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Phase equilibria in the BaB2O4–BaMoO4–BaF2 system are studied by the modified visual polythermal analysis, solid phase synthesis, differential scanning calorimetry, powder XRD, and chemical analysis. The liquidus of the system consists of the primary crystallization regions of BaB2O4, BaMoO4, and BaF2 separated by co-crystallization curves. A series of experiments on the growth of spontaneous α-BaB2O4, β-BaB2O4, BaMoO4, BaF2 crystals on a platinum loop and bulky BBO crystals are conducted. [ABSTRACT FROM AUTHOR]

Crystallization plays a critical role in realizing the functionalization of glass materials. However, it is imperative to understand the microscopic mechanism of both the formation and the phase transitions of nanocrystals during heat processes. Here, in the as-prepared SiO 2 -Al 2 O 3 -BaF 2 -Na 2 O glass, we studied the polymorphic phase transition of BaAl 2 Si 2 O 8 during heating-cooling circles, and a novel reversible transformation is found by serendipity. Using differential scanning calorimetry (DSC), we observed an endothermic event around 1047 K during heating at 20 K/min to 1173 K, and an exotherm event at 1024 K during the subsequent cooling. Based on the X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM), the reversible process was attributed to the transition between two morphs of BaAlF 5 nano-crystal. Na 2 O introduced in the studied glass system promotes the transformation between hexacelsian (Hexagonal) and celsian (Monoclinic). The results also show the formation of different types of crystals, such as, BaF 2 , Na 5 Al 3 F 14 and BaAlF 5 etc. [ABSTRACT FROM AUTHOR]

Glasses in the MnNbOF 5 –BaF 2 –FeF 3 system have been fabricated for the first time. The glass structure, thermal characteristics, and crystallization and magnetic properties have been investigated using IR and Raman spectroscopy, Differential scanning calorimetry (DSC), (XRD) X-ray powder diffraction and Superconducting Quantum Interference Device (SQUID) magnetometry. The NbO 2 F 4 and FeF n polyhedra form a glass network. During the devitrification of most of the glasses, the BaFeF 5 phase was found in the crystallization products. The possibility of obtaining crystalline phases in a glass matrix by heat treatment of glasses in the MnNbOF 5 –BaF 2 –FeF 3 system is demonstrated. [ABSTRACT FROM AUTHOR]

Oxyfluoride glass and glass‐ceramics are being studied due to the possibility of their utilization in many applications, such as thermoluminescent dosimeters, optical fibers, fluorescent concentrators, and temperature sensors. In order to improve the properties of glass, they are often crystallized. For this crystallization to be effective, knowledge and control of the structure of the starting material is required. Much work was done on silicate glass; however, a great interest exists in obtaining these kinds of materials in other matrices such as germanates, phosphates, and borates. Here, we present a structural study of some oxyfluoride borate glass with different concentrations of PbF2 by means of Nuclear Magnetic Resonance (NMR), Raman, and Fourier Transform Infrared (FTIR) spectroscopies. We also analyzed glass‐crystallization using Differential Scanning Calorimetry (DSC). The crystallization study was complemented with the use of Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED), for the purpose of identifying possible mechanisms of crystallization. Our results indicate, from the structural point of view, that the glass present groups with one or two BO4 species, such as diborate or pentaborate. The small variation in the BO4 fraction with the increase in PbF2 concentration would be an indication of the formation of F−BO3/2 species. Oxyfluoride borate glass containing BaO as a cation modifier and 30% PbF2 represents a good starting point for obtaining glass‐ceramics with a narrow size distribution of BaF2 nanocrystals. We also propose that the possible mechanism for oxyfluoride borate glass crystallization started with a separation of phases. [ABSTRACT FROM AUTHOR]

