Potassium–yttrium tungstate single crystals KYb x Y 1– x (WO 4 ) 2 of high structural quality are grown by the modified Czochralski method. The crystals were grown using so-called dynamic growth regime, and optimal temperature gradients at the crystallization front were determined. The thermal expansion coefficients of KYb x Y 1– x (WO 4 ) 2 in the directions of the optical indicatrix axes N p , N m and N g are determined using the dilatometric technique. The dependence of thermal expansion coefficients on the temperature in the range of 330–573 K and ytterbium content x from 0 to 1.0 is discussed.

In this paper the effect of modifying components containing Al2O3, B2O3, SiO2 and CaO introduced in various combinations on high and low-temperature viscosity values of basalt glass has been studied. It is shown that the introduction of boron-containing components in compositions with basalt leads to a significant decrease in the viscosity of the basalt melt at all temperature ranges. Influence of modifiers on low-temperature viscosity values of basalt glass correlates with their influence on high-temperature viscosity. Based on experimental values of rheological properties and crystallization ability of modified basalt melts, the modes of basalt fibre production have been determined.

Potassium–yttrium tungstate single crystals KYbxY1–x(WO4)2 of high structural quality are grown by the modified Czochralski method. The crystals were grown using so-called dynamic growth regime, and optimal temperature gradients at the crystallization front were determined. The thermal expansion coefficients of KYbxY1–x(WO4)2 in the directions of the optical indicatrix axes Np, Nm and Ng are determined using the dilatometric technique. The dependence of thermal expansion coefficients on the temperature in the range of 330–573 K and ytterbium content x from 0 to 1.0 is discussed.

Optical glass ceramics based on oxyfluoride glasses activated by rare earth ions have attractive properties for development of lasers and near-infrared amplifiers, since they combine properties of fluoride crystals with low phonon frequencies and chemical and mechanical properties of oxide matrices. Spectroscopic properties of activator ions in crystalline and glass phases of glass-ceramics can differ significantly. Thus, it is possible to determine impurity ions’ distribution between these phases by means of absorption or luminescence spectra analysis. The main goal of this work was to develop a method for determining the concentration of Tm3+ and Ho3+ ions in the crystalline, PbF2 and glassy phases of glass ceramics after secondary thermal treatment of thulium-doped and thulium-holmium co-doped oxyfluoride glasses. Spectroscopic characteristics of oxyfluoride glasses activated by Tm3+ ions and co-activated by Tm3+ and Ho3+ ions, as well as glass ceramics obtained from the original glasses as a result of secondary heat treatment were studied. It was established by X-ray phase analysis method that under certain heat treatment conditions crystalline β-PbF2 phase is formed in those glasses. Absorption and luminescence spectra of Tm3+ and Ho3+ impurity ions in the original glass and in β-PbF2 crystals were compared with their ones in glass ceramics. A method for determining the concentration of ions in the crystalline and glass phases of glass ceramics was proposed on the basis of this comparison. Dependence of Tm3+ and Ho3+ ions distribution between the glass and crystalline phases on different regime of glasses' secondary heat treatment was studied.

The paper studies the influence that Al2O3, B2O3, SiO2 and CaO containing modifying components introduced in different combinations have on the technological and mechanical properties of basalt glass concerning their use in the production of continuous fibre. It is shown that introduction of boron-containing components into compositions with basalt accelerates achievement of structural homogeneity of the melt and reduces crystallization capacity of the glass. The viscosity and the upper crystallization temperature numbers that determine the technological parameters of fibre formation are determined. The elastic and strength properties of basalt glass were studied under static and cyclic loads. It is established that introduction of modifying aluminium-containing components ensures a 15–30% increase in the strength parameters. The optimal combination of technological and mechanical properties of basalt glass is achieved due to the use of compound modifiers with aluminium- and boron-containing components.

Samples of nanocrystalline PbF2 glass ceramics were obtained by heat-treating SiO2–GeO2–PbO–PbF2–CdF2 glasses. The Ho2O3 and Tm2O3 doping effects on the structural features of PbF2 nanoparticles were studied using small-angle X-ray scattering and X-ray diffraction methods. The enlargements of the average sizes of nanoparticles and the sizes of local areas of density fluctuations have been found to be correlated with an increase in concentrations of Ho2O3 and Tm2O3 in initial glasses. A variation in the concentrations of Ho2O3 and Tm2O3 does not affect the morphology and fractal dimension of the formed PbF2 nanoparticles.

