Ion Transfer in CdF<Subscript>2</Subscript>-based Iso- and Polyvalent Solid Solutions

The ionic conductivity of solid solution Cd_0.77Sr_0.23F₂ is 1.6 × 10⁻⁴ S/cm at 500 K. The conduction mechanism changes from a vacancy mechanism to an interstitial one at 523–553 K. In solid solutions Cd_0.9R_0.1F_2.1 (R = La-Lu, Y), the activation enthalpy of conduction decreases from 0.9 to 0.8 eV with decreasing ionic radius of R³⁺, raising the 500-K conductivity from 6 ×10⁻⁶ S/cm for La³⁺to 6 × 10⁻⁵ S/cm for Lu³⁺. For crystalline Cd_0.95In_0.05F_2.05, ionic and electronic conductivities at 313 K equal 5 × 10⁻⁴ and 5 − 10⁻⁶ S/cm.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 627–632.Original Russian Text Copyright © 2005 by Sorokin, Buchinskaya, Sul’yanova, Sobolev.     

Ordering of tysonite structure in an as-grown Er0.715Ca0.285F2.715 crystal and in a component of annealed two-phase crystal of the Er0.67Ca0.33F2.67 composition

The structures of the as-grown tysonite phase (TP) Er_0.715Ca_0.285F_2.715 as grown and the tysonite component in a crystal of the Er0.67Ca0.33F2.67 composition annealed at 760°C have been determined by X-ray diffraction methods from the main reflections in the sp. gr. P6₃/mmc, Z = 2. Ca²⁺ cations in the Er_0.715Ca_0.285F_2.715 structure occupy the 2c site on the 6₃ axis, thus confirming the conclusion about the symmetrizing effect of alkaline earth cation, which was made previously for the Y_0.715Ca_0.285F_2.715 compound. Er³⁺ cations are disordered over 6h sites around this axis. The Er_0.67Ca_0.33F_2.67 composition contains Er_0.67+δCa_0.33?δF_2.67+δ TP and inclusions of distorted fluorite phase rhβ-Ca₈Er₅F₃₁. The tysonite and two fluorite lattices have no “correct” relationship. Ca²⁺ cations and a half of TP Er³⁺ cations are fixed in the 2c sites, while the other Er³⁺ cations are disordered over the 6h sites. Superstructural ordering occurs in Er_0.715Ca_0.285F_2.715 crystals; however, the process is not completed, as follows from the character of the diffraction pattern. Weak satellite reflections in the diffraction pattern of the Er_0.67Ca_0.33F_2.67 composition are indicative of the development of TP ordering processes but remain unfit for structural calculations.     

Ionic Conductivity of Pb0.67Cd0.33F2 Ceramics Obtained by Mechanical Synthesis and by Grinding of a Crystalline Solid Solution

Crystallography Reports - Ceramic samples of the Pb0.67Cd0.33F2 composition have been obtained using grinding and mechanical synthesis with subsequent cold pressing. The ceramic density was 84...     

Properties of CdF2:Ga as a medium for real-time holography

The metastable nature of the excited state of bistable Ga centers in semiconducting CdF₂ crystals allows for the use of CdF₂:Ga and CdF₂:Ga,Y crystals as materials for real-time holography over a wide range of response times (1–1000 ms). The characteristics of these materials and optimal conditions for their use are discussed in the framework of a model that describes the decay of photo-induced gratings written in them. Received: 20 November 2000 / Published online: 20 April 2001     

A new optical medium—Cd<Subscript>0.75</Subscript>Sr<Subscript>0.25</Subscript>F<Subscript>2</Subscript> single crystals

For the first time, single crystals of the Cd_0.75Sr_0.25F₂ solid solution with the fluorite structure are grown from melt by the Bridgman-Stockbarger method. The composition of these single crystals corresponds to the composition congruently melting at the minimum point on the phase diagram. The maximum diameter of the crystal is 50 mm; the maximum height is 30 mm. The vickers microhardness of the semitransparent crystals equals 191 ± 43 kg/mm². The transmission cutoff in the IR range is ～10 μm.     

