Four-component system LiF-K2WO4-CaF2-CaWO4

The four-component system LiF-K₂WO₄-CaF₂-CaWO₄ has been studied by physicochemical analysis. The phase and crystallization trees have been predicted a priori and have been experimentally verified by constructing a topological model of the phase diagram and by solving the equations expressing the general law of liquidus surface formation. The heat-storage properties of the eutectic compositions are evaluated.     

Phase complex of the quaternary system LiF-SrFCl-SrCO3-SrMoO4 and the thermodynamic properties of its eutectics

By physicochemical analysis methods, the quaternary system LiF-SrFCl-SrCO₃-SrMoO₄ was studied for the first time. The tree of phases and the tree of crystallization of the system were constructed by an a priori prediction method. The compositions and temperatures at invariant points were determined, and the phase diagram of the system was constructed, the liquidus surface of which is represented by the crystallization fields of the initial compounds and the incongruently melting binary compounds Sr₅F₄Cl₄CO₃, Sr₂FClCO₃, and LiSrFCO₃. The heat-storage properties of eutectics in the system were evaluated.     

Four-component system LiF-K<Subscript>2</Subscript>WO<Subscript>4</Subscript>-CaF<Subscript>2</Subscript>-BaWO<Subscript>4</Subscript>

The four-component system LiF-K₂WO₄-CaF₂-BaWO₄ has been studied for the first time using physicochemical methods. The a priori prediction of the phase complex revealed the phase tree and crystallization path of the system. The prediction was verified experimentally, by construction of a topologic model of the phase diagram, and the solution of the equations of the general law of liquidus-surface formation. The density has been measured, and the heat-storage properties of eutectic mixtures have been estimated.     

Tree of phases of the Li,Na,Ba‖F,Br quaternary reciprocal system and study of the LiF-NaBr-BaFBr stable triangle

The Li,Ba‖F,Br ternary reciprocal system was investigated by differential thermal analysis. The T-x diagrams of the polythermal sections studied and the liquidus of the system were constructed. It was deter-mined that the system is of the adiagonal section type with a subordinate diagonal (according to Bergman’s classification). The characteristics and enthalpies of melting of the alloys corresponding to invariant equilibrium points were found. The Li,Na,Ba‖F,Br quaternary reciprocal system was partitioned, and the tree of phases was constructed. The LiF-NaBr-D₁(BaFBr) stable triangle was experimentally studied, the liquidus was constructed, and the characteristics of the alloy corresponding to a ternary eutectic were determined.     

Interaction of components in the Tl<Subscript>2</Subscript>Se-Tl<Subscript>4</Subscript>SnSe<Subscript>4</Subscript>-Tl<Subscript>9</Subscript>SbSe<Subscript>6</Subscript> quasi-ternary system

The interaction in the Tl₂Se-Tl₄SnSe₄-Tl₉SbSe₆ quasi-ternary system was studied by differential thermal analysis, X-ray powder diffraction analysis, and mathematical modeling. The projection of the liquidus surface and a spatial phase diagram of the system were constructed. It was determined that this system is of the eutectic type with boundary solid solutions based on the initial components. No formation of new intermediate compounds in the quasi-ternary system was detected.     

System NaOH-Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>-Na<Subscript>2</Subscript>S

The NaOH-Na₂SO₄-Na₂S system has been studied. Refined phase diagrams have been designed for the boundary binaries and for four radiating sections, as well as the liquidus surface for the ternary system.     

Phase equilibria in the NaCl-NaBr-Na<Subscript>2</Subscript>MoO<Subscript>4</Subscript> system

The binary systems NaBr-Na₂MoO₄ and NaBr-Na₃ClMoO₄ and the ternary system NaCl-NaBr-Na₂MoO₄ have been studied using physicochemical methods (DTA and powder X-ray diffraction). The compositions, melting points, and heats of phase transitions have been determined for three invariant points. The liquidus surface of the ternary system consists of the fields of sodium molybdate, Na₃ClMoO₄, and sodium chloride and bromide solid solutions. The eutectics melt at 531, 612, and 524°C; the respective heats of phase transitions are 149.27, 167.55, and 215.38 J/g.     

