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The preparation of NaLnF 4 complexes, LnF 3 (Ln = La, Ce, Y) rare earth binary fluorides, CaF 2 and SrF 2 alkali earth fluorides, as well as mixtures of these compounds from their nitrates dissolved in molten NaNO 3 has been studied in order to select the ideal solvent for fluoride synthesis by spontaneous crystallization from flux. Sodium fluoride (NaF) was used as a fluorinating agent. The results of our experiments have confirmed that NaNO 3 melt is one of the most promising media for precipitating said inorganic fluoride materials within a broad temperature range (300-500 • C). Also, in contrast with precipitation/co-precipitation from aqueous solutions, our syntheses have resulted in obtaining equilibrium phases only.

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Using Fourier-transform infrared spectroscopy and optical ellipsometry, room temperature spectra of complex conductivity of single crystals of hexaborides GdxLa1−xB6, x(Gd)= 0, 0.01, 0.1, 0.78, 1 are determined in the frequency range 30-35000 cm −1 . In all compounds, in addition to the Drude free-carrier spectral component, a broad excitation is discovered with the unusually large dielectric contribution ∆ε=5000 -15000 and non-Lorentzian lineshape. It is suggested that the origin of the excitation is connected with the dynamic cooperative Jahn-Teller effect of B6 clusters. Analysis of the spectra together with the results of DC and Hall resistivity measurements shows that only 30-50% of the conduction band electrons are contributing to the free carrier conductivity with the rest being involved in the formation of an overdamped excitation, thus providing possible explanation of remarkably low work function of thermoemission of GdxLa1−xB6 and non-Fermi-liquid behavior in GdB6 crystals.

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Thin-film diamond−rare earth fluoride nanocomposites have been produced by chemical vapor deposition to be used as a source of intensive photo-and X-ray luminescence. The composites with embedded Eu-containing nanoparticles show highintensity orange narrow-band photoluminescence near the wavelength of 612 nm. Using β-NaGdF 4 :Eu instead of Eu(III) tri-(2,6pyridine dicarboxylic acid) and europium fluoride in the diamond matrix resulted in enhanced signal/noise ratio in the luminescence. The mapping of the spatial distribution of photoluminescence intensity on macro-and micro scale revealed highly uniform emission originated from the composite. The developed composite material with mechanically strong, highly thermally conducting and transparent diamond matrix opens a way to use the diamond− fluoride composites as photo-and X-ray luminescent screens (scintillators) capable to withstand high photon fluxes.