr, 315°C).     

Phase Equilibria in the System LiF–KI–KF–K<Subscript>2</Subscript>CrO<Subscript>4</Subscript>

Phase equilibria were experimentally studied in the system LiF–KI–KF–K₂CrO₄, which is the stable tetrahedron of the quaternary reciprocal system Li, K∥F, I, CrO₄. Differential thermal analysis revealed the compositions and transformation temperatures at the eutectic point E^□ 488 (L ? LiF + KF + KI + α-K₂CrO₄) and the peritectic point P^□ 510 (L + K₃FCrO₄ ? KI + α-K₂CrO₄ + KF). A computer model of the phase complex of the system was built, which can predict phase transformations at an arbitrary composition in the system. Isothermal sections of the systems were constructed, using which the phase composition at the temperature of the section can be calculated.     

Ternary Systems NaHal–NaVO<Subscript>3</Subscript>–Na<Subscript>2</Subscript>CrO<Subscript>4</Subscript> (Hal = Cl,Br)

Phase equilibria in the ternary systems NaHal–NaVO₃–Na₂CrO₄ (Hal = Cl, Br) were studied. By differential thermal analysis, eutectic alloys were found at points with coordinates (14.0 mol % NaCl, 66.5 mol % NaVO3, 19.5 mol % Na₂CrO₄, 530°C) and (27.0 mol % NaBr, 47.5 mol % NaVO₃, 25.5 mol % Na₂CrO₄, 499°C). By differential scanning calorimetry, the specific enthalpies of melting of the eutectics were determined. X-ray powder diffraction analysis of the eutectic alloy in the system NaBr–NaVO₃–Na₂CrO₄ was made.     

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.     

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).     

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.     

Theoretical analysis of the system Li,K, Ca,Ba||F,WO<Subscript>4</Subscript>: Physicochemical properties of the system LiF–K<Subscript>2</Subscript>WO<Subscript>4</Subscript>–BaF<Subscript>2</Subscript>–CaF<Subscript>2</Subscript>–BaWO<Subscript>4</Subscript>

The differentiation of the quaternary reciprocal system Li, K, Ca, Ba||F, WO₄ was performed based on the graph theory using special software. Stable and metastable complexes of the system were found using a matrix of reciprocal pairs of salts. For the first time, by a set of physicochemical analysis methods (differential thermal, visual polythermal, and X-ray powder diffraction analyses), based on the method of thermal analysis of successive projections of the composition polytope, the quaternary system LiF–K₂WO₄–CaF₂–BaF₂–BaWO₄, which is a stable complex of the quaternary reciprocal system Li, K, Ca, Ba||F, WO₄, was studied and the coordinates of invariant points were determined.     

System RbF–RbBr–Rb<Subscript>2</Subscript>SO<Subscript>4</Subscript>

The three-component system RbF–RbBr–Rb₂SO₄ has been studied by differential thermal analysis (DTA). The melting temperatures and compositions corresponding to a eutectic point and a peritectic point have been determined. Invariant, monovariant, and divariant equilibrium states are described.     

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.     

Synthesis and crystal structure of [UO<Subscript>2</Subscript>CrO<Subscript>4</Subscript>(C<Subscript>5</Subscript>NH<Subscript>5</Subscript>COO)] · H<Subscript>2</Subscript>O

Synthesis and X-ray diffraction study of [UO₂CrO₄(C₅NH₅COO)] · H₂O crystals were performed. The compound crystallizes in the monoclinic system with the unit cell parameters a = 7.5025(3) Å, b = 11.5188(6) Å, c = 13.0518(6) Å, β = 97.877(4)°, V = 1117.29(9) ų, space group P2₁/n, Z = 4, R = 0.0263. The structure is formed by three [UO₂CrO₄(C₅NH₅COO)] layers parallel to (10\(\bar 1\)). The coordination polyhedron of uranium atoms is a pentagonal bipyramid, whose apices are occupied by oxygen atoms of uranyl, three chromate groups, and two molecules of isonicotinic acid. Crystal chemical formula of the [UO₂CrO₄(C₅NH₅COO)] layer can be represented as AT³B², where A = UO ₂ ²⁺ , T³ = CrO ₄ ^2? , and B² = C₅NH₅COO molecules. The isonicotinic acid molecules are in the form of zwitterions.     

