Calculation of phase diagrams for the binary systems BaF2-KF and KF-ZrF4 and the ternary system BaF2-KF-ZrF4

This paper presents the thermodynamic modeling of excess functions and the phase diagram calculation of the ternary system BaF₂-KF-ZrF₄ based on the Hoch-Arpshofen model. The information required was the thermodynamic quantities relative to the three pure salts and the three limiting binary mixtures. The calculated position of the “deep” ternary eutectic allows the prediction of the composition glass range.     

Phase diagrams of sections in the EuS-Cu2S-Nd2S3 system

Phase equilibria in the EuS-Cu₂S-Nd₂S₃ system were studied in an isothermal (970 K) section and NdCuS₂-EuS and Cu₂S-EuNdCuS₃ polythermal sections. The complex sulfide EuNdCuS₃ has an orthorhombic crystal lattice (space group Pnma; a = 1.10438(2) nm, b = 0.40660(1) nm, c = 1.14149(4) nm), is isostructural to BaLaCuS₃, and melts incongruently at 1470 K: EuNdCuS₃ (0.50 EuS; 0.50 NdCuS₂) ai 0.18 EuS ss (0.88 EuS; 0.12 NdCuS₂) + 0.82 L (0.415 EuS; 0.585 NdCuS₂); ΔH = 17.8 kJ/mol. Within the range 0.5 mol % EuS, EuNdCuS₃-based solid solutions were not found. At 970 K, the tie lines pass from the compound EuNdCuS₃ to Cu₂S, EuS, NdCuS₂, and EuNd₂S₄ phases and lie between the NdCuS₂ phase and solid solutions (ss) of γ-Nd₂S₃ with EuNd₂S₄. Eutectics are formed between the compounds NdCuS₂ and EuNdCuS₃ at 32.0 mol % EuS T = 1318 K and between the compounds Cu₂S and EuNdCuS₃ at 20.5 mol % EuNdCuS₃ and T = 1142 K. Five main subordinate triangles were identified in the system.     

LiCl、CaCl_2和NaCl-CaCl_2水溶液体系低温相变过程的X射线衍射法研究

本文使用低温X射线衍射法对不同浓度的LiCl、CaCl2和NaCl-CaCl2水溶液在降温过程中的相变情况进行了实时监测,获得了降温过程中的衍射图。结果显示,在快速降温的实验条件下,随温度降低,CaCl2溶液在-10～-60℃范围内析出冰或CaCl2·6H2O;LiCl溶液在5～-80℃范围内析出冰或LiCl·H2O;CaCl2-NaCl溶液在5～-40℃范围内析出CaCl2·6H2O或NaCl、冰。实验结果与相图的对比验证了这一实验方法的可行性。根据实验结果推断,本实验条件下固相可能先以无水盐的形式析出,而水合盐的形成则需要更长的平衡时间。本文的实验方法可为其他油田卤水子体系低温相平衡的研究提供有用信息,进而为油田水低温下结晶析盐规律的研究奠定基础。     

Phase equilibria in the system Na,K,Mg,Ca∥SO4,Cl-H2O at 25°C in the crystallization regions of MgCl2·6H2O, CaCl2·6H2O, and 2MgCl2·CaCl2·12H2O

The translation method is used to study equilibria in the system Na, K, Mg, Ca∥SO₄, Cl-H₂O at 25°C in the crystallization regions of MgCl₂·6H₂O, CaCl₂·6H₂O, and 2MgCl₂·CaCl₂·12H₂O. The participation of these salts in the formation of the geometrical images of the title system is determined. The relevant fragments of the equilibrium phase diagram are designed. Original Russian Text ? L. Soliev, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 5, pp. 841–845.     

The Li2CrO4---CaCrO4 binary phase diagram

Phase equilibria in the Li₂CrO₄---CaCrO₄ system were determined by differential thermal analysis and X-ray powder diffraction. The phase diagram is characterized by a eutectic reaction at 489°C and 5 mole% CaCrO₄, and a monotectic reaction at 570°C and 80 mole% CaCrO₄. The solubility of Li₂CrO₄ in CaCrO₄ was ≈15 mole% at the eutectic temperature and declined to <5 mole% at the monotectic temperature. No double salt was formed between the end members. The immiscibility observed in the system is rationalized in terms of the cation coordination polyhedra.

Thermal events indicative of a solid state phase change in Li₂CrO₄ as reported in some references are judged to be the result of a Li₂CO₃ impurity.     

