Congruently melting Ca 0.77 Sr 0.07 La 0.16 F 2.16 and Ca 0.70 Sr 0.11 Ce 0.19 F 2.19 fluorite solid solutions crystals in the CaF 2 –SrF 2 – R F 3 ( R = La, Ce) systems have been grown from melt by the Bridgman technique in a fluorinating atmosphere. Their optical, mechanical, electrophysical, and thermophysical characteristics have been studied. The crystals are transparent in a wide spectral range; their refractive indices are n D = 1.468 ( R = La) and 1.479 ( R = Ce), and their microhardness ( Н V ∼ 5.0 GPa) and ionic conductivity (σ ∼ 3 × 10 –3 S/cm at 823 K) exceed significantly the corresponding values for CaF 2 and SrF 2 crystals. The materials under study are promising isomorphic-capacious crystalline matrices for various applications in photonics and solid-state ionics.

A series of three-component isostructural fluorite crystals (Sr1–xBax)0.7La0.3F2.3 (sp. gr. \(Fm{\bar {3}}m\), 0 ≤ x ≤ 1), the compositions of which belong to the Sr0.7La0.3F2.3–Ba0.7La0.3F2.3 polythermal section in the SrF2–BaF2–LaF3 system, has been grown for the first time by vertical directional crystallization. Optical, mechanical, and electrical properties of three-component (Sr1–xBax)0.7La0.3F2.3 and two-component M0.7La0.3F2.3 (M = Sr or Ba) crystals have been investigated and subjected to comparative analysis. It is shown that all three-component crystals (Sr1–xBax)0.7La0.3F2.3 are promising optical design materials.

The dependences of the refractive indices of solid solutions based on cerium fluoride (Ce1−y Sr y F3 − y and Ce1 − y Ba y F3 − y ) on their composition have been studied. It is shown that at a light wavelength λ = 0.589 μm crystals of the Ce0.925Sr0.075F2.925 and Ce0.875Ba0.125F2.875 compositions have an average refractive index n av coinciding with the refractive index of polystyrene (n = 1.5975 ± 0.001) at this wavelength and can thus be used as fillers for cerium-containing composite scintillators based on polystyrene.

The refractive indices n of Sr1 − x R x F2 + 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 Sr0.9 R 0.1F2.1 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 − x R x F2 + 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.

The optical properties of the isoconcentration series of Cd0.9 R 0.1F2.1 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 Sr0.9 R 0.1F2.1 crystals. It is shown that the refractive indices in Cd1 − x R x F2 + x crystals, depending on the RF3 content, can be estimated using the method of molecular refraction additivity.

Crystals of the R 1 − y Sr y F3 − y phases (R = La, Ce, Pr, or Nd; 0 ≤ y ≤ 0.16) with tysonite (LaF3) structure are grown by the Bridgman method. A linear dependence of the crystal density on the SrF2 concentration has been revealed for each series of solid solutions. A scheme of heterovalent isomorphous substitution in the tysonite structure, R 3+ + F1− → M 2+ + V F, with compensation of the difference in the cation charges due to the formation of anion vacancies, is confirmed experimentally. The optical transmission spectra are measured in the wavelength range λ = 2.18–22.22 μm. It is shown that the 50%-transmission edge in the IR range is 10.5 μm for all crystals. The refractive index and the polarizability of crystals decrease with decreasing SrF2 content according to a linear law. The melting curves of the R 1 − y Sr y F3 − y phases studied have a maximum; therefore, these phases can be recommended for use as crystals with a high homogeneity and different optical properties in comparison with the corresponding RF3 crystals.

The results of the refraction study of two-component solid solution single crystals grown on the basis of rare-earth element (REE) fluorides with different content of strontium fluoride ( R1-xSrxF3-x, where R = La, Ce, Pr, Nd; 0 ≤ x ≤ 0,15) are presented. Experimentally obtained values of refractive indices and density have given the possibility to calculate some refraction characteristics of the crystals investigated: molar (Lorenz–Lorentz) refraction, polarizability, molar volume, and to analyze all the data obtained in two directions: with the increase of SrF2 content x for each binary system and according to the REE atomic number for one and the same x.

