The luminescence, reflection, and luminescence excitation spectra of two-component Ca1 − x Sr x F2:Ce3+ (0.05 mol %) (x = 0.14, 0.25, 0.4, 0.6, and 0.75) have been studied at room temperature and T = 8 K. It is shown that the luminescence bands (upon 130-eV photon excitation) in the range of 200 to 400 nm are attributed to singlet and triplet self-trapped exciton luminescence and to 5d-4f transitions in Ce3+.

Results of studying the properties of luminescence spectra of wide-band fluoride CaF2, Ca0.9Y0.1F2.1, Na0.4Y0.6F2.2, Na0.4Yb0.6F2.2, and BaYb2F8 crystals (pure and doped with Ce3+ and Yb3+ ions) under synchrotron radiation excitation with energies ranging from 3 to 60 keV are presented. Luminescence spectra are obtained in the region 200–600 nm. Transmission spectra are studied, and the effect of intense short-wavelength radiation on the optical properties of these crystals is studied.

LiYbF4 single crystals, nominally pure and doped with Ce3+ ions, of optical quality and up to 60 mm in diameter, have been grown by vertical directed crystallization. The optical and mechanical properties of the crystals have been studied. The refractive index dispersion for LiYbF4 in the range of 0.4-0.6 mu m can be described by the dependence n (2)(lambda) - 1 = A lambda(2)/(lambda(2) - lambda (0) (2) ), where A = 1.14 and 1.21 and lambda(0) = 0.074 and 0.080 mu m for n (o) and n (e), respectively. The sample microhardness exceeds 2.6 GPa. LiYbF4 crystals are transparent in the range of 0.17-9 mu m and have an absorption band in the range of 0.9-1.2 mu m. It is shown that LiYbF4 crystals doped with Ce3+ ions can be used as optical cut-off UV filters in the operating range lambda = 0.25-0.28 mu m.

Homogeneous crystals of Ca0.59Sr0.41F2 alloy (sp. gr., Fm \(\bar 3\) m, a = 0.56057 nm), corresponding to the point of minimum in the melting curve in the CaF2-SrF2 phase diagram, have been grown by the vertical Bridgman method. The optical, mechanical, electrical, and thermophysical properties of Ca0.59Sr0.41F2 and MF2 crystals (M = Ca, Sr) have been studied and comparatively analyzed. Ca0.59Sr0.41F2 crystals are transparent in the range of 0.133–11.5 μm, have refractive index n D = 1.436, microhardness H μ = 2.63 ± 0.10 GPa, ion conductivity σ = 5 × 10−5 S/cm at 825 K, and thermal conductivity k = 4.0 W m−1 K−1 at 300 K. It is shown that the optical properties of Ca0.59Sr0.41F2 crystals are intermediate between those of CaF2 and SrF2, whereas their mechanical and electrical characteristics are better than the latter compounds.

LiYbF4 single crystals, nominally pure and doped with Ce3+ ions, of optical quality and up to 60 mm in diameter, have been grown by vertical directed crystallization. The optical and mechanical properties of the crystals have been studied. The refractive index dispersion for LiYbF4 in the range of 0.4–0.6 μm can be described by the dependence n 2(λ) − 1 = Aλ2/(λ2 − λ 0 2 ), where A = 1.14 and 1.21 and λ0 = 0.074 and 0.080 μm for n o and n e, respectively. The sample microhardness exceeds 2.6 GPa. LiYbF4 crystals are transparent in the range of 0.17–9 μm and have an absorption band in the range of 0.9–1.2 μm. It is shown that LiYbF4 crystals doped with Ce3+ ions can be used as optical cut-off UV filters in the operating range λ = 0.25−0.28 μm.

The spectral properties of two-component Ca1-xSrxF2:Ce3+(0.05 mol%) (x = 0.75, 0.41, 0.25, 0.14) crystals in UV spectral region were investigated. It was shown that spectral properties of Ca1-xSrxF2:Ce3+(0.05 mol%) in UV spectral region have intermediate position between those for pure CaF2 and SrF2 crystals. The optical constants were calculated from reflectance spectrum for CaF2, SrF2, Ca1-xSrxF2:Ce3+(0.05 mol%) (x = 0.75, 0.25) crystals by use of Kramers-Kronig relations for complex reflection coefficient and Fresnel formulas.

Crystalline materials that are transparent in the vacuum UV spectral region and currently used have been reviewed. Transmission of crystals of solid solutions with the fluorite structure Ca 1− x R x F 2+ x ( R = Sc, Y, La, Yb, Lu) in the UV and vacuum UV spectral regions has been investigated. It is shown that application of different methods of purification of fluorides from some impurities can significantly improve the optical quality of fluoride multicomponent crystals in the short-wavelength spectral region.

The short-wavelength transmission spectra of Na 0.4 R 0.6 F 2.2 crystals with R = Y, Yb, or Lu have been investigated. For these crystals, the VUV transmission cutoffs are 78750, 58820, and 75200 cm −1 , respectively. The 4 f n –4 f n −1 5 d absorption and excitation spectra of Na 0.4 Y 0.6 F 2.2 crystals activated with Ce 3+ , Pr 3+ , Nd 3+ , Er 3+ , Tm 3+ , and Yb 3+ ions have been analyzed in the range 30000–80000 cm −1 . The energy positions of the lowest levels of the 4 f n −1 5 d configurations of these ions in the fluorite crystal matrix Na 0.4 Y 0.6 F 2.2 are determined. The absorption band in the spectral range 60600–70000 cm −1 in Na 0.4 (Y, Yb) 0.6 F 2.2 crystals is due to the charge transfer from F − to Yb 3+ . It is shown that the environmental symmetry of Ce 3+ ions in Na 0.4 R 0.6 F 2.2 ( R = Y, Yb, Lu) crystals is almost identical.