T-x1-x2 model phase diagrams with upper and lower critical stratification temperatures in the starting binary systems

T-x ₁-x ₂ model phase diagrams have been developed under the condition that the component binary systems had closed regions with upper and lower critical stratification temperatures, as well as monotectic equilibria. Isothermal sections in different interinvariant intervals are given.     

Cobalt tungstate synthesis in melts of the (K2WO4-KCl)eut-CoSO4 (K,Co‖Cl,SO4,WO4) system

A rational process is developed for preparing cobalt tungstate. Cobalt tungstate samples are synthesized and identified in melts of the(K₂WO₄-KCl)_eut-CoSO₄ (K,Co‖Cl,SO₄,WO₄) system.     

Phase equilibria in systems based on Tl4SnSe3 and Tl4SnSe4 ternary compounds

Phase equilibria in the Tl₄SnSe₃-Tl (I), Tl₄SnSe₃-Sn (II), Tl₄SnSe₄-SnSe (III), Tl₄SnSe{ia4}-TlSe (IV), and Tl₄SnSe₃-Tl₄SnSe₄ (V) systems have been studied by differential thermal analysis and power X-ray diffraction. Systems I–V have been found to have eutectic interactions. In systems I and II, width regions of solid solutions based on the ternary compound Tl₄SnSe₃ are formed.     

Phase formation in the Dy2O3-HfO2-MoO3 system. Crystal structure of the new binary molybdate Dy2Hf2(MoO4)7

Phase relations have been studied for the subsolidus region of the Dy₂O₃-HfO₂-MoO₃ system; binary molybdates, Dy₂Hf(MoO₄)₅ and Dy₂Hf₂(MoO₄)₇, were found to form. The crystal structure of the latter has been solved (a = 20.661(3) , b = 9.816(1) , c = 13.796(3) , = 113.47(1)°, Z = 4, space group C2/c, R = 0.023) and found to be a new type of structure. In the structure, MoO₄ tetrahedra are linked by their vertices with HfO₆ octahedra and DyO₈ tetragonal antiprisms to form a 3D open-work, in which one can isolate double-row tetrahedral and octahedral chains extended down the c axis.Original Russian Text Copyright © 2004 by S. F. Solodovnikov, B. G. Bazarov, E. Yu. Badmaeva, Yu. L. Tushinova, E. S. Zolotova, and Zh. G. BazarovaTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 692–697, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

LiCl-LiBr-LiVO3 and LiCl-LiBr-Li2MoO4 ternary systems

Phase equilibria in the LiCl-LiBr-LiVO₃ and LiCl-LiBr-Li₂MoO₄ ternary systems have been investigated by differential thermal analysis. The following compositions have been revealed (mol %): eutectic in the LiCl-LiBr-LiVO₃ system (18.0% LiCl, 72.0% LiBr, and 10.0% LiVO₃) with a melting point of 464°C and specific enthalpy of melting of 213 kJ/kg, and a minimum in the LiCl-LiBr-Li₂MoO₄ system (27.0% LiCl, 48.0% LiBr, and 25.0% Li₂MoO₄) with a melting point of 444°C. The investigation of ternary systems including salts of alkali metals is of practical interest for chemical industry and metallurgy, where salt mixtures are used as fused electrolytes and heat carriers. Original Russian Text ? T.V. Gubanova, E.I. Frolova, I.K. Garkushin, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 7, pp. 1220–1223.     

Ba3 (VO4)2-K2 Ba(MoO4)2 and Pb3 (VO4)2-K2 Pb(MoO4)2 systems

Phase equilibria in the Ba₃(VO₄)₂-K₂Ba(MoO₄)₂ and Pb3(VO₄)₂-K₂Pb(MoO₄)₂ systems have been investigated. In the first system, a continuous series of substitutional solid solutions with the palmierite structure is formed, and in the second one, the polymorphic transition in lead orthovanadate at 100°C restricts the extent of the palmierite-type solid solution to 10–100 mol % K₂Pb(MoO₄)₂. Original Russian Text ? V.D. Zhuravlev, Yu.A. Velikodnyi, A.S. Vinogradova-Zhabrova, A.P. Tyutyunnik, V.G. Zubkov, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 10, pp. 1746–1748.     

Investigation of phase equilibria in the systems K2SO4Sc2(SO4)3, Rb2SO4Sc2(SO4)3 and Cs2SO4Sc2(SO4)3

Phase diagrams of the systems K₂SO₄Sc₂(SO₄)₃, Rb₂SO ₄Sc₂(SO₄)₃ and Cs₂SO₄ Sc₂(SO₄)₃ have been investigated by X-ray diffraction phase analysis and differential thermal analysis techniques. A salient feature of all the systems is the formation of M₃Sc(SO₄)₃, which melt incongruently, and MSc(SO₄)₂, which on heating decompose in the solid state.     