Congruently melting compositions in the series of solid solutions R 1 − x Sr x F 3 − x ( R = La-Nd with a defect structure of the tysonite type (LaF 3 ) were found by the comparing the densities (determined by hydrostatic weighing) of the top and bottom parts of the single crystals grown using the Bridgman method. Measurement errors are analyzed.

The presence of impurities in the crystals has an important influence on their properties. A sensitive method of the impurity control in the crystals without their destruction is the investigation of their absorption spectra. In this work we have studied the LaF3 tysonite crystals widely used as the laser matrices. The LaF3 crystals were grown from the melt by Bridgman-Stockbarger method using the reagents with trade mark "high pure" and "chemical pure". The crystal absorption spectra were recorded in the range of 200-300 nm and the obtained results have shown that the crystals grown from the "high pure" reagents had no absorption bands in the UV region and the crystals grown From the "chemical pure" reagents had well defined characteristic absorption bands at lambda = 205, 218, 235, 248 nm. Spectral experiments have confirmed the assumption that the UV-absorption bands in the latter crystal samples were caused by the presence of CeF3 impurity in the "chemical pure" reagents. A technique was developed for evaluation of CeF3 content in LaF3 crystals and in "chemical pure" mixture of LaF3 with the accuracy +/-0.0005 mol.%.

In this work the polarization absorption spectrum of homeotropically oriented comb-shaped liquid crystal polymer (LCP) film interposed in the electro-optical cell was investigated. The optical parameters of electrodes were estimated from the observed absorption spectra of the cell with and without polymer film using the method of interferometric extrema envelopes. This method enabled us to re-establish the true polarization absorption spectrum of the polymer. For this purpose the refractive index dispersion data of the substrates and the polymer obtained by independent investigation were used.

The present work is devoted to the order parameter S estimation in the comb-shaped liquid crystal polymer thin films. The polymer under study was placed in the electrooptical cell and its homeotropical orientation was realized by the action of electrical field between the electrodes. The polarization absorption spectra of the empty cell and the cell with polymer were investigated at different incidence angles of the light beam. The method of interferometric extremum envelopes was used for the processing of the quasiperiodical absorption spectra observed. This method gives the possibility to obtain the optical parameters of the cell electrodes and to re-establish the true polarization spectrum of the polymer film. The polymer order parameter S was calculated from the dichroic ratio for the polymer absorption band at revealed lambda = 405 nm. The refractive index dispersion data obtained for the substrates and the polymer from the independent measurements were used for this purpose. The effects of the local field on the order parameter value were also taken into account.

The temperature dependence of refractive indices of homeotropically oriented comb-shaped polymer films was determined with the help of optical interference wedge method. For order parameter S(T) estimation from the refractometrical data the information about the temperature dependence of the polymer density is needed and it is also necessary to choose a local field model. Born expression for the molecular refraction invariant in the large temperature range was used for evaluation of the polymer density temperature dependence. The problem of local field effects was investigated in detail on the example of the low-molecular LC PAA. It was shown that for the relative order parameter S(T) estimation it was possible to use Haller's extrapolation method. In this case the results obtained for different local field models are close to one another and to the results obtained by other independent methods.

Na0.4R0.6F2.2 single crystals with fluorite structure were grown by the Stockbarger method. Optical transmission spectra were recorded on the 2 mm thick samples of these crystals at room temperature in the broad spectral region (0.2 - 12 micrometer). It was found that the spectra of crystals with Dy, Ho, Er and Tm ions have the clearly defined discrete structure with a large number of absorption bands in visible, UV and nearest IR regions. The spectra become simpler on going from Dy to Yb. The spectra of crystals with Y and Lu are simplest, almost coinciding and similar to the NaF-crystal spectrum. The peculiarities of these spectra are due to the REE-ions presence in crystalline structure. All single crystals studied have the IR absorption edge at (lambda) approximately equals 12 micrometer. The spectra obtained are compared with these of other fluorides.