A. V. Egorysheva

Vibrational Spectra of Crystals of Bismuth Borates

The vibrational spectra of crystals of bismuth borates Bi24B2O39, Bi4B2O9, BiBO3, and Bi2B8O15 were obtained for the first time, and the spectra of Bi3B5O12 and BiB3O6 crystals measured in the range 30–1600 cm−1 at room temperature were refined. The lines observed were assigned to the corresponding vibrational transitions on the basis of the theoretical group analysis and comparison of the obtained results with the vibrational spectra of borates of different composition. The complication of the structure of bismuth borates with increasing content of B2O3 was traced by the example of vibrational spectra.

Glass formation in the Bi2O3-B2O3-BaO system

The physicochemical properties of BaO-Bi2O3-B2O3 glasses have been studied. The effect of KBF4 additions on the properties of the glasses has been examined. The transmission of the glasses has been correlated with their local structure and composition.

Laser Raman Spectroscopy of Crystals with the Structure of Sillenite

The experimental data of the past 10–15 years for the vibrational spectra of crystals with the structure of sillenite Bi12MxO20±δ obtained by the methods of laser Raman scattering and infrared (IR) absorption are generalized. Correlations between the chemical composition and crystal structure of the compounds (variations of the cation M) and their vibrational spectra are established. It is shown that the main contribution to formation of the high‐frequency part of the spectrum of two‐, three‐, and four‐phonon absorption is given by phonons related to vibrations of the [MO4]n- complexes. On the basis of the analysis of Raman spectra, the effective use of crystals with the structure of sillenite in acousto‐optics is justified.

Efficient nonlinear optical material BiB3O6 (BIBO)

This review is devoted to a new nonlinear optical material BiB3O6 (BIBO). It systemizes data on the phase equilibrium, structure, polymorphism, and growth characteristics of single crystals of this compound and considers its main properties and fields of application. The bibliography includes 122 references.

Glass formation in the CaO-Bi2O3-B2O3 and SrO-Bi2O3-B2O3 systems

A physicochemical study of glasses based on the MO-Bi2O3-B2O3 and SrO-Bi2O3-B2O3 systems was performed. Glass formation regions were found. The structural and optical properties, as well as the thermal behavior of the glasses, were studied.

Optical and chiro-optical properties of crystals with sillenite structure

The experimental data on the optical and chiro-optical properties of crystals with the sillenite structure Bi12MxO20 ± δ (M= elements of II–VIII groups) have been reviewed. The relations between the changes in the chemical composition, the crystal structure of Bi12MxO20 ± δ compounds, absorption, circular dichroism, and optical rotation spectra of sillenites have been established. A model taking into account the contribution of the electronic transitions of optically active tetrahedral [MO4]n− complexes to the total optical rotation in sillenites is suggested. The data on the state (oxidation degree) and the recharging processes of 3d-elements in sillenites are systematized. The models of optical centers responsible for the photochromic effect in sillenites are critically analyzed.

Mechanochemical activation of starting oxide mixtures for solid-state synthesis of BiFeO3

We have studied the effect of mechanochemical activation on the reactivity of Bi2O3 + Fe2O3 oxide mixtures, assessed the temperature effect on the kinetics of BiFeO3 formation in the oxide mixtures before and after mechanochemical activation, and optimized the conditions of bismuth ferrite synthesis by solid-state reaction. A material with a BiFeO3 content of at least 98.3 wt % has been obtained, and its magnetic properties have been investigated.

Crystal-structure refinement, thermal expansion, and chemical distortion of Bi2Ga4O9

Single crystals of Bi2Ga4O9 are grown from a solution in a bismuth oxide melt. The structure (orthorhombic, space group Pbam, a = 7.918(2) Å, b = 8.299(2) Å, c = 5.894(2) Å, Z = 2) is refined to R = 0.052 in the anisotropic approximation based on single-crystal X-ray diffraction data. The structure is a framework. The bismuth(III) atoms are sixfold coordinated; gallium(III) exists in both tetrahedral and octahedral coordinations. The thermal expansion of Bi2Ga4O9 is studied by high-temperature X-ray powder diffraction method and is found to be sharply anisotropic. A structural interpretation of the anisotropy is proposed. Chemical distortion in the Bi2M4O9 compounds with M = Fe(III), Al, or Ga is analyzed and compared with the thermal expansion of Bi2Ga4O9.

Phase equilibria in the BaO-Bi2O3-B2O3 system

Phase equilibria in the BaO-Bi2O3-B2O3 system have been investigated by X-ray powder diffraction analysis and DTA. Quasi-binary sections have been determined, and an isothermal section of the system in the subsolidus region has been constructed. The BaO-Bi2O3-B2O3 ternary system has been divided into 22 triangles of coexisting phases. It has been found that four bismuth barium borates exist, namely, Ba3BiB3O9, BaBi2B4O10, BaBiB11O19, and BaBiBO4. Ba3BiB3O9 undergoes a phase transition at 850°C and exists up to 885°C, where it decomposes in the solid state. BaBiB11O19 and BaBi2B4O10 melt congruently at 807 and 730°C, respectively. BaBiBO4 melts incongruently at 780°C. X-ray powder diffraction data for the low-temperature polymorph of Ba3BiB3O9 are presented.

Luminescence of europium-doped BaO-Bi2O3-B2O3 glasses

We have prepared europium-doped BaO-Bi2O3-B2O3 glasses and investigated the doping effect on the main physicochemical properties and local structure of the glasses. Using Judd-Ofelt analysis, we calculated intensity parameters (Ω2, Ω4, and Ω6), spontaneous emission probabilities, the radiative lifetime, luminescence branching factors, the quantum yield of luminescence, and the stimulated emission cross sections for 5D0 → 7FJ transitions.