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For the first time catalytic systems based on HZSM-5 zeolites (Si/Al=12, 25, 40) with nanosized anatase (NA) were obtained in situ by a modified hydrothermal method and a sol-gel method. Initial HZSM-5 and NA/HZSM-5 were characterized (XRPD, XAS, FT-IR, DSC, BET, XPS, SEM, TPD) and analyzed in the reactions of propane (liquefied petroleum gas) conversion (РС; temperature range 200–870 °С) with the formation of the main products propylene (C3H6, PP) and ethylene (C2H4, ETH) and liquid ethanol conversion (EC; temperature range 150–360 °C) with the formation of diethyl ether ((C2H5)2O, DEE) and ETH. In the PC reaction the maximum selectivity (SETH = 75%) and conversion (αP = 65%) were obtained on HZSM-5(40) (650 °С). With an increase in the NA content in NA/HZSM-5 SETH value increases up to 85%. In the EC reaction SDEE/ETH~98–99% was reached on HZSM-5(25) (200 °C) and HZSM-5(40) (300 °C); the αE to ETH is comparable (94%) for all HZSM-5 (300 °C). Modification of HZSM-5 with NA leads to a shift in the EC reaction temperature to lower temperature region (αE to ETH ~98% at 280 °C) with SDEE/ETH~94–100% for NA/HZSM-5(25) and NA/HZSM-5(12) obtained by a modified hydrothermal method. It was established the relationship between HZSM-5 and NA/HZSM-5 catalytic activity and their characteristics: Si/Al, NA content and Ti coordination number (NA/HZSM-5), the content of "zeolite water" with OH groups, specific surface area, meso- and micropores volume and spherical particles size (HZSM-5), surface energy of adsorption centers (HZSM-5 and NA/HZSM-5), and hence the content of acid sites, the strength of which is also determined by the temperature of the catalytic reaction. The reaction mechanisms have been presented. The obtained NA/HZSM-5 catalysts have a higher or comparable catalytic activity to commercial ones, but low cost, ease of preparation, and versatility.

Composite nanoparticles with a core consisting of associated anatase crystallites and a polymeric shell consisting of poly(N-vinylpyrrolidone) or poly(N-vinylcaprolactam) were synthesized and found to have antimicrobial activity against Escherichia coli and Staphylococcus aureus as well as photocatalytic activity in decomposition of methyl orange and methylene blue dyes. The highest antibacterial activity of the particles with poly(N-vinylpyrrolidone) shell is due to the larger amount of S O 4 2 − groups and water adsorbed on the surface, while their photocatalytic activity is comparable with that of commercial nanoanatase samples.

Promising luminescent CsCdX3 (X = Cl, Br) single crystals, both nominally-pure and doped with bismuth, have been studied comprehensively by X-ray diffraction, X-ray synchrotron radiation, and X-ray absorption spectroscopy. Crystal structure refinement shows vacancies in the Cs crystallographic site and partial substitution of Cd2+ ions by Bi3+ ones in both CsCdCl3 and CsCdBr3 (point defects BiCd•), which is consistent with the results of X-ray absorption spectroscopy. The assumed presence of Bi1+ ions in the Cs1+ sites of doped CsCdX3 (X = Cl, Br) crystals is not confirmed. In the photoluminescence spectra of Bi-doped CsCdCl3 and CsCdBr3 crystals, a single band in the near-IR spectral range with a maximum around 1000 nm is caused by point defects BiCd•. Photoluminescence spectra and decay kinetics of Bi-doped CsCdX3 (X = Cl, Br) indicate their promising use as luminescent materials.

Single-crystal sillenite-type Bi24(M2-xMn4+x)O40 (M = Al3+, Fe3+, Ge4+, Ti4+, Cr4+, V5+) solid solutions have been studied by a complex of methods: single crystal and powder X-ray diffraction; EXAFS/XANES, IR and Raman spectroscopies; scanning and transmission electron microscopies; electron probe X-ray microanalysis. Structures of Bi24(M2-xMnx)O40 (M = Al, Fe, V, Ge) solid solutions contain Mn ions with two formal charges, Mn4+ and Mn5+, as well as vacancies in the Bi (M = V) and O (M = Cr, Fe, Al, V) sites. For the Bi24(M2-xMnx)O40 (M = Fe, Cr, V), a partial occurrence of Bi atoms in the tetrahedral sites has been detected by X-ray diffraction, which was confirmed by IR and Raman spectroscopies. Two isostructural sillenite-type solid solutions based on the Bi24Mn2O40 and γ-Bi2O3 with the impurity phases Mn2O3 and Bi2Mn4O10 were found in the system with M = Cr. Limits for isomorphic substitutions in the Bi24(M2-xMnx)O40 (M = Al, Fe, Ge, Ti, Cr, V) systems were theoretically estimated and compared with the experimental results obtained. A potential of elaborated combination of methods aimed at determining the precise real composition of solid solutions not identical to that of the initial charge was demonstrated. Homogeneity regions for sillenite family phases were predicted.

