Glass formation region and order of formation of crystalline phases in the SrO-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> system

The glass formation region in the SrO-B₂O₃-SiO₂ system has been refined. The order of formation of crystalline phases in the system has been investigated at SrO contents of 50–75 mol %. It has been demonstrated that, at low temperatures, the 2SrO · SiO₂ and 3SrO · B₂O₃ phases crystallize first irrespective of the composition. The congruent melting temperature of the 3SrO · B₂O₃ · SiO₂ compound is determined to be 1180 ± 10°C. The triangulation previously performed for the SrO-B₂O₃-SiO₂ system in the concentration range 50–75 mol % SrO has been confirmed.     

Combustion and structure formation in the Ti-Ta-C-Ca<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript> system

Biocompatible composites (Ti, Ta)C _x + Ca₃(PO₄)₂ for deposition of nanofilms onto load-bearing implants by ion-plasma sputtering were prepared from Ti + Ta + C + Ca₃(PO₄)₂ mixtures by forced SHS compaction. The effect of Ta + C addition to green mixtures (characterized by parameter z) on the structure/phase formation in combustion products was explored. The addition of tantalum and carbon was found to have little or no influence on the burning velocity U and combustion temperature T _c. Two thermal spikes exhibited by thermograms were associated with the occurrence of two consecutive reactions leading to formation of titanium and tantalum carbides. With increasing z, the grain size of (Ti, Ta)C was found to diminish, its relative density to decrease, while the hardness to markedly grow.      

Glass formation and the phase diagram of crystalline components in the Sb<Subscript>2</Subscript>S<Subscript>3</Subscript>-PbI<Subscript>2</Subscript> system

Glasses in the Sb₂S₃-PbI₂ system are synthesized, and their physicochemical properties are investigated. The glasses possess high refractive indices (up to 3 or greater). The phase diagram of the Sb₂S₃-PbI₂ system is constructed from the data of differential thermal and X-ray powder diffraction analyses. The diagram exhibits an eutectic behavior. The eutectic is located at a content of 47 mol % PbI₂ and at a temperature of 370 ± 5°C.Original Russian Text Copyright © 2004 by Fizika i Khimiya Stekla, Samoilenko, Mohammad Arif, Novikov, Filatov, Blinov.     

Glass formation and electrical conductivity of glasses in the Na<Subscript>2</Subscript>Se-P<Subscript>2</Subscript>Se<Subscript>5</Subscript> system in a wide temperature range

The glass formation region in the Na₂Se-P₂Se₅ system and the temperature-concentration dependences of the electrical conductivity of glasses have been investigated over a wide range of temperatures. The densities and glass transition temperatures T _g of glasses have been determined. A comparison of the electrical conductivity of glasses in the Na₂Se-P₂Se₅ and Na₂O-P₂O₅ systems has demonstrated that the conductivity of selenium-containing glasses (at 25°C) is approximately three orders of magnitude higher than the electrical conductivity of oxide glasses. The assumption has been made that an increase in the electrical conductivity of glasses with selenium is caused by the increase in the degree of dissociation of Na⁺[Se⁻PSe_3/2] polar structural chemical units and the higher mobility of sodium ions in the oxygen-free matrix.     

Structure and properties of glasses in the MgSO<Subscript>4</Subscript>-Na<Subscript>2</Subscript>B<Subscript>4</Subscript>O<Subscript>7</Subscript>-KPO<Subscript>3</Subscript> system

A glass formation region has been established in the MgSO₄-Na₂B₄O₇-KPO₃ system. This region is located in the borate-phosphate part of the concentration triangle and occupies ∼40% of the triangle area. Based on the spectral data obtained (nuclear magnetic resonance, IR and Raman spectroscopy), a model is proposed in terms of which the physicochemical properties (such as the linear thermal expansion coefficient, the softening temperature, and the glass transition temperature) of the samples are discussed.     

Phase equilibria in the Ho<Subscript>2</Subscript>O<Subscript>3</Subscript>-SrAl<Subscript>2</Subscript>O<Subscript>4</Subscript> system

The phase formation is investigated and the phase diagram of the Ho₂O₃-SrAl₂O₄ system is constructed. A ternary compound, namely, Ho₂SrAl₂O₇, is revealed. It is established that this compound undergoes incongruent melting.     