Crystal structure of Na<Subscript>3</Subscript>(NH<Subscript>4</Subscript>)<Subscript>2</Subscript>[Ir(SO<Subscript>3</Subscript>)<Subscript>2</Subscript>Cl<Subscript>4</Subscript>]·4H<Subscript>2</Subscript>O

The complex Na₃(NH₄)₂[Ir(SO₃)₂Cl₄]·4H₂O was examined with single crystal X-ray diffraction and IR spectroscopy. Crystal data: a = 7.3144(4) Å, b = 10.0698(5) Å, c = 12.3748(6) Å, β = 106.203(1)°, V = 875.26(8) ų, space group P2₁/c, Z = 2, d _calc = 2.547 g/cm³. In the complex anion two trans SO ₃ ^2? groups are coordinated to iridium through the S atom. The splitting of O-H bending vibrations of crystallization water molecules and N-H ones of the ammonium cation is considered in the context of different types of interactions with the closest neighbors in the structure.     

Phase Equilibria in the System Tl<Subscript>9</Subscript>SbSe<Subscript>6</Subscript>–TlSbSe<Subscript>2</Subscript>–Tl<Subscript>4</Subscript>SnSe<Subscript>4</Subscript>

For the first time, by differential thermal, X-ray powder diffraction, and microstructural analyses, phase equilibria in the ternary system Tl₉SbSe₆–TlSbSe₂–Tl₄SnSe₄ were investigated and the state diagram of the polythermal section Tl₄SnSe₄–Tl₃SbSe₃, the projection of the liquidus surface on the concentration triangle, and the isothermal section at 423 K were constructed. The types and coordinates of invariant processes, the lines of monovariant equilibria, and their temperature ranges were found. The formation mechanism and nature of solid solutions based on ternary compounds Tl₉SbSe₆ and TlSbSe₂ were studied in terms of crystal chemistry.     

Study of the stable tetrahedron LiVO<Subscript>3</Subscript>–Li<Subscript>2</Subscript>MoO<Subscript>4</Subscript>–KBr–LiKMoO<Subscript>4</Subscript> of the quaternary reciprocal system Li,KǁBr,VO<Subscript>3</Subscript>,MoO<Subscript>4</Subscript>

Phase equilibria in the stable tetrahedron LiVO₃–Li₂MoO₄–KBr–LiKMoO₄ of the quaternary reciprocal system Li,K∥Br,VO₃,MoO₄ were studied by differential thermal analysis. The composition (mol %) and melting point of the alloy corresponding to a quaternary eutectic were determined: (24.2% LiVO₃, 10.4% Li₂MoO₄, 13.5% KBr, 51.9% LiKMoO₄, 407°С).     

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.     

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.     

High-temperature heat capacity of Pb<Subscript>8</Subscript>La<Subscript>2</Subscript>(GeO<Subscript>4</Subscript>)<Subscript>4</Subscript>(VO<Subscript>4</Subscript>)<Subscript>2</Subscript> in the range 320–1000 K

The oxide compound Pb₈La₂(GeO₄)₄(VO₄)₂ with an apatite structure has been synthesized by a ceramic method. The effect of temperature on the molar hear capacity of polycrystalline samples in the temperature range 320–1000 K has been studied by differential scanning calorimetry. The results have been used to calculate the thermodynamic functions of the synthesized compound.     

Tree of phases of the quinary reciprocal system Li,K || F,Br, MoO<Subscript>4</Subscript>, WO<Subscript>4</Subscript> and study of the stable tetrahedron LiF–KBr–Li<Subscript>2</Subscript>MoO<Subscript>4</Subscript>–Li<Subscript>2</Subscript>WO<Subscript>4</Subscript>

The quinary reciprocal system Li, K || F, Br, MoO₄, WO₄ was partitioned into simplexes using graph theory by writing an adjacency matrix and solving a logical expression. A tree of phases of the system was constructed. The tree of phases has a linear structure and consists of four stable partitioning tetrahedra, two stable pentatopes, and three stable hexatopes. In the quinary reciprocal system Li, K || F, Br, MoO₄, WO₄, crystallizing phases were predicted. The stable tetrahedron LiF–KBr–Li₂MoO₄–Li₂WO₄ of the quinary reciprocal system Li, K || F, Br, MoO₄, WO₄ was studied by differential thermal analysis and X-ray powder diffraction. There are no invariant equilibrium points in the tetrahedron. Continuous series of solid solutions Li₂Mo_xW_1–xO₄ do not decompose.