Czochralski-grown colorless and pink Bi4Ge3O12 (BGO) single crystals have been characterized by the X-ray diffraction, X-ray absorption, and luminescence and optical spectroscopy. Additional high-temperature vacuum annealing of the as-grown colorless crystal at 900–950 °C using a special reducing agent leds to the appearance of pink coloration and modification of its properties. The refinement of actual compositions of both BGO crystals showed the distribution of the Bi3+ions over two, tetrahedral and octahedral, sites, the Bi content in the colorless crystal being greater and lower in the octahedral and tetrahedral sites, respectively, compared with the colored crystal. A small amount of Bi5+ions was revealed in the tetrahedral sites of the colorless crystal. Oxygen vacancies, as a part of the color center responsible for the crystal coloration, were found in the structure of pink sample. The pink BGO crystal is characterized by photoluminescence in the near infra-red spectral range.

The nonlinear optical (NLO) properties of native defect-rich ZnO single crystals were studied in details within the excitation of the continuous wave (CW) and pulsed laser radiation at 532 nm (2.33 eV). Analysis of the experimental data of optical elastic scattering, Fourier transform infrared (FTIR), near infrared–visible–ultraviolet (NIR–Vis–UV) spectra recorded in reflection and absorption modes, and data of photoluminescence (PL) spectroscopy confirmed the contribution of both intrinsic defects and their clusters, being determined before by neutron diffraction and XRD analysis. It was shown that the high sensitivity of the NLO diagnostics via self-action of a laser beam is due to the resonant excitation of the deep defects states at wavelength 532 nm. It was also demonstrated the correlation of the real and imaginary parts of the cubic NLO susceptibility with PL and FTIR spectroscopies data dealing with the defect bands manifestation, while the elastic optical scattering and Vis-NIR spectroscopy data – with the intrinsic defect content. High photoinduced polarizabilities of the excited states provide application of the refractive NLO response and the optical elastic scattering indicatrices analysis as an express nondestructive technique to reveal the deep defects content in the bulk ZnO.

This article presents the results of a study of three commercial titanosilicalites (TS-1, TS-1N, TS-1G) with general formula [(TixSi12-x)O24] × wH2O (MFI-type) using the X-ray study (XRPD), IR spectroscopy (FT-IR), X-ray absorption spectroscopy (EXAFS/XANES), differential scanning calorimetry (DSC), Brunauer–Emmett–Teller method (BET), UV-VIS spectroscopy. It was established that the samples contain amorphous oxygenous titanium-containing formations, which does not allow the use of quantitative elemental methods of analysis to determine the content of titanium ions in the framework. The full-profile Rietveld method was used to determine the silicate modules (Si/Ti = 53 for TS-1, Si/Ti~47 for TS-1N and TS-1G) and the coordination numbers of titanium: CNTi~5.0, CNTi = 4.5, CNTi>5.0, respectively in the structures of TS-1, TS-1N, TS-1G. The distribution of Ti4+ ions over the sites of the MFI-type structure with the orthorhombic symmetry (space group Pnma, z = 8) were found: T2, T6, T10 for TS-1, T8, T10, T5 (unlikely) for TS-1N (Т10 double positions in sinusoidal channels) and Т2, Т10, Т12, Т9 (unlikely) for TS-1G (Т10 and Т12 double positions in sinusoidal channels). The best indicators of the allyl chloride epoxidation in the epichlorohydrin process at 30 °C were achieved for TS-1N and TS-1G. A higher yield of acetaldehyde was found on the TS-1(75) sample (TS-1 sample annealed at 75 °C for 2 h) at 290 °C (non-oxidative ethanol conversion), and ethylene - on the TS-1G(500) sample (TS-1G annealed at 500 °C for 2 h) at 700 °C (propane conversion). The revealed correlations between the catalytic parameters and the characteristics of the samples studied were discussed.