Cerium doped gadolinium gallium aluminum garnet (Gd3Al3Ga2O12, GAGG) was synthesized in the glass ceramics form by the crystallization from Gd2O3–Al2O3–Ga2O3–SiO2–CeO2 glass in the following weight proportion: 101: 26: 47: 25: 1. The spatial distribution and incorporation of Ce into the GAGG ceramic grains as well as the luminescence and scintillation performance are studied carrying out correlated experiments of photo-, radio- and cathodoluminescence including decay kinetics as well as energy dispersive X-ray spectroscopy combined with scanning electron microscopy. Optical absorption features were investigated using photothermal deflection spectroscopy. Cerium stays within the material mostly in the Ce3+ charge state. Its distribution in the bulk of the sample exhibits irregular trend indicating the tendency to coalesce in the middle.

The heat-treated oxyfluoride glasses with different contents of thulium Tm3+ and holmium Ho3+ ions have been studied using small-angle X-ray scattering and diffraction. With an increase in relative concentration of added Ho2O3 and Tm2O3 oxides, the growing in the average size of both nanoparticles and local density fluctuations in the glass matrix is observed. In addition, at high relative concentrations of initial rare-earth oxides, the appearance of a crystalline cubic phase PbF2:Tm-Ho is observed, which can provide a source of up-conversion luminescence in the studied glass materials. A change in the concentration of the initial Ho2O3 and Tm2O3 oxides does not effect on a morphology and fractal dimension of the formed luminescence nanoparticles. The structural aspects of nanoparticle formation with up-conversion luminescence phenomenon are discussed.

The glass‐ceramics (GC) of gadolinium aluminum gallium garnets with the expected composition of Gd 3 Al 3 Ga 2 O 12 :Ce and Gd 3 Al 3 Ga 2 O 12 :Ce,Be (GAGG:Ce and GAGG:Ce,Be, respectively) are fabricated by crystallization from the Gd 2 O 3 –Al 2 O 3 –Ga 2 O 3 –CeO 2 –SiO 2 –BeO (Gd:Ga:Al ratio is close to 3:2:3) glasses. The influence of Be 2+ co‐doping (including doping level) on the luminescent properties of the GAGG is demonstrated. In particular, Be co‐doping results in the suppression of the Ce 3+ ‐related radioluminescence (RL) and as a consequence, the light yield is lowered as well. The conclusion is made that Be 2+ creates effective electron or hole trapping centers.

Oxide ceramics with pyrochlore structure such as Laa(2)Zr(2)O(7) are promising materials for advanced multifunctional applications including extreme environment, such as space applications. They combine low thermal conductivity, suitable coefficient of thermal expansion to join supporting materials and have optical response in the UV-VIS region with up-converting and down-converting properties after doping, required for coating, sensors, and electro-optic applications. The effect of doping elements such as Er3+& nbsp;and Yb3+, replacing isomorphically lanthanum in the Laa(2)Zr(2)O(7) with pyrochlore cubic structure, on material photophysical properties was investigated by selective doping, in the molar ratio of Er3+/Yb3+ ranging from 0.5 to 5. The reflectance spectra of materials prepared by sol-gel co-precipitation method after sintering at 1400 ?, investigated in the UV-VIS-NIR range showed as expected well resolved absorptions due to the 4f-4f intra-configurational transitions. At the same time, dielectric properties of sintered samples were investigated by terahertz time domain spectroscopy. The refractive indices observed in the range of-4.46-5.15, indicate high dielectric permittivity at THz frequencies applicable in energy storage materials or THz communication components. For all samples a broad absorption band was found in the THz region and the band intensities were clearly associated with the doping amount of Er and Yb cations into the Laa(2)Zr(2)O(7) structure, at frequencies 0.75-1.02 THz. Significant correlation at the level of R-2 = 0.911 was found between the absorption band corresponding to the 4I15/2 & RARR; 2H11/2 transition at 520.5 nm and the integrated intensities of THz bands. Dielectric ceramic materials such as titanium-, tantalum and niobium-oxide based ceramics have permittivity in the range 20-30. The permittivity of studied Laa(2)Zr(2)O(7) was-20 and increased after doping by Er3+/Yb3+ to-21-26.

Glass ceramics in the form of MI2:Eu crystalline particles grown in MO-B2O3 glass (M = Ca, Sr, Ba) through recrystallization from the alloyed melt were fabricated. Eu2+ ions were detected in the CaI2 and SrI2 crystalline particles (not in the BaI2) inside the corresponding glasses. Some amount of Eu2+ centers are expected to originate from the MO-B2O3 glass hosts as well. This was confirmed by correlated electron paramagnetic resonance (EPR), photo- and radioluminescence (PL, RL) measurements. Peculiarities of the Eu2+ distribution and incorporation into the glass ceramics samples as well as charge and energy transfer properties are discussed in detail. Optimal conditions leading to the enhancement of the Eu2+ emission from the CaI2 and SrI2 crystallites inside the glasses were determined.