Phase equilibria in the LaAlO<Subscript>3</Subscript>-LaSrAlO<Subscript>4</Subscript> system

The phase equilibria are investigated and the phase diagram is constructed for the LaAlO₃-LaSrAlO₄ pseudobinary join of the La₂O₃-SrO-Al₂O₃ ternary oxide system. One ternary compound, namely, La₂SrAl₂O₇, is found in the LaAlO₃-LaSrAlO₄ join. The crystallographic, thermal, and some other physicochemical characteristics of the compounds are reported.Original Russian Text Copyright © 2004 by Fizika i Khimiya Stekla, Popova, Tugova, Zvereva, Gusarov.     

Investigation into the phase formation in the ZrO<Subscript>2</Subscript>-CeO<Subscript>2</Subscript> system

Nanopowders of solid solutions with different compositions are prepared in the zirconia-enriched region of the ZrO₂-CeO₂ system. The crystallization of these powders and the formation of the monoclinic, cubic, and tetragonal solid solutions of the composition (Zr_{1 – x} Ce_x)O₂ are investigated. It is found that the unit cell parameters of the solid solutions increase as the cerium content increases. This confirms the fact that cerium ions [r(Ce⁴⁺) = 1.11 ] substitute for zirconium ions [r(Zr⁴⁺) = 0.98 ] in these solid solutions. The average size of crystallites of the solid solutions under investigation increases from 5 to 60 nm in the temperature range 500–1200°C.Original Russian Text Copyright © 2005 by Fizika i Khimiya Stekla, Panova, Glushkova, Nefedova.     

Crystallization and thermal transformations in nanocrystals of the YPO<Subscript>4</Subscript>-LuPO<Subscript>4</Subscript>-H<Subscript>2</Subscript>O system

Nanocrystals of yttrium lutetium phosphates of the general formula Y_1?x Lu_xPO₄ · nH₂O are synthesized. The temperature dependence of the nanocrystal size is investigated in the range 200–1100°C. The formation of a series of continuous solid solutions belonging to the tetragonal crystal system is revealed, and the limits of their thermal stability are determined.     

Preparation and thermal transformations of nanocrystals in the LaPO<Subscript>4</Subscript>-LuPO<Subscript>4</Subscript>-H<Subscript>2</Subscript>O system

Powders of nanosized particles of individual and mixed lanthanum and lutetium orthophosphates are synthesized. The grain growth process is studied in the temperature range of 200–1100°C. Temperature and concentration regions of existence of the solid solutions based on hexagonal and monoclinic forms of LaPO₄ as well as on tetragonal LuPO₄ are determined.     

Thermal behavior of layered perovskite-like compounds in the Bi<Subscript>4</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript>-BiFeO<Subscript>3</Subscript> system

The thermal properties of compounds of the general formula Bi _{m + 1} Fe _{m ? 3} Ti₃O_{3m + 3}, which are layered perovskite-like phases of the Aurivillius type, are investigated as a function of their composition. It is demonstrated that the temperature of decomposition of the Bi _{m + 1} Fe _{m ? 3} Ti₃O_{3m + 3} compounds decreases with an increase in the thickness of perovskite-like layers alternating in the structure and that the composition dependence of the temperature of the structural transition observed in these compounds exhibits a more complex behavior. The linear thermal expansion coefficients of all the compounds under investigation are found to be virtually independent of the composition.     

Structure and electrical conductivity of glasses in the Na<Subscript>2</Subscript>O-Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> system

The temperature-concentration dependence of the electrical conductivity of glasses in the Na₂SO₄-NaPO₃ and Na₂O-P₂O₅ systems has been investigated. Based on the obtained experimental data (IR spectra, density, microhardness, sound velocity, and paper chromatography), it has been demonstrated that SO₄²⁻ ions form terminal groups through the incorporation into polyphosphate fragments of the structure of glasses in the Na₂SO₄-NaPO₃ system. An increase in the electrical conductivity of glasses in this system by a factor of ∼1000 (as compared to NaPO₃) at 25°C and a decrease in the activation energy for electrical conduction from 1.40 to 1.10 eV have been interpreted from the viewpoint of the decrease in the dissociation energy E _d of polar sulfate phosphate structural chemical fragments formed in the glass bulk upon introduction into sodium metaphosphate Na₂SO₄. This leads to an increase in the number of dissociated sodium ions, which are charge carriers, and to a decrease in the energy (E _a) of their activation shift in the sublattice formed by sulfate phosphate fragments of the structure.     