A structural features, real compositions, and point defects of nominally pure and Cr- and Ni-doped Sr 0.61 Ba 0.39 Nb 2 O 6 (SBN) crystals, which structure contains four chemically-different and ten crystallochemically-different atoms, have been determined using neutron, X-ray single crystal, X-ray powder, and X-ray synchrotron diffraction techniques, and EXAFS/XANES spectroscopy. The location of transition metal ions has been identified based on the analysis of electron (nuclear) density and confirmed by the EXAFS/XANES together with the definition of formal charges of Ni atoms in Ni-doped SBN crystals. The scope and application possibilities of diffraction methods and EXAFS/XANES spectroscopy for the determination of structural features and defect formation in functional bulk nominally-pure and Cr- and Ni-doped Sr 0.61 Ba 0.39 Nb 2 O 6 single crystals is established.

Single-crystal (Bi,Sm) 24 V 2 O 40 solid solutions with sillenite structure, grown by the hydrothermal method for the first time, have been studied using single-crystal X-ray diffraction, synchrotron radiation, and infrared spectroscopy. The real composition has been refined. The presence of Sm 3+ and Bi 3+ ions in one crystallographic site was determined by single-crystal X-ray diffraction and confirmed by the analysis of infrared spectra and calculation of the degree of distortion of the real [BiO 5 ] polyhedron.

Single crystals of scandium-containing rare-earth garnets in system R-Sc-C-O (R3+=Y, Gd; C3+=Al, Ga) have been grown by the Czochralski technique. X-ray diffraction analysis has been used to refine crystal compositions. The fundamental difference between the melt compositions and compositions of grown crystals has been found (except for compositions of congruent-melting compounds, CMC). The specific features of garnet solid solution formation have been established and the ternary diagrams with real or hypothetical phases have been built. The dinamics of coordination polyhedra changes with the formation of substitutional solid solutions have been proposed based on the mathematical modeling and experimental data. Possible existence of CMC with garnet structure in different systems as well as limit content of Sc ions in dodecahedral and octahedral sites prior to their partial substitution of ions, located in other sites, have been evaluated. It was established that the redistribution of cations over crystallographic sites (antistructural point defects) due to system self-organization to maintain its stability may be accompanied by cation ordering and the symmetry change of individual polyhedrons and/or the whole crystal.

NT/zeolite nanocomposites (NT - nanosized titanium(IV) oxides: η-phase and Hombifine N with anatase; zeolite: Beta(25), ZSM-5 with different modules Si/Al, MOR, or Y) have been obtained by two methods: modified cold-impregnation method (method 1) and in situ method of introduction of zeolites into the reaction mixture during the synthesis of NT by hydrolysis of TiOSO 4 ×xH 2 SO 4 ×yH 2 O or TiOSO 4 ×2H 2 O aqueous solutions (method 2), performed for the first time. According to the X-ray data, the following differences in the NT:zeolite systems under investigation have been revealed: the mixture of zeolites and NT in nanocrystalline (Hombifine N/zeolite) or amorphous states (η-phase/zeolite, except for η-phase/MOR, where NT peaks are absent) (method 1), and the mixture of Y-zeolite and amorphous NT or only Y-zeolite without NT (method 2), which indicates the different levels of interaction between NT and zeolites in the systems studied. The best characteristics of properties (photocatalytic, adsorption, and antibacterial) have been revealed in the nanocomposites synthesized by the method 2. The correlation between the photoreaction rate constant (the k value) under UV irradiation in the presence of nanocomposites ( k max for NT/ZSM-5(12)) and the type of precursor, its pH, synthesis duration, NT:zeolite ratio, organic dye composition (methyl orange or Rhodamine G) has been established. The highest degree of extraction of P(V) ions from model aqueous systems has been observed in the presence of nanocomposites with the largest total surface area of all particles ( R max = 99.48% for NT/MOR). The correlation between the sorption degree of P(V) ions and the modulus of zeolite is possible. Antibacterial activity in the dark towards Escherichia coli has been found for Y and Beta(25) zeolites and nanocomposites on their basis (methods 1 and 2) with the maximum diameter of bacterial growth inhibition (18 mm) obtained for NT/Beta(25) (method 2) synthesized only from TiOSO 4 ×xH 2 SO 4 ×yH 2 O precursor.