Ionic conductivity of multicomponent fluorite-structured fluorides

Influence of mixing of homovalent cations on the fast anionic conductivity, static permittivity, and thermal diffusivity is investigated in multicomponent fluorite-structured concentrated solid solutions of alkali earth and rare earth fluorides. Influence of mixing of alkali earth cations on electrical properties of fluoride superionics is studied in Ba_{0.7 − x} Sr _x La_0.3F_2.3 single crystals and Ca_{0.85 − x} Sr _x Nd_0.15F_2.15 transparent polycrystals. Influence of mixing of rare earth cations on electrical properties of fluoride superionics is studied in Ba_0.75La_{0.25 − x} Nd _x F_2.25 and Ba_0.35Sr_0.35(R ₁, ..., R _i )_0.3F_2.3 (i = 1–6; R _i stands for rare earth elements) single crystals. It is shown that the ionic conductivity decreases with increasing difference between mean ionic radii of rare earth and alkali earth cations. Up to 350°C, the fastest ionic conductivity is found in Ba_0.35Sr_0.35La_0.3F_2.3 single crystals.     

Pentagonal two-loop ring interferometer

Results of work on the assembly and adjustment of an original pentagonal, two-loop interferometer are reported; the interferometer is a passive version of a compact laser gravitational wave detector. It is shown that the correlative automatic noise-compensation system developed for the project is capable of lowering the phase noise level in the resultant signal channel of the detector by two orders of magnitude. Zh. Tekh. Fiz. 68, 121–125 (May 1998)     

Growth and defect structure of CdF2 crystal and nonstoichiometric Cd1−x R x F2+x phases (R are rare earth elements and in): 6. Growth and ionic conductivity of Cd0.904In0.096F2.096 single crystal

Cd_0.904In_0.096F_2.096 crystals with fluorite-type defect structures have been grown from melt in a fluorinating atmosphere by the Bridgman method, and their ionic conductivity is investigated. The fluorine-ion transport activation enthalpy in Cd_0.904In_0.096F_2.096 (ΔH = 0.68 eV) is much smaller than the corresponding characteristic of the crystals belonging to the isoconcentration series Cd_0.9 R _0.1F_2.1, R = La-Lu, Y (ΔH = 0.8–0.9 eV). The ionic conductivity of Cd_0.904In_0.096F_2.096 is σ = 2 × 10^?4 S/cm (at 467 K); this value exceeds the conductivity of the CdF₂ crystal matrix and the highest conductivity Cd_0.9 R _0.1F_2.1 crystals with rare earth elements by factors of 3 × 10³ and ～10, respectively. Nonstoichiometric crystals of solid electrolyte Cd_{1 ? x} In _x F_{2 + x} have the highest conductivity out of all studied electrolytes based on the CdF₂ matrix.     

Mechanosynthesis of Fluorite Solid Solution in the PbF2–CdF2 System

Crystallography Reports - Pb0.67Cd0.33F2 solid solution with a fluorite-type structure has been synthesized for the first time using high-energy grinding of the initial components, PbF2 and CdF2,...     

The growth and defect structure of CdF2 and nonstoichiometric Cd1 ? xRxF2 + x phases (R are rare earth elements or in): Part VI. The optical properties of Cd0.9R0.1F2.1 crystals

The optical properties of the isoconcentration series of Cd_0.9 R _0.1F_2.1 crystals (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu) grown from a melt by the Bridgman method have been investigated. The crystals have an anomalous birefringence (∼10⁻⁶) nonuniformly distributed over the sample diameter; the dichroism in them does not exceed 10⁻⁹. Scanning using a spectral modulator showed the nonuniform distribution of rare earth elements over the crystal diameter. The refractive indices n have been measured at wave-lengths of 0.436, 0.546, and 0.589 μm. The character of change in n along the rare-earth series is nonuniform and similar to the change in n in Sr_0.9 R _0.1F_2.1 crystals. It is shown that the refractive indices in Cd_{1 − x} R _x F_{2 + x} crystals, depending on the RF₃ content, can be estimated using the method of molecular refraction additivity. Original Russian Text ? A.F. Konstantinova, T.M. Glushkova, I.I. Buchinskaya, E.A. Krivandina, B.P. Sobolev, 2009, published in Kristallografiya, 2009, Vol. 54, No. 4, pp. 648–651.