Phase equilibria in the Tl2Te-PbTe-Bi2Te3 system

Phase equilibria in the Tl₂Te-PbTe-Bi₂Te₃ system were studied by differential thermal analysis, X-ray powder diffraction, and microhardness measurements. Some polythermal sections and isothermal (at 600 and 800 K) sections of the phase diagram and a projection of the liquidus surface were constructed. It was shown that the system is characterized by the formation of solid solutions with the Tl₅Te₃ structure (??) and solid solutions based on PbTe (??₁), Tl₂Te (??), Bi₂Te₃ (??), and two TlBiTe₂ (??₂ and ?á?₂) phases. Their homogeneity regions were determined. The liquidus surface consists of the primary crystallization fields of the ??-, ??₁-, ?á?₂-, and ??-phases and the compounds PbBi₂Te₄ and PbBi₄Te₇. The liquidus of the ?? phase is degenerate. The primary crystallization fields of the phases were determined, and the types and coordinates of in- and monovariant equilibria were found.     

Phase equilibria in the Tl2Te-SnTe-Bi2Te3 system

phase equilibria in the Tl₂Te-SnTe-Bi₂Te₃ system were studied by differential thermal analysis (DTA), X-ray powder diffraction, and microhardness measurements. Some polythermal sections and isothermal (at 600 and 800 K) sections of the phase diagram and a projection of the liquidus surface were constructed. It was shown that the system is characterized by the formation of solid solutions with the Tl₅Te₃ structure (δ) and solid solutions based on SnTe (γ₁), Tl₂Te (α), Bi₂Te₃ (β), and two TlBiTe₂ (γ₂ and γ′₂) phases. Their homogeneity regions were determined. The liquidus surface consists of the primary crystallization fields of the β-, γ₁-, γ′₂-, and δ phases and the compounds SnBi₂Te₄ and SnBi₄Te₇. The liquidus of the α phase is degenerate. The primary crystallization fields of phases were determined, and the types and coordinates of in- and monovariant equilibria were found.     

Thermodynamic Properties of silicate glasses and melts: VIII. System MgO-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript>

Vaporization of the system MgO-Al₂O₃-SiO₂ in the temperature range 1770–1890 K was studied and activities of MgO and SiO₂ were determined. Activities of the components, isothermal sections of the phase diagram, and the position of the liquidus line in the studied system were calculated using the Gay-Kapoor-Frohberg model. The correlation of the found values of thermodynamic properties and phase equilibriua in isothermal sections of the phase diagram of the studied system was illustrated.     

Partitioning of the quinary reciprocal system Li,K‖F,Cl,Br,MoO4 into simplexes and the investigation of its partitioning and stable elements

The quinary reciprocal system Li,K‖F,Cl,Br,MoO₄ was partitioned into simplexes using graph theory. A tree of phases of the system was constructed, and stable elements were identified. The chemical interaction in the system Li,K‖F,Cl,Br,MoO₄ was described by the ion balance method. The stable tetrahedra LiF-KCl-KBr-K₂MoO₄, LiF-KCl-KBr-LiKMoO₄, and LiF-Li₂MoO₄-KCl-KBr and the united stable pentatope LiF-KF-KCl-KBr-K₂MoO₄ were studied by differential thermal analysis, and phase states in the studied simplexes were determined. The compositions of crystallizing phases in the bulk of the studied tetrahedra and pentatope were confirmed by X-ray powder diffraction analysis.     

Partitioning of the quaternary reciprocal system Li,K‖Cl,Br,MoO4 into simplexes and investigation of its partitioning and stable elements

The quaternary reciprocal system Li,K‖Cl,Br,MoO₄ was partitioned into simplexes using graph theory. A tree of phases of the system was constructed, and stable elements were identified. The stable triangles LiKMoO₄-KCl-KBr and Li₂MoO₄-KCl-KBr and the stable tetrahedron Li₂MoO₄-K₂MoO₄-KCl-KBr were studied by differential thermal analysis, and phase states in the triangles and the tetrahedron were determined.     

Phase diagram for the ternary system LiClCaCl2CaCrO4

The phase diagram for the system LiClCaCl₂CaCrO₄ has been studied using differential thermal analysis. LiClCaCl₂CaCrO₄ has been shown by X-ray diffraction to be a stable, diagonal section of the Li, Ca//Cl, CrO₄ reciprocal ternary system. The three binary systems are: LiClCaCl₂ which exhibits a double salt (LiCaCl₃), which decomposes without melting at 439°C and a eutectic at 36.3 mole % CaCl₂ (m.p. 487°C); CaCl₂CaCrO₄ which shows a eutectic at 23.4 mole % CaCrO₄ (m.p. 660°C); and LiClCaCrO₄ with a eutectic at 14.3 mole % CaCrO₄ (m.p. 538°C).In the ternary system, a eutectic exists at 63.2 mole % LiCl32.9% CaCl₂3.9% CaCrO₄ (m.p. 479°C). In addition, a four-phase equilibrium, involving all solid phases, exists at nearly all compositions at 435°C.Isotherms are shown for the liquidus surface (primary crystallization) and for the secondary crystallization surface. Isothermal and vertical sections through the ternary phase diagram are shown.     