Calcium orthovanadate Ca3(VO4)2 (CVO) is an efficient media for laser applications. Czochralski-grown green CVO single crystals doped with over-stoichiometric 0.1 (CVO:0.1Mn) and 1.0 wt.%Mn (CVO:1.0Mn) were studied by X-ray diffraction and X-ray absorption spectroscopy for the first time. In the CVO:1.0Mn, an occurrence of Mn3+ in Ca3 (two-capped trigonal prism), Ca4 (distorted octahedron), and defective Ca5 and Ca5A (highly-distorted octahedron) sites and vacancies in V2 and V3 sites (distorted tetrahedra) were revealed. In the CVO:0.1Mn, a presence of Mn3+ in Ca3 and Ca5A sites and vacancies in V2 site were found. In the CVO, the Mn3+ form elongated octahedra (tetragonal bipyramid; coordination number, 4 + 2) typical for the Jahn-Teller ions. Models for the rearrangement of Ca3 and Ca4 polyhedra into a tetragonal bipyramid are proposed. Along with the Mn3+, the Mn2+ and Mn5+ ions were observed by optical spectroscopy in CVO:0.1Mn (predominantly Mn2+ ions) and CVO:1.0Mn (only Mn5+ ions).

PbMo@@ xW1-@@ xO4 single-crystal solid solutions with @@ x = 0.2, 0.5, 0.8 have been grown by the Czochralski method in air atmosphere from the initial charge with over-stoichiometric amount of YNbO4 (15 wt%). X-ray and neutron single-crystal and X-ray powder (Rietveld method) diffraction investigations of PbMo@@ xW1-@@ xO4 crystals indicate bulk inhomogeneity of their compositions, absence of color centers, and deviation of refined compositions from initial ones: the Nb5+ and Y3+ contents as well as oxygen vacancies content increase with increasing @@ x in PbMo@@ xW1-@@ xO4. It was found that PbMo@@ xW1-@@ xO4 with @@ x = 0.2, 0.5, 0.8, 1.0 crystallizes in the scheelite-type structure with space group @@ I41@@ /a, unlike crystal with @@ x = 0, which is characterized by the symmetry reduction to space group I 4 _ caused by ordering of oxygen vacancies. The correlation between the @@ a and @@ c unit cell parameters and composition of cation sites, dodecahedral and tetrahedral, and deficiency of oxygen site was revealed.

Lead molybdates and tungstates with general chemical formula PbTO4 (PTO), where T is Mo (PMO) or W (PWO), were grown by the Czochralski method in an oxygen (PTO-A) or inert (PTO-N2) atmosphere from a stoichiometric mixture of corresponding oxides or mixture containing an excess of PbO (PMO-N2(Pb)). The crystals were investigated by X-ray and neutron single crystal and X-ray powder (Rietveld method) diffraction methods. For PWO-A and PWO-N2 crystals, the presence of additional reflections (50%) was revealed, indicating the symmetry reduction from space group I41/a to I4_ caused by kinetic (growth) order–disorder phase transition associated with an ordering/disordering of oxygen vacancies. In the structures of PMO samples, the vacancies are absent in the Mo and O sites (PMO-A and PMO-N2) and they are present in the Pb sites (except for PMO-N2(Pb)); the defect content being higher in the PMO-N2 crystal grown in an inert atmosphere. It is shown that the light yellow color of PTO crystals is due to the O and Pb vacancies, that may be accompanied by the transition Pb2+ → Pb3+, and the gray-purple color of PMO-N2(Pb) is due to the transition Mo6+ → Mo5+. Keywords: Optical materials, Single crystals, X-ray diffraction, Neutron diffraction, Structure, Defects