Kinetics of the nanocrystal formation in the ZrO<Subscript>2</Subscript>-In<Subscript>2</Subscript>O<Subscript>3</Subscript>-H<Subscript>2</Subscript>O system under hydrothermal conditions

The hydrothermal synthesis of nanocrystals in the ZrO₂-In₂O₃-H₂O system is investigated kinetically. The presence of indium hydroxide results in an increase in the dehydration temperature of this system. The size of nanocrystals is equal to 20–30 nm and virtually does not depend on the temperature and time of hydrothermal treatment or on the type of crystalline modification of ZrO₂. An increase in the synthesis temperature leads to an increase in the fraction of the monoclinic zirconia modification.Original Russian Text Copyright © 2005 by Fizika i Khimiya Stekla, Artamonova, Almjasheva, Mittova, Lavrushina, Gusarov.     

Synthesis,mutual solubility,and thermal behavior of nanocrystals in the LaPO<Subscript>4</Subscript>-YPO<Subscript>4</Subscript>-H<Subscript>2</Subscript>O system

Nanopowders of lanthanum and yttrium orthophosphates have been synthesized. The growth of nanocrystals has been investigated in the temperature range 200–1100°C. The temperature-concentration limits of the existence of the solid solutions have been determined. The thermal behavior of the orthophosphates has been studied over the entire range of lanthanum and yttrium concentrations.     

Physicochemical and optical properties of glasses in the Ga<Subscript>4</Subscript>Ge<Subscript>21</Subscript>Se<Subscript>50</Subscript>-Sb<Subscript>2</Subscript>Se<Subscript>3</Subscript> system

This paper reports on the results of an investigation into the concentration behavior of the glass-forming ability, heat resistance, glass transition temperature, density, refractive index, transparent spectral region, and impurity optical absorption of glasses in the Ga₄Ge₂₁Se₅₀-Sb₂Se₃ system. The data obtained indicate that glasses in the Ga₄Ge₂₁Se₅₀-Sb₂Se₃ system with a high Sb₂Se₃ content are of interest as materials for use in fiber optics.     

Nonionic polymeric surfactant template for mesoporous NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> formation

Mesostructured NiCo₂O₄ is synthesized in presence of nonionic glucose based polymeric surfactant, β-C₁₀Alkyl Poly Glucoside (β-C₁₀APG). Formed NiCo₂O₄ mesostructures have pore size in the range of 25–65 Å and surface area of 202.9 m²/g. Formed particles are rod shape with 2d hexagonal pattern and Fd3m space group point symmetry. The formation of mesostructure phase is explained by coordination bond formation between metal ions with surfactant head. β-C₁₀APG has the potential to be explored as green template for mesopore formation.     

Investigation of the formation of the GdSrFeO<Subscript>4</Subscript> oxide

The process of phase formation of the complex perovskite-like oxide GdSrFeO₄ at a temperature of 1300°C is investigated. The dependence of the phase composition and the chemical environment of iron atoms on the synthesis time is determined using X-ray powder diffraction and Mössbauer spectroscopy.     

Properties of a melt of the eutectic composition in the NaPO<Subscript>3</Subscript>-Na<Subscript>2</Subscript>B<Subscript>4</Subscript>O<Subscript>7</Subscript>-LiF system

Physical (density, viscosity) and thermophysical (heat capacity, thermal conductivity) properties of a melt of the eutectic composition (wt %) 84NaPO₃ · 8Na₂B₄O₇ · 8LiF have been investigated. It has been demonstrated that this eutectic mixture is a promising material for the use as a high-temperature heat-transfer agent.