NaBO2-NaCl-Na2CO3, NaBO2- Na2CO3-NaMoO4, NaBO2- Na2CO3-NaWO4, and NaBO2-NaCl-Na2WO4 ternary systems

The phase diagrams of the NaBO₂-NaCl-Na₂CO₃, NaBO₂-Na₂CO₃-Na₂MoO₄, NaBO₂- Na₂CO₃-Na₂WO₄, and NaBO₂-NaCl-Na₂WO₄ ternary systems were studied by a calculation-experimental method and differential thermal analysis. The coordinates of ternary eutectics were determined: E ₁: 612°C, 16 mol % NaBO₂, 42 mol % NaCl, and 42 mol % Na₂CO₃; E ₂: 568°C, 12 mol % NaBO₂, 28 mol % Na₂CO₃, and 60 mol % Na₂MoO₄; E ₃: 575°C, 12 mol % NaBO₂, 32 mol % Na₂CO₃, and 56 mol % Na₂WO₄; E ₄: 628°C, 8 mol % NaBO₂, 20 mol % NaCl, and 72 mol % Na₂WO₄; and E ₅: 655°C, 9 mol % NaBO₂, 53 mol % NaCl, and 38 mol % Na₂WO₄.     

NaCl-NaBO2-Na2CO3-NaMoO4 quaternary system

The NaCl-NaBO₂-Na₂CO₃-Na₂MoO₄ quaternary system was studied by a calculation-experimental method and differential thermal analysis. The coordinates of one ternary eutectic and two quaternary eutectics were determined: E ₇: 572°C, 29 mol % NaCl, 10 mol % NaBO₂, 32 mol % Na₂CO₃, and 29 mol % Na₂MoO₄; ɛ₁: 562°C, 36 mol % NaCl, 10 mol % NaBO₂, 30.5 mol % Na₂CO₃, and 23.5 mol % Na₂MoO₄; and ɛ₂: 536°C, 17 mol % NaCl, 10 mol % NaBO₂, 27 mol % Na₂CO₃, and 46 mol % Na₂MoO₄.     

Phase equilibria in the KCl-KBO2-K2CO3-K2WO4 quaternary system

The phase diagram of the KCl-KBO₂-K₂CO₃-K₂WO₄ quaternary system was studied by a calculation-experimental method and differential thermal analysis. Analytical models of phase equilibrium states were obtained, and the coordinates of a quaternary eutectic were determined: 545°C, 50 mol % KCl, 8 mol % KBO₂, 22.5 mol % K₂CO₃, and 19.5 mol % K₂WO₄.     

Phase equilibria in the KCl-KBO2-K2CO3-K2MoO4 quaternary system

The phase diagram of the quaternary system KCl-KBO₂-K₂CO₃-K₂MoO₄ was studied by a calculation-experimental method and differential thermal analysis. Analytical models of phase equilibrium states were obtained, and the coordinates of a quaternary eutectic were determined: 550°C, 50% KCl, 8% KBO₂, 23% K₂CO₃, and 19% K₂MoO₄.     

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.     

Interaction of salts in ionic melts of the ternary reciprocal systems Na,K‖BO2,MoO4 and Na,K‖BO2,WO4

The phase diagrams of the ternary reciprocal systems Na,K‖BO₂,MoO₄ and Na,K‖BO₂,WO₄ were studied for the first time by a calculation-experimental method and differential thermal analysis. The coordinates were determined for binary eutectics of the diagonal stable sections NaBO₂-K₂MoO₄(K₂WO₄) and the ternary invariant points e(55 mol % NaBO₂, 45 mol % K₂MoO₄, 740°C), e(55 mol % NaBO₂, 45 mol % K₂WO₄, 730°C), E(4.5 mol % NaBO₂, 78 mol % Na₂MoO₄, 17.5 mol % K₂MoO₄, 652°C), E(4.5 mol % NaBO₂, 78 mol % Na₂WO₄, 17.5 mol % K₂WO₄, 643°C), P₂(5 mol % NaBO₂, 56 mol % Na₂MoO₄, 39 mol % K₂MoO₄, 673°C), P₂(5 mol % NaBO₂, 56 mol % Na₂WO₄, 39 mol % K₂WO₄, 671°C). Binary solid solutions based on sodium and potassium metaborates were shown to be stable. Analytical models of phase equilibrium states of the ternary reciprocal systems Na,K‖BO₂,MoO₄(WO₄) were obtained, which enable one to calculate melting (crystallization) points and construct isotherms at any given composition. The specific heats of melting of samples of invariant compositions were found by quantitative differential thermal analysis.     