Phase equilibrium relations in the binary systems LiPO3CeP3O9 and NaPO3CeP3O9

The LiPO₃CeP₃O₉ and NaPO₃CeP₃O₉ systems have been investigated for the first time by DTA, X-ray diffraction, and infrared spectroscopy. Each system forms a single 1:1 compound. LiCe(PO₃)₄ melts in a peritectic reaction at 980°C. NaCe(PO₃)₄ melts incongruently, too, at 865°C. These compounds have a monoclinic unit cell with the parameters: a = 16.415(6), b = 7,042(6), c = 9.772(7)Å; β = 126.03(5)°; Z = 4; space group $\text{C}{}_2\text{c}$ for LiCe (PO₃)₄; and a = 9.981(4), b = 13.129(6), c = 7.226(5) Å, β = 89.93(4)°, Z = 4, space group $\text{P2}{}_1\text{n}$ for NaCe(PO₃)₄. It is established that both compounds are mixed polyphosphates with chain structure of the type |M^I_IM^III_II (PO₃)₄|_∞M^I_I: alkali metal, M^III_II: rare earth.     

Phase equilibrium in the PbSnS2-PbSb2S4 system

The PbSnS₂-PbSb₂S₄ system was studied by physicochemical methods, and its phase diagram was plotted. The system is quasi-binary; solid solutions regions based on PbSnS₂ (6 mol % PbSb₂S₄) and PbSb₂S₄ (12 mol % PbSnS₂) were revealed. At a component ratio of 1: 1, a congruently melting compound Pb₂SnSb₂S₆ is formed. Pb₂SnSb₂S₆ single crystals were obtained by chemical transport. The unit cell parameters of Pb₂SnSb₂S₆, which crystallizes in orthorhombic system, were determined: a = 15.22 ?, b = 10.68 ?, c = 3.90 ?.     

Phase diagrams of systems SrF2(Y,Ln)F3. II. Fusibility of systems and thermal behavior of phases

The phase diagrams of 14 SrF₂(Y,Ln)F₃ systems are given, where Ln are all the lanthanides except Pm and Eu. The diagrams have been constructed for temperature intervals from 850°C to the melting points according to the thermal and X-ray analysis. The fusibility diagrams for 12 systems have been obtained for the first time. The oxygen content in the specimens before and after thermal treatment was checked. The thermal behavior of the three types of solid solutions has been studied: (1) with the fluorite-type defective structure and its derivatives; (2) with the defective structure of the lanthanum fluoride, and (3) α-YF₃(α-UO₃) types. Maxima reflecting a noticeable effect of thermal stabilization on the fluorite-type structure by the heterovalent isomorphous substitution have been found for the majority of systems (with Ln = LaHo). The Sr_1?xLn_xF_2+x nonstoichiometric fluorite phases are formed in all the systems. Similar maxima corresponding generally to irrational compositions are present on the fusibility curves of the Ln_1?ySr_yF_3?y nonstoichiometric phases with the LaF₃-type structure (tysonite). Tysonite solid solutions are in all the systems, too. Nonstoichiometric phases with the α-YF₃-type structure are formed in the systems with Ln = ErLu. They are decomposed in the process of cooling and are the most unstable. The structure of the phase diagrams in the regions adjacent to lanthanide trifluorides are determined by polymorphism and morphotropy of the above-named compounds. Changes in the thermal stability of the nonstoichiometric phases and double chemical compounds in the series of lanthanides have been observed. The SrF₂(Y,Ln)F₃ systems studied give examples of the formation of phases with the highest concentrations of point defects among all the known binary fluoride systems (up to 50 at.%). The thermal stabilization effect of the nonstoichiometric phases with the fluorite structure results in the fact that the series of the two-component compositions is melted at considerably higher temperatures as compared with scandium fluoride, the most refractory single-component fluoride compound. This effect leads to formation of tysonite-type solid solutions with melting points exceeding 1500°C (mp of LaF₃—the most refractory fluoride material with tysonite-type structure).     

Amidation of esters assisted by Mg(OCH3)2 or CaCl2

Magnesium methoxide (Mg(OCH₃)₂) and calcium chloride have been shown to facilitate the direct aminolysis of esters by ammonia to primary amides. Methyl, ethyl, isopropyl, and tert-butyl esters were converted to the corresponding carboxamides in good yields. Reactions have been run on a larger scale and without the safety liability inherent in the use of magnesium nitride (Mg₃N₂). Ammonium chloride and amine hydrochlorides have been used successfully in the place of ammonia with magnesium methoxide.     