The thermodynamic properties of Ba-Pb alloys (activities, phase transitions, and partial molar quantities of Gibbs energy, entropy and enthalpy) were determined based on electromotive force (emf) measurements for thirteen mole fractions (xBa = 0.05-0.76) from 700-1060 K using an electrochemical cell: Ba(s) CaF2-BaF2 Ba(in Pb). The activity of Ba in liquid Pb was found to be as low as 2.0 × 10-10 at xBa = 0.05 and 973 K, reflecting a large excess partial molar Gibbs energy of -156 kJ mol-1 due to strong chemical interactions between Ba and Pb. Emf measurements were most reliable in the presence of a liquid phase, but were less reliable for high-melting compositions due to the formation of metastable phases during thermal cycling, confirmed by thermal and structural analyses using differential scanning calorimetry and X-ray diffraction. The experimentally-determined activity values of Ba-Pb alloys provide a new, reliable data set for further refinement in the assessment of thermodynamic properties for the Ba-Pb system. [ABSTRACT FROM AUTHOR]

• Achieved low hydroxyl absorption in fluorotellurite glass. • Effectively enhanced mid-infrared emission in heavily Er3+-doped samples. • The radiation properties of serial Er3+-doped samples are discussed and characterized. • The glass fiber has good fiber forming properties and anti-deliquescence ability. Heavily Er3+-doped TeO 2 –BaF 2 –La 2 O 3 –LaF 3 (TBLL) glasses with low hydroxyl absorption (α OH− ≈ 0.025 cm−1) and high glass transition temperatures (T g > 437 °C) were prepared. The Raman spectra and differential scanning calorimetry (DSC) curves were measured to characterize the structural and thermal properties of the glass samples. The emission properties of Er3+-doped TBLL glasses were studied under a 980 nm LD excitation, and the related transition mechanism was discussed. Intense fluorescence emission was noted at 1.55 μm and 2.71 μm, and the intensities of emissions increased monotonically as the Er 2 O 3 doping concentration increased from 0.5 to 6.0 mol%. The absorption and emission cross sections of Er3+-doped TBLL glass at 2.71 μm were estimated to be 7.90 × 10−21 and 8.47 × 10−21 cm2 using the Fuchtbauer–Ladenburg theory, respectively, which are much higher than those of many reported tellurite glasses. Furthermore, the undoped and 6.0 mol% Er 2 O 3 doped TBLL bare fibers were prepared. Their chemical durability was tested in deionized water, and the results indicated that the TBLL glass exhibited good antideliquescence ability. Finally, a broad emission band at ∼2720 nm was detected in the 6.0 mol% Er 2 O 3 doped TBLL bare fiber. These results demonstrate that the novel Er3+-doped TBLL fluorotellurite glass is a candidate for ∼3 μm fiber lasers. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of multicolor light-emitting nanomaterials based on rare earths (RE3+) are of great importance due to their possible use in optoelectronic devices, such as LEDs or displays. In the present work, oxyfluoride glass-ceramics containing BaF2 nanocrystals co-doped with Tb3+, Eu3+ ions were fabricated from amorphous xerogels at 350 °C. The analysis of the thermal behavior of fabricated xerogels was performed using TG/DSC measurements (thermogravimetry (TG), differential scanning calorimetry (DSC)). The crystallization of BaF2 phase at the nanoscale was confirmed by X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM), and the changes in silicate sol–gel host were determined by attenuated total reflectance infrared (ATR-IR) spectroscopy. The luminescent characterization of prepared sol–gel materials was carried out by excitation and emission spectra along with decay analysis from the 5D4 level of Tb3+. As a result, the visible light according to the electronic transitions of Tb3+ (5D4 → 7FJ (J = 6–3)) and Eu3+ (5D0 → 7FJ (J = 0–4)) was recorded. It was also observed that co-doping with Eu3+ caused the shortening in decay times of the 5D4 state from 1.11 ms to 0.88 ms (for xerogels) and from 6.56 ms to 4.06 ms (for glass-ceramics). Thus, based on lifetime values, the Tb3+/Eu3+ energy transfer (ET) efficiencies were estimated to be almost 21% for xerogels and 38% for nano-glass-ceramics. Therefore, such materials could be successfully predisposed for laser technologies, spectral converters, and three-dimensional displays. [ABSTRACT FROM AUTHOR]