Li,K‖Cl,MoO4 ternary mutual system

Phase equilibria in the Li,K‖Cl,MoO₄ ternary mutual system were studied by differential thermal analysis (DTA). The characteristics of the following three ternary eutectics were determined: E ₁: 348°C, 41 mol % KCl, 7.75 mol % Li₂MoO₄, and 51.25 mol % LiCl; E ₂: 475°C, 44 mol % KCl, 17.25 mol % Li₂MoO₄, and 38.75 mol % LiCl; and E ₂: 477°C, 35 mol % KCl, 47 mol % Li₂MoO₄, and 18 mol % LiCl.     

Study of phase equilibria and boundary elements in the KBr-KVO3-K2MoO4 ternary system

By differential thermal analysis, the coordinates of the following characteristic points in the KBr-KVO₃-K₂MoO₄ system were determined: a eutectic in the KBr-KVO₃ system (12% KBr, 88% KVO₃, T _melt = 458°C), a eutectic in the KBr-KVO₃-K₂MoO₄ ternary system (12.8% KBr, 84.7% KVO₃, 2.5% K₂MoO₄,T _melt = 430°C), and also three points of polymorphic transitions in K₂MoO₄ ((1) δ ? γ: 21.7% KBr, 72.3% KVO₃, 6% K₂MoO₄,T _melt = 476°C; (2) γ ? β: 19% KBr, 78% KVO₃, 3% K₂MoO₄,T _melt = 450°C; and (3) γ ? β: 6% KBr, 89% KVO₃, 5% K₂MoO₄,T _melt = 450°C). For elements of the ternary system, phase equilibria were described.     

A new ferroelastic transition in some A2(MO4)3 molybdates and tungstates

We have found for the first time a ferroelastic transition in many molybdates and tungstates with the Sc₂(MoO₄)₃-type structure. Below the transition these phases are monoclinic ($\text{P2}{}_1\text{a}$), and above the transition they are orthorhombic (Pnca). Observed transition temperatures are: Al₂(MoO₄)₃, 200°C; Al₂(WO₄)₃, ?6°C; Cr₂(MoO₄)₃, 385°C; Fe₂(MoO₄)₃, 499°C; In₂(MoO₄)₃, 335°C; In₂(WO₄)₃, 252°C; and Sc₂(MoO₄)₃, 9°C.     

High-temperature equilibria and critical phenomena in the Na2CO3-NaCl-H2O and Na2CO3-Na2WO4-H2O systems

Phase equilibria in the Na₂CO₃-NaCl-H₂O and Na₂CO₃-Na₂WO₄-H₂O ternary systems formed by type 1 salts (NaCl, Na₂WO₄) and a type 2 salt (Na₂CO₃) were experimentally studied at temperatures from 425 to 500°C and pressures from 30 to 160 MPa with the contents of type 1 salts from 10 to 30 wt %. Transition from supercritical homogeneous fluid equilibria of the Na₂CO₃-H₂O system to heterogeneous equilibria of the title ternary systems was studied in the presence or absence of liquid phase immiscibility in the type 1 subsystems.     

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.     

Cr2(WO4)3和Cr2(MoO4)3的负热膨胀特性研究

用液相反应-前驱物烧结法制备了Cr₂(WO₄)₃和Cr₂(MoO₄)₃粉体。298～1 073 K的原位粉末X射线衍射数据表明Cr₂(WO₄)₃和Cr₂(MoO₄)₃的晶胞体积随温度的升高而增大, 本征线热膨胀系数分别为(1.274±0.003)×10^-6 K^-1和(1.612±0.003)×10^-6 K^-1。用热膨胀仪研究了Cr₂(WO₄)₃和Cr₂(MoO₄)₃在静态空气中298～1 073 K范围内热膨胀行为，即开始表现为正热膨胀，随后在相转变点达到最大值，最后表现为负热膨胀，其负热膨胀系数分别为(-7.033±0.014)×10^-6 K^-1和(-9.282±0.019)×10^-6 K^-1。     

LiF-KCl-KVO3-K2MoO4-LiKMoO4 stable pentatope

Phase equilibria in the LiF-KCl-KVO₃-K₂MoO₄-LiKMoO₄ stable pentatope of the Li,K‖F,Cl,VO₃,MoO₄ reciprocal five-component system were studied using differential thermal analysis (DTA). A eutectic was found to have a composition (mol %) of 50.0 LiF, 11.5 KCl, 6.0 KVO₃, 1.6 K₂MoO₄, and 25.0 LiKMoO₄ and a melting temperature of 394°C.     