NaF-NaBr-Na2MoO4 and KF-KCl-KBr ternary systems

Phase equilibria in the NaF-NaBr-Na₂MoO₄ and KF-KCl-KBr have been investigated by differential thermal and X-ray powder diffraction analyses. In the NaF-NaBr-Na₂MoO₄ system, a ternary eutectic and a ternary peritectic, melting and 506 and 570°C with specific enthalpy of melting of 241 and 328 kJ/kg, respectively, have been revealed. In the KF-KCl-KBr system, the existence of zonal solid solutions has been established; crystallization temperatures and melting enthalpies have been determined for samples of several compositions lying on a univariant line. Original Russian Text ? N.N. Verdiev, P.A. Arbukhanova, E.G. Iskenderov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 1, pp. 129–134.     

Phase diagrams of (R4N)2[Nd(NO3)5]-decane-n-octanol (n-butanol, n-decanol) liquid ternary systems

Phase diagrams on the mole fraction scale are presented for decane- (R₄N)₂[Nd(NO₃)₅]-n-octanol(n-butanol, n-decanol) (1–2–3) ternary liquid systems, where R₄N⁺ stands for trialkylbenzylammonium, at T = 298.15 K. The C₁₀H₂₂-(R₄N)₂[Nd(NO₃)₅] binary system is a two-phase liquid system. One phase (phase I) is the almost neat solvent; the other (phase II) is enriched in (R₄N)₂[Nd(NO₃)₅]. The liquid ternary systems are characterized by homogeneous and two-phase liquid solution fields. One phase is enriched in (R₄N)₂[Nd(NO₃)₅] and n-octanol (n-butanol, n-decanol) and the other in C₁₀H₂₂. The miscibilities in the C₁₀H₂₂-(R₄N)₂[Nd(NO₃)₅] binary system and in the ternary liquid systems were used to calculate, from the equations of the nonrandom two-liquid model (NTRL), intermolecular interaction parameters and excess Gibbs free energies g ^E for the binary and ternary liquid systems along the binodal curve. g ^E > 0 is characteristic of the systems under study, while g ^E decreases in the series of pairs of liquids (1, 2), (1, 3), and (2, 3) Original Russian Text ? A.K. Pyartman, V.A. Keskinov, P.V. Zaitsev, N.A. Charykov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 8, pp. 1392–1397.     

Phase formation in Cs2MoO4-MMoO4-Zr(MoO4)2 (M = Mn, Mg, Co, Zn) systems and crystal structure of new double molybdates Cs2MnZr2(MoO4)6 and Cs2MnZr(MoO4)4

Subsolidus phase relations in the Cs₂MoO₄-MMoO₄-Zr(MoO₄)₂ (M = Mn, Zn) ternary systems were determined, and two groups of new isostructural triple molybdates were synthesized: Cs₂MZr(MoO₄)₄ and Cs₂MZr₂(MoO₄)₆ (M = Mn, Mg, Co, Zn). Cs₂MnZr₂(MoO₄)₆ and Cs₂MnZr(MoO₄)₄ crystals were grown by spontaneous flux crystallization and used in structure solution for both groups of compounds. The Cs₂MnZr₂(MoO₄)₆ structure (a =13.4322(2) ?, c = 12.2016(3) ?, group R3, Z = 3, R = 0.0367) is a new structure type characterized by a mixed three-dimensional framework built of corner-sharing MoO₄ tetrahedra and (M, Zr)O₆ octahedra where large channels are occupied by cesium cations. Cs₂MnZr₂(MoO₄)₄ (a =5.3890(1) ?, c = 8.0685(3) ?, space group P $ \bar 3 $ \bar 3 m1, Z = 0.5, R = 0.0247) has the layered glaserite-like KAl(MoO₄)₂ type structure, where Al³⁺ octahedral positions are randomly occupied by a 0.5M²⁺ + 0.5Zr⁴⁺ mixture.     

Phase diagrams of the SrF2(Y,Ln)F3 systems part I.—X-ray characteristics of phases

The phase equilibria in the subsolidus part of 14 binary systems of SrF₂(Y, Ln)F₃ type (Ln—all lanthanides except Pm and Eu) were studied at temperatures over 850°C in equilibrated and quenched specimens by the X-ray analysis method. The oxygen concentration in the specimens before and after the thermal treatment was checked. The crystallographic characteristics of phases formed in the systems i.e. nonstoichiometric phases Sr_1?xLn_xF_2+x with fluorite type structure, phases with fluorite derived type structure, nonstochiometric phases Ln_1?ySr_yF_3?y with tysonite (LaF₃) type structure are given in this paper.