• Glasses in ZrF 4 –BaF 2 –NaPO 3 system were prepared by melting 60ZrF 4 –40BaF 2 and NaPO 3 glasses. • Glass networks are constructed from fluorozirconate and phosphate subsystems. • Nucleation of crystalline phases begins at the 20 mol.% NaPO 3 content in the glass. • Fluorozirconate phases crystallize first and its can be centers of crystal formation. • Possibility of obtaining nanoceramics with nanocrystallites embedded in glass is shown. The glasses in the system of ZrF 4 -BaF 2 and NaPO 3 obtained by melting glasses of ZrF 4 -BaF 2 and NaPO 3 were studied by methods of IR and Raman spectroscopy, X-ray diffraction, SAXS and differential scanning calorimetry. An analysis of the data showed that the glasses are built of two sub-networks, in one of which crystallization centers are formed. It was shown possibility of obtaining mixed optical nanoceramics in which fluorozirconate nanocrystallites are embedded in a phosphate glass matrix. [ABSTRACT FROM AUTHOR]

Thermodynamic properties of Ba–Sn alloys were determined for Ba mole fractions (x Ba = 0.03–0.69) by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and electromotive force (emf) measurements. Six intermetallic compounds (BaSn 5 , BaSn 3 , Ba 3 Sn 5 , BaSn, Ba 5 Sn 3 , and Ba 2 Sn) were identified by XRD and the phase transition temperatures were determined by DSC up to x Ba = 0.50, which were used to delineate phase boundaries for constructing an experimentally-determined phase diagram. In addition, thermochemical solution properties were calculated by measuring emf values of Ba–Sn alloys using the following electrochemical cell: Ba(s) | CaF 2 –BaF 2 | Ba(in Sn) over 713–1063 K, including activity and partial molar quantities of Gibbs energy, entropy, and enthalpy. The activity of Ba in Sn was as low as 1.5 × 10−11 at x Ba = 0.03 and 923 K, indicating highly non-ideal solution behavior with a large excess partial molar Gibbs energy (−164 kJ mol−1). By integrating solution properties from emf measurements with the phase behavior by DSC and XRD, a reliable description of the Ba–Sn system was established. • Six intermetallics in Ba–Sn system were identified by XRD. • Experimental Ba–Sn phase diagram was constructed by XRD and DSC measurements. • Chemical potential of Ba in Sn was determined by emf measurements. [ABSTRACT FROM AUTHOR]

The ErF3-doped oxyfluoride phospho-tellurite glasses in the (40-x) TeO2-10P2O5-45 (BaF2-ZnF2) -5Na2O-xErF3 system (where x = 0.25, 0.50, 0.75, 1.00, and 1.25 mol%) have been prepared by the conventional melt-quenching method. The effect of erbium trifluoride addition on thermal, structure, and spectroscopic properties of oxyfluoride phospho-tellurite precursor glass was studied by differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR), and Raman spectroscopy as well as emission measurements, respectively. The DSC curves were used to investigate characteristic temperatures and thermal stability of the precursor glass doped with varying content of ErF3. FTIR and Raman spectra were introduced to characterize the evolution of structure and phonon energy of the glasses. It was found that the addition of ErF3 up to 1.25 mol% into the chemical composition of phospho-tellurite precursor glass enhanced 2.7 µm emission and upconversion. By controlled heat-treatment process of the host glass doped with the highest content of erbium trifluoride (1.25 mol%), transparent erbium-doped phospho-tellurite glass-ceramic (GC) was obtained. X-ray diffraction analysis confirmed the presence of BaF2 nanocrystals with the average 16 nm diameter in a glass matrix. Moreover, MIR, NIR, and UC emissions of the glass-ceramic were discussed in detail and compared to the spectroscopic properties of the glass doped with 1.25 mol% of ErF3 (the base glass). [ABSTRACT FROM AUTHOR]