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Solid electrolyte nanoceramics Pr SryF (y = 0.03, sp. gr. ) were obtained by high-energy milling of melt-grown crystals, followed by cold pressing. The phase composition, microstructure, morphology, and electrical properties of nanoceramics were studied using X-ray diffraction analysis, electron microscopy, and impedance spectroscopy. The room-temperature conductivity of the synthesized Pr0.97Sr0.03F2.97 nanoceramics (σcer = 1.7 × 10−7 S/cm) is much lower than the conductivity of the original single crystal (σcrys = 4.0 × 10−4 S/cm), which is due to its low (~75% of the theoretical value) density. Heat treatment of nanoceramics at 823 K in vacuum leads to a threefold increase in σcer, and annealing at 1273 K in a fluorinating atmosphere results in further increase in conductivity (σcer = 4.3 × 10−5 S/cm) due to the collective recrystallization and significant increase in the ceramics density (up to 90%). The mechanical milling and subsequent heat treatment of Pr SryF nanopowder make it possible to process single-phase highly conductive ceramics. The proposed method for the synthesis of ceramic fluoride nanomaterials as a technological form of solid electrolytes is a promising way for further developments in the field of creating fluorine-ion current sources and fluorine gas sensors. [ABSTRACT FROM AUTHOR]

LiRF4 (R = Y, Yb, Lu) nanoparticles (NPs), co-doped by Yb3+/Er3+ and Yb3+/Tm3+ ions, have been synthesized by high-temperature coprecipitation method. The influence of the molar ratio of precursors and the cation composition of matrices on the sizes and morphology of particles is investigated. The method of heterogeneous crystallization of these compounds using LiYF4 nanoseeds is optimized, which opens opportunities to controlled synthesis of LiRF4 NPs with required characteristics. Among the objects studied, LiYF4@LiYbF4:Tm3+@LiYF4 NPs demonstrate the most intense anti-Stokes photoluminescence in the UV (λ = 362 nm) and blue (λ = 450 nm) ranges, which exceeds the corresponding characteristics for β-NaYF4:Yb3+/Tm3+@NaYF4 particles. LiYF4@LiLuF4:Yb3+/Er3+@LiYF4 NPs are the most efficient IR converters in the (λ = 1530 nm) among the investigated isostructural matrices; their spectral-luminescence characteristics are close to those of the β-NaYF4:Yb3+/Er3+@NaYF4 compound with the equivalent degree of codoping. The results obtained give possibilities to consider LiYF4@LiYbF4:Tm3+@LiYF4 and LiYF4@LiLuF4:Yb3+/Er3+@LiYF4 NPs as a real alternative to the most widely used phosphors based on hexa-gonal β-NaYF4 host for photonics and biotechnology applications. [ABSTRACT FROM AUTHOR]

Hot pressing of a Si single crystal in the bulk of electrolytic Cr powder at 1213 K, with subsequent annealing in air, leads to the formation of an intermediate polycrystalline silicide layer at the interface between the initial components. The phase composition and microstructure of the transition layer and its vicinity were investigated by scanning electron microscopy, X-ray energy-dispersive microanalysis, and electron backscatter diffraction. The transition layer has a crystal structure of the hexagonal phase of chromium disilicide (sp. gr. P6222). An additional annealing up to 120 h leads to insignificant recrystallization of small grains into larger ones. [ABSTRACT FROM AUTHOR]