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This paper examines how the transformation of BaF from a single-crystalline to polycrystalline state as a result of uniaxial hot-forming influences its properties. With increasing strain, the microstructure of the material changes from a nonuniform polycrystalline one, with a block size of about 1 mm, to a classic ceramic structure made up of grains in which dislocations form walls, resulting in a subgrain structure. The best mechanical characteristics are offered by the ceramic produced at a strain on the order of 700%. The intensity of the fast X-ray luminescence component (band at 220 nm) is independent of strain, whereas that of the slow component (band at 310 nm) decreases with increasing strain. [ABSTRACT FROM AUTHOR]

Barium lanthanum fluoride powders have been prepared by reacting barium nitrate and lanthanum nitrate in molten sodium nitrate at 350 and 450°C, using a sodium fluoride as a fluorinating agent. A fivefold excess of sodium fluoride has been shown to prevent pyrohydrolysis. We have identified a phase of variable composition with the fluorite structure, Ba1–xLaxF2+x (0.3 < x < 0.5), which has high ionic conductivity (2.3 × 10–4 S/cm at 500 K) and an activation enthalpy for ionic transport of 0.50 ± 0.01 eV. [ABSTRACT FROM AUTHOR]

Single crystals of Ca1– хBaхF2 (x = 0.001–0.05 and 0.85–0.99) solid solutions have been grown by the Bridgman method, and their thermal conductivity has been measured in the range 50–300 K by an absolute steady-state axial heat flow technique. The thermal conductivity of all samples has been shown to decrease with increasing temperature. At 300 K, the lowest thermal conductivity of the samples with x ≤ 0.05 exceeds 6 W/(m K), and that of the samples with x ≥ 0.85 is a factor of 2 lower. [ABSTRACT FROM AUTHOR]

Lead telluride films have been grown on Si (100) and BaF2 (100) substrates by a modified hot-wall method using a graphite reaction chamber. According to X-ray diffraction, X-ray microanalysis, and scanning electron microscopy characterization results, the average growth rate of PbTe films having compositions within the homogeneity range of lead telluride increases with increasing lead vapor partial pressure and decreases with increasing tellurium vapor partial pressure, independent of the nature of the substrate. The rate of PbTe film growth has been shown to be maximal in the initial stage of the process and decrease monotonically over time, independent of the nature of the substrate. Independent of the growth time, the average growth rate of the PbTe films on the Si (100) substrates is considerably higher than that on the BaF2 (100) substrates. Reflection high-energy electron diffraction data indicate that the texture of the PbTe films on Si (100) corresponds to the substrate orientation and that the misorientation angle of the mosaic blocks does not exceed 20°. On the BaF2 (100) substrates, we observe epitaxial PbTe film growth with the orientation relationship (100), [011] PbTe ║ (100), [011] BaF2. [ABSTRACT FROM AUTHOR]

A ceramic 2-µm laser beam visualizer based on Ho-doped β-BaZrF is proposed. The ceramic has been prepared by crystallizing 60ZrF-35BaF-5BiF glass doped with 3 wt % HoF. Exciting the Ho I level by a Tm:LiYF (Tm:YLF) laser at λ = 1910 nm, we observed a strong red luminescence, due to the F → I transition, and a weaker, green luminescence, corresponding to the ( F, S) → I transition. The threshold power density of the Tm:YLF laser at which a red spot was observed on a ceramic sample was 1.1 W/cm. [ABSTRACT FROM AUTHOR]

We have prepared glasses and semicrystalline phases with a green color in the systems ZrF(53.5)-NaF(20)-BaF(20)-LaF(6.5 − x)-YbF( x) (0 ≤ x ≤ 6.5 mol %) (I) and ZrF(53.5)-NaF(20)-BaF(20 − x)-LaF(6.5)-YbF( x) (0 ≤ x ≤ 20 mol %) (II). Thermal analysis results demonstrate that, in both systems, the glass transition temperature of the samples containing ≤3 mol % YbF lies in the range 200-250°C, their heating curves show two or three crystallization events (at 320-340, 380-460, and 415-490°C), and their melting points range from 460 to 490°C. Increasing the YbF content of the glasses to 4 mol % and above (system I) has no effect on their glass transition temperature, reduces the temperature of the first crystallization event from 340 to 305°C, and produces extra peaks in the range 545-600°C, above the major melting peak, which can be accounted for by a nonequilibrium state of the glasses. Ytterbium difluoride substitution for barium difluoride (10 to 20 mol %) (system II) leads to the formation of semicrystalline phases and increases the glass-transition (305°C), crystallization (470-515°C), and melting (570-690°C) temperatures. The IR spectra of such samples show, in addition to a so-called 'featureless continuum' (∼500 cm), absorption bands characteristic of the Yb-F bond. Electronic spectra also confirm that the glasses contain both divalent and trivalent ytterbium. [ABSTRACT FROM AUTHOR]

The thermal expansion of the CaYF, CaYbF, CaCoF, BaLaF, and BaNdF solid solutions has been studied experimentally from below liquid-nitrogen temperature to room temperature. The results demonstrate that both the iso- and heterovalent dopants have a weak effect on the linear thermal expansion coefficient of the fluorite-structure crystals. [ABSTRACT FROM AUTHOR]