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[en] Phase equilibria in the MgMoO₄-Ln₂(MoO₄)₃ systems (Ln=La, Gd) have been studied by static and dynamic methods of the physico-chemical analysis, using differential thermal, visual-polythermal, crystal-optical, X-ray phase, and infrared spectroscopic methods, and their phase diagrams have been constructed. Phase equilibria in the systems studied are characterized by limited solubility of components in the liquid state, formation of solid solutions on the base of α- and β-forms of Gd₂(MoO₄)₃. Eutectics in the MgMoO₄-Ln₂(MoO₄)₃ (Ln=La, Gd) systems corresponds to the composition of 71 mode % La₂(MoO₄)₃-29 mole % MgMoO₄, tsub(melt)--935+-5 deg C and 57 mole % Gd₂(MoO₄)₃-43 mole % MgMoO₄, tsub(melt)=1020+-5 deg C. The region of glass formation has been established

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[en] Phase equilibria in the MgMoO₄-Ln₂MoO₆ (Ln=Sm, Yb, La) systems have been studied by static and dynamic methods of the physico-chemical analysis. It has been ascertained that the investigated systems, excluding the MgMoO₄-La₂MoO₆ system, are quasi-binary and fall into the eutectic type with segregation. Eutectic between MgMoO₄ and Sm₂MoO₆ corresponds to the composition of 19 mol% Sm₂MoO₆-81 mol% MgMoO₄ and 1170+-5 deg C. Yb₂MoO₆ with MgMoO₄ form at 1260+-5 deg C the eutectic of 12 mol% Yb₂MoO₆-88 mol% MgMoO₄ composition. The MgMoO₄-La₂MoO₆ system is a complex cross-section of the ternary MgO-MoO₃-La₂O₃ system. The segregation is observed in this cross-section; the following phases are in the equilibrium in the subsolidus region: LaMoO₆, La₂Mo₂O₉, MgO (the initial content of La₂MoO₆ in the composition exceeds 50 mol%); La₂Mo₂O₉, MgO and MgMoO₄ (samples containing less than 50 mol% LaMoO₆)

[en] Using the methods of the dynamic and static physicochemical analyses in the range of 1073 K-melting temperature the phase equilibria are studied and phase diagram of the BaMoO₄-Lu₂(MoO₄)₃ system is built. The formation of the compound of the composition BaLu₂(MoO₄)₃ incongruently melting at 1393 K and forming limited solid solutions on the basis of BaMoO₄ and Lu₂(MoO₄)₃ are established

[en] The compounds of the composition BaLn₂(MoO₄)₄ have been synthesized and their properties described (Ln=La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu and Y). It has been shown by infrared spectroscopy, X-ray diffraction and thermography that the synthesized compounds crystallize in three different structure types. Molybdates of Pr, Nd, Sm, Eu, Gd, Dy, and Lu refer to the first type; the second type comprises the molybdates of Ho, Er, Tm, Yb, or Y; the third type includes only one compound BaLa₂(MoO₄)₄. The existence of the compounds of the composition BaLn₂(MoO₄)₄ has been proved experimentally for the whole lanthanide series and Y. The relation between the properties and structure of the compounds and the nature of the lanthanide has been shown. It has been demonstrated that in each structure type the properties of the compounds are in a functional dependence from the atomic number of r.e.e

[en] Using the methods of dynamic and static physicochemical analyses phase equilibria in the systems BaMoO⁴-Ln²(MoO⁴)³, where Ln=Nd, Gd, are studied. It is established that state diagrams of the systems are attributed to distectic type with the formation of double molybdate of the composition BaLn²(MoO⁴)⁴, melting congruently. It is shown that in the systems studied solid solutions on the basis of BaMoO⁴, BaLn²(MoO⁴)⁴ and Ln²(MoO⁴)³ are formed

[en] The MgMoO₄ - Sm₂(MoO₄)₃ and MgMoO₄ -Yb₂(MoO₄)₃ systems are investigated using static and dynamic methods of physicochemical analysis. The region of solid solutions on the basis of r.e.e. molybdate is established in the systems as well as the presence of liquation. By hardening Sm₂(MoO₄)₃ from 1150 deg C γ-modification of samarium molybdate is obtained (refractive index > 2.05, the biaxial crystals, positive optical mark). The sample annealing at the temperatures 1090-950 and 800 deg C transforms γ-Sm₂(MoO₄)₃ to β- and α-modifications respectively. The results of X-ray phase and infrared spectroscopic investigations fully correlate with the data of optical investigation. The aggregate of the data obtained is reflected at the diagram of the system state. Conclusion is made that the effect of structural types of r.e.e. molybdates on the character of phase equilibria in the MgMoO₄ - Ln(MoO₄)₃ systems is not considerable

[en] Habitus, extinction character, cleavage, optical sign and refractive indices are determined for bismuth niobate crystals obtained by crystallization from melt. The results are compared with the published crystallochemical and optical data. 6 refs., 1 tab

[en] Crystallization of glasses of the system in the title has been studied by thermography, x-ray diffraction phase analysis, crystallochemical analysis, and IR spectroscopy. Formation of crystalline borates, for the most part unknown from literature, is ascertained. All, or practically all liberating phases did not contain fluorine. Data obtained support the proceeding of exchange interactions in the molten system that results in substitution of considerable part of oxygen atoms in yttrium surroundings for fluorine