Primary crystallization region of the chalcopyrite phase in the CuInSe2-Sn-Se system

Interactions in the CuInSe₂-Sn-Se quasi-ternary system were studied by DTA, X-ray powder diffraction, microstructural analysis and microhardness measurements. A projection of the liquidus surface of the phase diagram was constructed, where the boundaries of the primary crystallization region of the low-temperature chalcopyrite phase were determined. The existence of the compound CuInSnSe₂ was established, which forms at 610°C by a peritectic reaction.     

Phase equilibria in the Cu<Subscript>2</Subscript>S–Cu<Subscript>3</Subscript>AsS<Subscript>4</Subscript>–S system

Phase equilibria in the Cu₂S–Cu₃AsS₄–S system were studied by differential thermal analysis and X-ray powder diffraction. Important plots characterizing this system were constructed, namely, the T–x diagrams of the lateral quasi-binary systems Cu₂S–Cu₃AsS₄ and Cu₃AsS₄–S, some internal sections, the isothermal section of the phase diagram at 300 K, and the projection of the liquidus surface. The fields of primary crystallization of phases and the types and coordinates of in- and monovariant equilibria were found. A wide region of separation of liquid phases was detected in the system.     

Physicochemical interaction in the TlSe-Tl2SnSe3-Se quasi-ternary system

The physicochemical interaction in the TlSe-Tl₂SnSe₃-Se quasi-ternary system was studied by differential thermal analysis, X-ray powder diffraction, and mathematical modeling. A projection of the liquidus surface and the three-dimensional phase diagram of the TlSe-Tl₂SnSe₃-Se quasi-ternary system were constructed. It was determined that this system is of the eutectic type and limited solid solutions based on the initial components form in it. New intermediate compounds were not observed in the quasi-ternary system.     

(Solid+Liquid) Equilibria in the Quaternary System Na2B4O7-MgB4O7-K2B4O7-H2O at 288 K

(Solid+Liquid) phase equilibria in the quaternary system Na₂B₄O₇‐MgB₄O₇‐K₂B₄O₇‐H₂O at 288 K were studied experimentally using the method of isothermal solution saturation. Solubility of any single salt in the solution of the quaternary system was determined experimentally. Based on the experimental data achieved, the phase diagram and water content diagram of the quaternary system were constructed, respectively. In the phase equilibrium diagram of the quaternary system Na₂B₄O₇‐MgB₄O₇‐K₂B₄O₇‐H₂O at 288 K, there are one invariant point E, three univariant curves E1E, E2E and E3E, and three fields of crystallization corresponding to Na₂B₄O₇·10H₂O, K₂B₄O₇·4H₂O and MgB₄O₇·9H₂O. The experimental results show that potassium borate (K₂B₄O₇·4H₂O) have higher solubilities than the magnesium borate and sodium borate in the quaternary system Na₂B₄O₇‐MgB₄O₇‐K₂B₄O₇‐H₂O at 288 K.     

Phase diagram of the eutectic benzoic acid-naphthalene system in the temperature range of 300–400 K

Liquid-solid phase equilibria are studied in the eutectic benzoic acid-naphthalene system by means of thermic analysis (DTA, CTA), on the basis of which the liquidus line and eutectic point (x _e ≈ 50 mol %, T _e ± 340 K) are determined and the phase diagram is constructed. Average precrystallization supercooling temperatures ΔT _L ^? of the liquid phase relative to liquidus temperature T _L are determined, allowing us to locate the region of solution metastability on the phase diagram. Excessive functions of the components in the liquid phase are found via thermodynamic modeling using the Margules equation and experimental data. The boundaries of the region of liquid solution metastability are estimated from the thermodynamic conditions of solution stability.     

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.     

The CaF2-CaCl2-CaSO4 system

The liquidus surface of the CaF₂-CaCl₂-CaSO₄ system has been investigated by differential thermal analysis. Two invariant equilibria (one eutectic and one peritectic) are realized in the system. The eutectic and peritectic melt at 597 and 703°C, and the enthalpies of phase transitions are 206 and 378.1 kJ/kg, respectively. Investigation of the ternary system formed by the natural minerals fluorite (CaF₂), anhydrite (CaSO₄), and calcium chloride (a relatively low-melting inorganic solvent) is undertaken with the goal of developing power-intensive heat-accumulating phase-transition materials and electrolytes of diversified application. Original Russian Text ? P.A. Arbukhanova, Ya.A. Dibirov, N.N. Verdiev, A.M. Amadziev, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 6, pp. 1043–1045.