V. E. Shukshin

Raman spectra and structure of silicon-oxygen groups in crystalline, liquid, and glassy Mg2SiO4

We have measured the Raman spectra of magnesium orthosilicate at temperatures from 300 to 2170 K and have shown that liquid magnesium orthosilicate can be supercooled to 1600 K and can be prepared in the form of glass at quenching rates above 400 K/s. Analysis of Raman results indicates that, in contrast to crystalline Mg2SiO4, liquid and glassy magnesium orthosilicate contains not only isolated [SiO4]4− groups but also polymerized anions made up of corner-shared [SiO4] tetrahedra. This accounts for the observed deep (down to 600 K) supercooling and vitrification of liquid magnesium orthosilicate. During cooling, large [SiO4] groups have a tendency to depolymerize, and the concentration of isolated [SiO4]4− tetrahedra in the super-cooled magnesium orthosilicate melt increases, leading to spontaneous crystallization below 1550 K.

Barium borate glass and transparent glass ceramics doped with Pb4Lu2YbF17

Barium borate glasses doped with complex Pb4Lu2YbF17 fluoride have been synthesized and investigated. Heat treatment produced glass ceramics containing the crystalline BaF2:Yb3+ phase. The changes in the structural and optical properties of the glass ceramics were revealed by X-ray diffraction, Raman spectroscopy, and luminescence spectroscopy of Yb3+ ions in polycrystalline Pb4Lu2YbF17, initial glass, and glass ceramics.

Synthesis of scandium orthoborate powders

Two polymorphs of scandium orthoborate, ScBO3, are synthesized by adding aqueous ammonia to aqueous solutions of scandium nitrate and boric acids and calcining the resulting precipitates. Dehydration of the precipitates reaches completion below 300°C, and further heating leads to highly exothermic crystallization near 750°C. The synthesized ScBO3 powders consist of submicron-sized particles.

Spectroscopy of Disordered Laser Crystals

The nonuniform broadening of optical spectra is analyzed for two types of rare-earth-activated disordered laser crystals: substituted garnets and yttria-stabilized zirconia (ZrO2–Y2O3). By decomposing nonuniformly broadened, composite R3+ absorption and luminescence bands, several principal centers (K and L for Eu3+ andA, B, C, and D for Nd3+) are identified and correlated with particular configurations of the near-neighbor environment of the activator ions (optical centers). It is shown that the formation of activator associates has a weaker effect on the optical spectra than the nearest neighbor coordination of the activator.

Growth and Spectroscopic Study of Yb3+-Activated YVO4 Crystals

The absorption and luminescence spectra of Yb3+ and the luminescence decay kinetics for the Yb3+2F5/2 level in YVO4:Yb3+ crystals are studied. The luminescence cross section for the Yb3+2F5/2 → 2F7/2transition in YVO4:Yb3+ is determined by the Füchtbauer–Ladenburg method, and the radiative lifetime of Yb3+ is evaluated.

Raman scattering in LiB3O5 single crystals at 300 and 20 K

The Raman-scattering spectra of LiB3O5 single crystals at 300 and 20 K have been investigated in detail. The LO- and TO-phonon lines of different symmetries are separated and identified. The reasons for the change in the Raman spectra of LiB3O5 upon cooling to 20 K are studied. The intensity ratios for scattering with participation of LO and TO modes of the A1 symmetry are found in dependence on the observation geometry.

Raman spectroscopy of SrB4O7 single crystals in the temperature range 300–1273 K

The polarized Raman spectra of SrB4O7 (SBO) single crystals are studied in detail in the temperature range of 300–1273 K. The TO, LO, and IO phonon lines of A1, A2, B1, and B2 symmetries of rhombic SBO at 300 K are identified. The behavior of the Raman spectra of SBO crystals is studied upon heating up to their melting. The relation of Raman spectra with the structure of boron–oxygen fragments, as well as the transformation of spectra in the process of melting of SBO crystals, is discussed.

Study of Raman spectra in the processes of glass formation, crystallization, and melting of strontium diborate

The behavior of the Raman spectra of SrB4O7 (SBO) and Li2B4O7 crystals upon melting and glass formation is studied by high-temperature Raman spectroscopy (HTRS). The character of formation of boron–oxygen fragments in different aggregate states of SBO is discussed based on an analysis of the Raman spectra in the crystalline, glassy, and molten states.

Spectroscopic studies of glasses based on rare-earth borates

Raman light scattering and Nd3+ luminescence are investigated in glasses based on rare-earth borates with a high content of the rare-earth oxide and subjected to annealing. It is established that, during annealing, structural relaxation brings about the formation of phases with a structure similar to the structure of rare-earth orthoborates and oxoborates. This leads to considerable changes in the characteristics of Nd3+ luminescence.

Raman spectroscopy of crystalline, glassy, and molten states of lead diborate

Polarized Raman spectra of single crystals of lead diborate, PbB4O7 (PBO), are studied in detail at 300 K. The TO-, LO-, and IO-phonon lines of the A1, A2, B1, and B2 symmetries in the Raman spectra of this compound are assigned. Changes in the Raman spectra of the internal vibrations of boron–oxygen complexes upon transition from the crystalline to the glassy and the molten states of PBO are observed. On the basis of the obtained results, the regularities in the formation of boron–oxygen complexes in glasses, melts, and crystals of the PbO · 2B2O3, SrO · 2B2O3, and Li2O · 2B2O3. diborate compositions are analyzed.