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This study looked at the thermal conductivity of translucent (Y1−xGdx)2O3 (where 0 ≤ x ≤ 1) solid solution ceramics in the temperature range from 50 K to 300 K. The samples were obtained by hot pressing from high-purity nanopowders at 1600 °C, no sintering additives were used. Compositions with cubic syngony (x ≤ 0.7) and a monoclinic one (x ≥ 0.9) were investigated. Furthermore, a dense sample of cubic Gd2O3 with a LiF sintering additive was obtained and its thermal conductivity was determined (k = 11.7 W/(m K) at 300 K). It was shown that in the range of solid solution ceramic compositions 0.2 ≤ x ≤ 0.7, the thermal conductivity was practically unchanged and close to the value k ≈ 5 W/(m K) at 300 K. [ABSTRACT FROM AUTHOR]

A variety of Er3+-, Tm3+-, and Yb3+-activated CaF2-, SrF2-, (Ca, Sr)F2- and (Sr, Ba)F2-based fluoride laser ceramics have been prepared by the hot-forming technique. Lasing of the SrF2:Yb3+, (Ca, Sr)F2:Er3+, (Ca, Sr)F2:Tm3+, (Ba, Sr)F2:Tm3+ and (Ba, Sr)F2:Yb3+ specimens with diode pumping has been observed for the first time. Thermal conductivity data for the above fluorite-type laser materials are also presented and discussed. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Bulk c-oriented CeF3 single crystals (sp. gr. P 3 ¯ c 1 ) were grown successfully by the vertical Bridgman technique in a fluorinating atmosphere. A description of the crystal growth procedure and the solution of the difficulties during the growth process are presented in detail. The anisotropy of the mechanical, thermal and electrophysical properties were studied for the first time. The maximum values of the thermal conductivity coefficient (α = 2.51 ± 0.12 W·m−1·K−1) and the ionic conductivity (σdc = 2.7 × 10−6 S/cm) at room temperature are observed in the [0001] direction for the CeF3 crystals. The Vickers (HV) and Berkovich (HB) microhardnesses for the (0001) , (10 1 ¯ 0) and (11 2 ¯ 0) crystallographic planes were investigated. The HB values were higher than the HV ones and decreased from 3.8 to 2.9 GPa with an increase in the load in the range of 0.5–0.98 N for the hardest (0001) plane. The { 11 2 ¯ 0 } , { 10 1 ¯ 0 } and { 0001 } cleavage planes were observed during the indentation process of the CeF3 crystals. The variability of Young's, the shear modules and Poisson's ratio were analyzed. A significant correlation between the shapes of the Vickers indentation patterns with Young's modulus anisotropy was found. The relationship between the anisotropy of the studied properties and the features of the CeF3 trigonal crystal structure is discussed. [ABSTRACT FROM AUTHOR]

Cubic KR3F10 (R = Y, Tb) single crystals have been successfully grown using the Bridgman technique. Growth of crystals of this type is complicated due to the hygroscopicity of potassium fluoride and melt overheating. The solution to the problem of oxygen-incorporated impurities has been demonstrated through the utilization of potassium hydrofluoride as a precursor. In this study, the crystal quality, structure features, and optical, thermal and electrophysical properties of KR3F10 were examined. Data on the temperature dependences of conductivity properties of KTb3F10 crystals were obtained for the first time. These crystals indicated thermal conductivity equal to 1.54 ± 0.05 Wm−1K−1 at room temperature caused by strong phonon scattering in the Tb-based crystal lattice. Ionic conductivities of KY3F10 and KTb3F10 single crystals were 4.9 × 10−8 and 1.2 × 10−10 S/cm at 500 K, respectively, and the observed difference was determined by the activation enthalpy of F− ion migration. Comparison of the physical properties of the grown KR3F10 crystals with the closest crystalline analog from the family of Na0.5−xR0.5+xF2+2x (R = Tb, Y) cubic solid solutions is reported. [ABSTRACT FROM AUTHOR]

ScF3 optical quality bulk crystals of the ReO3 structure type (space group P m 3 ¯ m , a = 4.01401(3) Å) have been grown from the melt by Bridgman technique, in fluorinating atmosphere for the first time. Aiming to substantially reduce vaporization losses during the growth process graphite crucibles were designed. The crystal quality, optical, mechanical, thermal and electrophysical properties were studied. Novel ScF3 crystals refer to the low-refractive-index (nD = 1.400(1)) optical materials with high transparency in the visible and IR spectral region up to 8.7 µm. The Vickers hardness of ScF3 (HV ~ 2.6 GPa) is substantially higher than that of CaF2 and LaF3 crystals. ScF3 crystals possess unique high thermal conductivity (k = 9.6 Wm−1К−1 at 300 K) and low ionic conductivity (σ = 4 × 10−8 Scm−1 at 673 К) cause to the structural defects in the fluorine sublattice. [ABSTRACT FROM AUTHOR]

The latest research on magneto-optical materials for Faraday devices has been repeatedly highlighting the benefits of using the crystalline media with the negative value of the optical anisotropy parameter (OAP). The reason is that these media have proven to be very efficient in eliminating the degrading impact of the thermal-stress-induced birefringence which occurs in the Faraday devices that are operated with high average power light. In this paper, we report on the successful growth of OAP-negative fluoride crystals – the KDy 3 F 10 (KDF) and Na 0.38 Dy 0.62 F 2.24 (NDF) – and on the characterization of the material properties allowing to assess the benefits of using these crystals for the Faraday devices. Unlike the recently commercialized OAP-negative KTb 3 F 10 (KTF) crystal, these crystals exhibit high transparency at the mid-IR wavelengths (> 1500 nm), for which there are currently no OAP-negative crystals available. And although the Verdet constant at these wavelengths is not exceptionally high (≤ 12 rad/Tm in the absolute value) it is sufficient for the practical implementation of a Faraday device based on these crystals using the currently available permanent magnets. In addition, the thermal conductivity of the KDF crystal is advantageously ∼ 24% higher than that of the state-of-the-art KTF crystal. • KDF and NDF crystals exhibit high transparency at the 1420–1550 and 1900–2350 nm. • The Verdet constant is ≤ 12 rad/Tm in the absolute value at these wavelengths. • The KDF crystal possesses ∼ 24% larger thermal conductivity than the commercialized KTF crystal. [ABSTRACT FROM AUTHOR]

The opportunity of growing of several centimeters in length LiGdF 4 single crystals by Bridgman–Stockbarger technique was demonstrated and the optically perfect LiGdF 4 single crystals with 8 mm and 55 mm in length were grown. The phase composition, thermal conductivity, basic optical and spectral-kinetic properties of LiGdF 4 single crystals were studied for the first time. For LiGdF 4 crystal, the resulting linear thermal expansion coefficients α is 11% larger, than for both LiYF 4 and LiYbF 4 crystals. The obtained thermal conductivity dependence k(T) is more pronounced compared to LiLuF 4 and LiYF 4. The absorption spectrum of the LiGdF 4 crystal shows absorption bands corresponding to the 8S 7/2 – (6D j , 6I j , and 6P j) transitions of Gd3+ ions. The measured room temperature lifetime of 6P j multiplet of Gd3+ ions was equal to 4.25 ± 0.05 ms. The values of the temperature gradient of the LiGdF 4 refractive index do not strongly depend on the wavelength. • Melt overheating during fluoride crystal growth with incongruent melting character allows increasing its transparent part. • The temperature-dependent XDR measurements showed that the lattice constants linearly increase with the temperature increased. • The dependence of refractive index on wavelength demonstrates the curve slope break at 500 nm. [ABSTRACT FROM AUTHOR]