The oxyfluoride-lead-silicate-germanate glass with composition of 30SiO(2)-10GeO(2)-xPbO-(50-x) PbF2-10CdF(2)-yTm(2)O(3), x = 5, 25, 45, y = 0.01, 0.1, 0.5, 1.0 (mol. %) were prepared by melt-quenching technique and their spectroscopic properties, including parameters calculated by the JO method, were studied. A new approach for calculation of the pump efficiency of the F-3(4) level at excitation of the H-3(4) level by using stationary spectra of luminescence at transitions H-3(4)-> F-3(4) and F-3(4)-> H-3(6) was proposed. For the samples with a high content of Tm2O3, the efficiency reaches the value of 1.8. It was established that the quadrupole-quadrupole interaction between thulium ions dominates in the D-A energy transfer due to the cross-relaxation H-3(4)+H-3(6)-> F-3(4)+F-3(4). On the base of the rate equations, a new fitting procedure was proposed for obtaining the probabilities of donor acceptor, W-DA, and up-conversion, W-UP, energy transfer. It was obtained that W-DA similar to 6 10(5) 1/s and W-UP << W-DA for the samples with 0.5 and 1.0 mol. % of Tm2O3. The laser related properties, the stimulated emission cross sections, gain spectra, of the glass studied, were obtained and discussed.

The results of studies of the electrophysical and thermophysical characteristics of borosilicate glass designed to attenuate electromagnetic radiation in the microwave range are presented. The compositions of glass with the minimal tendency to crystallization are determined. The effect of the chemical composition of glass on its thermophysical (temperature coefficient of linear expansion (TCLE) and heat capacity) and electrophysical (attenuation index, standing wave ratio, and dielectric loss tangent) properties is found. The proposed glass compositions can be recommended for the manufacturing of products used as shielding against radiation.

A comprehensive study was performed of various types of aluminum-containing raw materials and their effect on glass formation during smelting of borosilicate glasses for type-E fiber. It is shown that on use of non-metallurgical alumina, as compared with metallurgical alumina, disthene-sillimanite concentrate, and kaolin, a savings of energy resources for glass formation processes from 2.64 to 16.30% obtains.

In this paper an original method for obtaining glass ceramic samples based on iodides of alkaline-earth elements activated by Eu2+ is proposed, their structural and spectral-luminescent properties are studied. The formation of glass ceramic samples containing both anhydrous iodides of alkaline-earth elements and crystalline hydrates of iodides of alkaline-earth element is confirmed by X-ray diffraction analysis when using in the synthesis process from 30 to 60 wt .% BaI2 : Eu2+, from 40 to 50 wt. % SrI2 : Eu2+ and 40 wt. % CaI2 : Eu2+. The possibility of adjusting the resulting color of glass ceramic samples emission (from blue to purple-red) by varying its composition is shown.

Present paper reports an approach to BaI2 :Eu2+ glass ceramic fabrication from a powder route. The structural, morphological, luminescent and paramagnetic properties of the materials synthesized this way have been investigated. X-ray diffraction analysis made evidence for the glass ceramics containing BaI2 center dot 2H(2)O and BaI2 inclusions when 50 wt.% of the starting iodide powder had been used in the synthesis process. According to scanning electron microscopy, only two samples demonstrated presence of ceramics particles inside: those with initial mix of 25 and 50 wt.% of the BaI2 :Eu2+. Photoluminescence spectra could be measured only in these samples. They were multicomponent as compared to the single band spectrum observed in the BaI2 :Eu2+ powder. Altogether this indicates europium distribution over several places with different environments in the materials. BaI2 dissolution in the glass matrix is confirmed further by electron paramagnetic resonance measurements. They have shown that the Eu2+ ions predominantly stay in the glass avoiding ceramic grains. Only negligibly small amount presumably occupies the ceramic part in the sample with the initial 50 wt.% part of the BaI2 powder. The Eu2+ -> Eu3+ charge transformation under 442 nm laser light irradiation has been observed in the glass ceramics as well. (C) 2020 SECV. Published by Elsevier Espana, S.L.U.

The results of obtaining hollow glass microspheres and their effect on the properties of water-dispersion facade coatings when the titanium oxide and calcium carbonate in the formula are replaced by an equivalent volumetric number of spheres are presented.

In this paper an original method for obtaining glass-ceramics based on barium iodide powder activated with Eu2+ is proposed, their structural and spectral-luminescent properties are investigated. X-ray diffraction analysis has evidenced that glass-ceramics containing BaI2 ∙ 2H2O and BaI2 are formed when 50 mas. % of the starting iodide powder is used in the synthesis process. The possibility of using glass-ceramics for preventing the contact of iodide powder with water vapor has been confirmed.

Glass ceramics based on Ce-doped garnets were fabricated by the controlled crystallization of CaO(MgO)–Y2O3–Al2O3–GeO2–SiO2–CeO2 glasses. Isomorphism of garnet-type crystallites and its influence on the crystall and luminescence properties was investigated.