Phase relations in the K2W2O7-K2WO4-KPO3-Bi2O3 system and structure of K6.5Bi2.5W4P6O34

The phase relations in the cross-section of the K₂W₂O₇-K₂WO₄-KPO₃ containing 15 mol% Bi₂O₃ were undertaken using flux method. Crystallization fields of K_6.5Bi_2.5W₄P₆O₃₄, K₂Bi(PO₄)(WO₄), Bi₂WO₆, KBi(WO₄)₂ and their cocrystallization areas were identified. Novel phase K_6.5Bi_2.5W₄P₆O₃₄ was characterized by single-crystal X-ray diffraction: sp. gr. P−1, a=9.4170(5), b=9.7166(4), c=17.6050(7) Å, α=90.052(5)°, β=103.880(5)° and γ=90.125(5)°. It has a layered structure, which contains {K₇Bi₅W₈P₁₂O₆₈}_∞ layers stacked parallel to ab plane and sheets composed by potassium atoms separating these layers. Sandwich-like {K₇Bi₅W₈P₁₂O₆₈}_∞ layers are assembled from [W₂P₂O₁₃]_∞ and [BiPO₄]_∞ building units, and are penetrated by tunnels with K/Bi atoms inside. FTIR-spectra of K₂Bi(PO₄)(WO₄) and K_6.5Bi_2.5W₄P₆O₃₄ were discussed on the basis of factor group theory.     

Phase relations in the system K2MoO4–KPO3–MoO3–Bi2O3: A new phosphate K3Bi5(PO4)6

Phase equilibrium in the pseudo-quaternary system K₂O–MoO₃–P₂O₅–Bi₂O₃ was studied as three-component solvent K₂MoO₄–KPO₃–MoO₃ containing 15 mol% Bi₂O₃ during slow cooling and spontaneous crystallization. The results of the investigation were shown on a composition diagram, which indicates the crystallization fields of K₂Bi(PO₄)(MoO₄), K₅Bi(MoO₄)₄, BiPO₄ and K₃Bi₅(PO₄)₆. New phosphate K₃Bi₅(PO₄)₆ was characterized by single-crystal X-ray diffraction (space group C2/c, a=17.680(4), b=6.9370(14), c=18.700(4) Å, β=113.79(3)°) and FTIR spectroscopy. The possibility of lone electron pair stereoactivity of bismuth was suggested using the calculations of characteristics of the Voronoi–Dirichlet polyhedra for K₃Bi₅(PO₄)₆ and K₂Bi(PO₄)(MoO₄).     

Phase formation in the systems Li2MoO4-K2MoO4-Ln2(MoO4)3 (Ln=La, Nd, Dy, Er) and properties of triple molybdates LiKLn2(MoO4)4

Subsolidus phase relations in the systems Li₂MoO₄-K₂MoO₄-Ln₂(MoO₄)₃ (Ln=La, Nd, Dy, Er) were determined. Formation of LiKLn₂(MoO₄)₄ was confirmed in the systems with Ln=Nd, Dy, Er at the LiLn(MoO₄)₂-KLn(MoO₄)₂ joins. No intermediate phases of other compositions were found. No triple molybdates exist in the system Li₂MoO₄-K₂MoO₄-La₂(MoO₄)₃. The join LiLa(MoO₄)₂-KLa(MoO₄)₂ is characterized by formation of solid solutions.Triple molybdates LiKLn₂(MoO₄)₄ for Ln=Nd-Lu, Y were synthesized by solid state reactions (single phases with ytterbium and lutetium were not prepared). Crystal and thermal data for these molybdates were determined. Compounds LiKLn₂(MoO₄)₄ form isostructural series and crystallized in the monoclinic system with the unit cell parameters a=5.315-5.145 Å, b=12.857-12.437 Å, c=19.470-19.349 Å, β=92.26-92.98°. When heated, the compounds decompose in solid state to give corresponding double molybdates. The dome-shaped curve of the decomposition temperatures of LiMLn₂(MoO₄)₄ has the maximum in the Gd-Tb-Dy region.While studying the system Li₂MoO₄-K₂MoO₄-Dy₂(MoO₄)₃ we revealed a new low-temperature modification of KDy(MoO₄)₂ with the triclinic structure of α-KEu(MoO₄)₂¹ (a=11.177(2) Å, b=5.249(1) Å, c=6.859(1) Å, α=112.33(2)°, β=111.48(1)°, γ=91.30(2)°, space group , Z=2).     

Binary molybdates K4M2+(MoO4)3 (M2+=Mg, Mn, Co) and crystal structure of K4Mn(MoO4)3

Binary molybdates K₄M²⁺ (MoO₄)₃ (M²⁺=Mg, Mn, Co) isostructural to triclinic \ga-K₄Zn(WO₄)₃ were synthesized, and optimal conditions for their spontaneous crystallization were found. It was established by XRPA and DTA that at 530°C the structure of the compound with cobalt undergoes a transition to the orthorhombic structure of K₄Zn(MoO₄)₃. The structure of K₄Mn(MoO₄)₃ was determined from single crystal diffraction data (a=7.613, b=9.955, c=10.156 Å,α=92.28,β=106.66,γ=105.58°, Z=2, space group $P\bar 1$ , R=0.030). In this compound, Mn has a higher coordination number (CN=5+1) than that of Zn inα-K₄Zn(WO₄)₃ (CN=4+1). The main structural feature is pairs of MnO₆ octahedra linked by the bridging MoO₄ tetrahedra into ribbons stretching along the a axis. The structure is compared with related structures of binary molybdates and other members of the alluaudite family.     

