卷 42, 编号 4 (2016)

A series of Sr_1–xBa_xBi₂B₂O₇ solid solutions (x = 0–1) have been synthesized by crystallization from glass ceramics. The crystal structures of solid solutions at x = 0.65 and x = 1 were solved by direct methods of X-ray diffraction from single crystal data and refined in a reduced cell (\({a_{Ba}}{\kern 1pt} = {a_{Sr}}/\sqrt 3 \)) relative to SrBi₂B₂O₇ in the same space group P6₃. Using the Rietveld method, the phase transition range at x = 0.65–0.70 with a reduction of the unit cell has been revealed. As was shown by method of high-temperature powder X-ray diffraction, the solid solutions demonstrated an anisotropic thermal expansion (TE) upon heating in air.

The influence of the target operation mode on the chemical composition and crystalline structure of copper oxide films deposited onto a quartz glass substrate has been studied using Raman spectroscopy and X-ray phase analysis. The films have been synthesized in an Ar + O₂ gaseous environment using two identical magnetrons, differing only by the method of target cooling.

Using differential thermal analysis, X-ray phase analysis, electron microscopy, and optical microscopy, surface nucleation of crystals in glass, obtained from metallurgical slags with the addition of SiO₂, is studied. It is shown that the main phases, crystallized from the surface of the samples are melilite (solid solution of gehlenite 2СаО · Al₂O₃ · SiO₂ in akermanite 2СаО · МgO · 2SiO₂) and diopside (CaO · МgO · 2SiO₂). The kinetics of the crystallization of glass is studied and the rates of the surface crystal growth are determined in the glass of nine compositions. The influence of the degree of dispersion of the particles of the original glass on the deposition order of the crystalline phases and the degree of crystallinity of the glass is studied.

The data on changes in light scattering intensity with time at 330°C after stabilization of the sample at 200°C were obtained using the temperature jump method. It was found that the time dependence of the polarized component at 330°C can be divided into two stages. The first stage involves the initial times and is characterized by the formation of the maximum, which corresponds to the universal effect caused by the emergence of a peak of intensity in the glass-transition interval of oxide glass. The second stage is associated with a decrease in intensities with the characteristic times being significantly longer than the structural relaxation times. The anisotropic scattering intensity was found to increase during low-temperature stabilization at 200°C, while the isotropic scattering intensity remained constant. The behavior of intensity became nonergodic as a result of the long-term heating of the sample: the intensity started to depend on the position of the scattering volume. It was demonstrated that the shape of the fleck from the primary light beam that has passed through the sample can be significantly changed and acquire a speckle structure. A hypothesis was put forward that the detected features in the behavior of light scattering intensity are associated with the development of large-scale structures in the glass volume.

The possibility of applying the method of microwave synthesis for the fabrication of nanosized particles of complex oxides has been demonstrated. The effect of fabrication conditions on the size of nanoparticles with a garnet structure has been established on the example of the Gd–Ga–Al–O system. The concentration of the organic solvent for obtaining particles of an average size of 50 nm has been determined experimentally. The phase composition of thermally treated samples has been investigated. The optimal conditions of producing nanosized powders of garnets, Gd₃(Ga,Al)₅O₁₂, have been determined.

The properties of hydrosols (brand Ludox) are studied by dynamic light scattering (photon correlation spectroscopy, PCS) and colorimetric analysis (formation of a colored β-silicomolybdate complex, KMK). Experimental sol samples for silicate modulus M = 50.0 and М = 3.0 M (M = [SiO₂]/[Me₂O], mol/mol) are obtained by introducing an alkali metal hydroxide (Me). According to the PCS data, the hydrodynamic radius of the sol particles (\({C_{Si{O_2}}}\)= 41.0 g/L) is r = 8.0 nm and increases with the dilution of the sol. These particles’ radii r_∞ (at \({C_{Si{O_2}}}\) → 0) for the initial sol are r_∞ = 13.8 nm and r_∞ = 16.8 nm in sols with alkali metal hydroxides (M = 50). The conjugated phase properties (silica particles and aqueous solution) were considered in the light of polycondensation and depolymerization kinetic reactions involving reactive silicate anions (HO)₃SiO^– and Si(OH)₄) on the surface of the particles and in the composition of soluble fractions. The result is the formation of surface layers of a gel-like structure. With the introduction of alkali metal hydroxides, the initial dissolution rate increases in the range from LiOH to KOH. The existence of peaks in the kinetic dependences of the active silica fractions in highly alkaline environments (M = 50 and M = 3.0) characterizes the secondary polycondensation of silicic acid in the aqueous phase, resulting in the formation of the oligo- and polymeric molecules of a linear structure.

The results obtained by treating porous high-silica glass with ammonium molybdate are reported. The structural changes occur both in the pore space and on the surface of the porous glass.