D. N. Karimov

Growth of congruently melting Ca0.59Sr0.41F2 crystals and study of their properties

AbstractHomogeneous crystals of Ca0.59Sr0.41F2 alloy (sp. gr., Fm

Nanostructured crystals of fluorite phases Sr1 − xRxF2 + x (R are rare earth elements) and their ordering: 5. A study of the ionic conductivity of as-grown Sr1 − xRxF2 + x crystals

\bar 3

Investigation of multicomponent fluoride optical materials in the UV spectral region: I. Single crystals of Ca1−xRxF2+x (R = Sc, Y, La, Yb, Lu) solid solutions

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 nD = 1.436, microhardness Hμ = 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.

Growth and magneto-optical properties of Na0.37Tb0.63F2.26 cubic single crystal

The refractive indices n of Sr1 − xRxF2 + x crystals (R = Y, La-Lu; 0 ≤ x ≤ 0.5) have been measured at wavelengths of 0.436, 0.546, and 0.589 μm. It is established that n increases when there is an increase in the RF3 content x according to a weakly quadratic law for each R. For the isoconcentration series of Sr0.9R0.1F2.1 crystals, the change in n in the series of rare earth elements has a pronounced nonlinear character, which reflects the nonmonotonous change in the properties of compounds in the R series. It is shown that the method of molecular refraction additivity can be used to calculate n for Sr1 − xRxF2 + x crystals. By varying the RF3 content in them, one can obtain optical media with a gradually varied refractive index n in the range 1.44–1.55, thus filling the gap in the n values between high ones for RF3 crystals and low ones for crystals of alkaline earth fluorides MF2.

Thermophysical characteristics of Ca1−xSrxF2 solid-solution Crystals (0 ≤ x ≤ 1)

The ionic conductivity σ of Sr1 − xRxF2 + x crystals (R = Y, La-Lu) has been measured in the temperature range of 324–933 K. The isomorphic introduction of R3+ ions into SrF2 is accompanied by an increase in conductivity up to four orders of magnitude, which makes these crystals superionic conductors. It is shown that the conduction mechanism in Sr1 − xRxF2 + x crystals changes when passing from R = La-Nd to R = Sm-Lu. A change in the type of cluster of structural defects between Nd and Sm is suggested. The concentration dependences of σ and the activation energy of charge-carrier migration (Ea) for Sr1 − xRxF2 + x are nonlinear. For crystals with R = La or Nd, these dependences are interpreted within the percolation model of “defect regions,” the minimum size of which is estimated to be ∼700 Å3. It is shown that the electrical properties of the crystals can be controlled by varying the RF3 type and concentration. The Sr1 − xRxF2 + x crystals (R = La-Nd, 0.3 ≤ x ≤ 0.5), for which σ = (2−3) × 10−2 S/cm at 673 K and Ea = 0.6−0.7 eV, have the best electrolytic characteristics.

Calculation of the Refractive Indices of M1-xRxF2+x Crystals (M = Ca, Sr, Ba, Cd, Pb; R are Rare Earth Elements)

Transmission spectra of two-component crystals of Sr1−xRxF2+x (R = Y, La-Lu; 0 ≤ x ≤ 0.5) in the 1–17-μm wavelength range were studied. The spectral characteristics of these crystals and of single-component crystals of MF2 (M = Ca, Sr, or Ba) and RF3 (R = La-Nd) were compared. The transmission cutoff of Sr1−xRxF2+x crystals is shifted to shorter wavelengths with increasing x. The same tendency is observed with the increasing atomic number R of rare-earth elements for two isoconcentration series of Sr1−xRxF2+x (x ∼ 0.10 and 0.28). This tendency is pronounced at large x. The transmission cutoff of Sr1−xRxF2+x crystals can be varied in the range of from 10.7 to 12.2 μm by changing their qualitative (R) and quantitative (x) composition. Hence, these crystals can be assigned to multicomponent fluoride optical materials with controlled optical characteristics. The Sr1−xRxF2+x crystals, where R = Ce-Sm, were shown to be promising materials for the design of selective optical filters in the 2–10-μm spectral range.

Single crystals of the fluorite nonstoichiometric phase Eu0.9162+Eu0.0843+F2.084 (conductivity, transmission, and hardness)

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 Ca1−xRxF2+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.

Ionic conductivity of congruently melting Ca0.6Sr0.4F2 and Ca1 − x − ySryRxF2 + x (R = La, Ce, Pr, Nd) single crystals with fluorite structure

Crystals of Na0.37Tb0.63F2.26 solid solution with a fluorite structure have been grown from melt by the Bridgman technique. The measured values of the Verdet constant are V = 0.35 ± 0.02 and 0.105 ± 0.01 arcmin/(Oe cm) for λ = 633 and 1060 nm, respectively. The dispersion of the Verdet constant is studied in the range of 380–1060 nm. The Na0.37Tb0.63F2.26 crystal is somewhat inferior to the previously studied noncubic fluoride crystals containing Tb3+ ions yields by V(λ) and is close to KTb3F10 crystal in totality of properties.