Crystal structure,dimensionality, and 4d electron distribution in K0.30MoO3 and Rb0.30MoO3

Single crystals of K_0.30MoO₃ and Rb_0.30MoO₃ were synthesized by electrolytic reduction of MoO₃/ A₂MoO₄ melts. The crystal structures were refined from X-ray diffraction data (3265 and 1280 independent reflections, respectively). The finalR andwR factors were 0.037 and 0.047 for the K bronze and 0.031 and 0.033 for the Rb bronze. The lattice parameters of the body-centered cells used in the present refinements were: K_0.30Mo0₃,a = 16.2311(7),b = 7.5502(4),c = 9.8614(4)A?,β = 94.895(4)^o; Rb_0.30MoO₃,a = 16.361(3),b = 7.555(1),c = 10.094(2)A?,β = 93.87(5)^o. The 4d electron distribution over the 20 Mo sites [4Mo(1), 8Mo(2), 8Mo(3)] of the unit cell are 10, 45, and 45% for K_0.30Mo0₃ and 14, 43, and 43% for Rb_0.30MoO₃, respectively. In both cases about 90% of the 4d electrons are situated on those sites which contribute to the electrical conductivity. The variations of the lattice parameters versus temperature are reported. The thermal linear-expansion coefficient is highly anisotropic. The structural dimensionality depends upon the sublattice under consideration. The K, Mo, and O sublattices are mono-, two-, and three-dimensional, respectively. The relationship between the structural dimensionality of K_0.30MoO₃ and the physical properties is discussed.     

Crystal Structure of Ternary Molybdate Rb5FeHf(MoO4)6 — a New Phase in the Rb2MoO4-Fe2(MoO4)3-Hf(MoO4)2 System

Physicochemical analysis (XRPA, DTA) was used to study phase equilibria in a ternary salt system Rb₂MoO₄-Fe₂(MoO₄)₃-Hf(MoO₄)₂ in the subsolidus region. Ternary molybdates with compositions 5:1:3, 5:1:2, and 1:1:1 have been found and synthesized. Crystal and thermal characteristics have been determined. Single crystals of the ternary molybdate Rb₅FeHf(MoO₄)₆ with a composition of 5:1:2 were grown. The crystal structure of the compound was solved using X-ray diffractometry (CAD-4 automatic diffractometer, MoK _α radiation, 1766 F(hkl), R = 0.0298). Hexagonal crystals with unit cell dimensions: a = b = 10.124(1) Å, c =15.135(3) Å, V = 1343.4(4) ų, Z = 2, ρ_calc = 4.008 g/cm³, space group P6₃. The mixed three-dimensional framework of the structure is formed from two sorts of MoO₄ tetrahedra and Fe and Hf octahedra linked through their common O-vertices. Rubidium atoms of three varieties occupy the large voids of the framework.Original Russian Text Copyright © 2004 by B. G. Bazarov, R. F. Klevtsova, A. D. Tsyrendorzhieva, L. A. Glinaskaya, and Zh. G. Bazarova__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 1038–1043, November–December, 2004.     

Phase relations,dopant effects,structure, and high electrical conductivity in the Na2WO4Na2MoO4 system

The x, T-phase diagram of the binary system Na₂WO₄Na₂MoO₄ has been redetermined at ambient pressure, taking into account the influence of hysteresis effects. Thermodynamic calculations, based upon transition entropies as determined by precision DSC (differential scanning calorimetry), indicate that the system is almost ideal with respect to the high-temperature phases.As anion dopes, Na₂SO₄ and Na₂CrO₄ give a metastable extension of the β-phase of Na₂WO₄ at decreasing temperature, involving some 40°C at 0.01 mole fraction of dopant. Cation dopes like Li₂WO₄ and K₂WO₄ behave quite differently.The electrical conductivity through the phase diagram is high in the α-phase (σ ～ 10^?2 mho cm^?1) almost regardless of composition. The anomalous high conductivity of the β-phase decreases with increasing molybdate content. In pure Na₂MoO₄ an anomaly occurs at the α-α₂ transition, resembling the behavior of Na₂WO₄ at the β-α transition. The (highest) α₂-phase is hexagonal, ($\text{P6}{}_3\text{mmc}$, showing large anisotropic thermal vibrations. The α-phase is orthorhombic (Fddd) as is the β-phase (probably Pbn2₁).