Pure and Tm3+-doped Ca3(VO4)2 crystals (CVO and CVO:Tm) were grown by the Czochralski method. Activator ions were introduced in the form of Tm2O3 (0.5 and 1.0 wt%) over CVO stoichiometry. The single-crystal X-ray diffraction analysis revealed for the first time the actual crystal compositions with a splitting of one Ca5 site into two, Ca5 and Ca5A, defective sites and a partial occurrence of Tm3+ ions in two, Ca3 and Ca4, sites. X-ray absorption spectroscopy showed that the Tm3+ ions have octahedral coordination with an additional oxygen atom (coordination number, 6 + 1) and the V5+ ions have tetrahedral coordination (coordination number, 4). The structure of CVO:Tm crystals is proposed based on the local structure of Tm3+ ions, taking into account their structural organization in Tm2O3 and structural features of the CVO crystal matrix. Spectral-luminescent properties of CVO:1.0 wt%Tm crystal are consistent with structural results obtained: two pronounced peaks at λ = 470.5 and 473.5 nm in the absorption spectra (77 K), two different fluorescence spectra for different excitation wavelengths, and two components with significantly different lifetimes (1380 and 370 μs) in the decay curves indicate the presence of two different Tm3+ optical centers in the Ca3(VO4)2 crystal with excellent spectroscopic properties.

Symmetry, structural features, and point defects in the Czochralski-grown single crystals with the initial compositions CeSc3(BO3)4 (CSB-1.0) and Nd1.25Sc2.75(BO3)4 (NSB-1.25) are studied by the full-profile Rietveld method on synchrotron X-ray powder data. The space group P321 is first established and confirmed for CSB-1.0 and NSB-1.25 crystals, respectively. The features of synchrotron diffraction patterns that distinguish the space group Р321 from the R32 one are given. The site occupancies in both structures are refined and resulted in the stoichiometric composition for CeSc3(BO3)4, which coincides with the nominal composition, and the composition [Nd0.455(1)Sc0.045(39)(1)]Nd0.500(2)Sc3(BO3)4 ((Nd0.955Sc0.045(39))Sc3(BO3)4), which differs from the initial Nd1.25Sc2.75(BO3)4 one, with partial occurrence of Sc ions in one of the trigonal-prismatic sites. An analysis of literature data on single crystals with the general formula RESc3(BO3)4 (RE ​= ​Ce, Pr, Nd) together with the results of present study of powdered single crystals gives reason to exclude a crystallization of these compounds and solid solutions based on them in the space group R32. The correlation between the refined compositions of RESc3(BO3)4 crystals (RE ​= ​La, Ce, Pr, Nd), having a specific space group, and compositions of initial charge is given.

Hydrogels based on poly(N-vinyl caprolactam) (PVCL) with nanosized anatase (A particles) were synthesized by a sol–gel method and explored by powder X-ray diffraction and scanning electron microscopy. The internal structure of A/PVCL has pores smaller than those in a PVCL hydrogel. The water swelling capacity of A/PVCL is higher than that of the initial PVCL.

The possibility of using the Rietveld method for refinement of main structural parameters of both nominally pure (SBN-1) and Cr- (SBN-2: Cr2O3, 0.01 wt.%) and Ni- doped (SBN-3 and SBN-4: Ni2O3, 0.05 wt.% and 1.0 wt.%, respectively) ground relaxor-ferroelectric crystals of initial composition Sr0.61Ba0.39Nb2O6, grown by the modified Stepanov technique, has been shown. It was established that the general composition of the crystals can be described as Sr∼0.55Ba∼0.39Nb2O6−δ with possible vacancies in the oxygen sites; the composition of SBN-4 crystal differs from other samples by another distribution of Sr ions over the crystallographic sites of the structure. The correlation between the thermal parameters of oxygen atoms and the disorder on their sites as well as the Ni content in SBN-3 and SBN-4 crystals has been found. The relationship between the unit cell parameters of undoped and Cr- and Ni-doped Sr0.61Ba0.39Nb2O6 crystals and Sr and Ba content, and second-order nonlinear susceptibility values, χ(2), has been revealed.

Czochralski-grown (Na0.5Gd0.5)MoO4 single crystals doped with different concentrations of Yb3+ ions have been investigated by X-ray diffraction. The type and concentration of point defects (different Na:Gd ratios, vacancies in Mo and O sites), and, consequently, the real compositions of the investigated crystals have been determined. The presence of additional reflections (50%) for the (Na0.5Gd0.5)MoO4:10%Yb crystal was revealed, indicating the symmetry reduction from space group I41/a to P 4 _ without any change in the unit cell parameters. Crystal refinement within the framework of space group I41/a revealed an increase in the unit cell parameters for both (Na0.5Gd0.5)MoO4:3%Yb and (Na0.5Gd0.5)MoO4:10%Yb crystals; it can be explained by the kinetic phase transition of order–disorder type caused by the cation ordering at the dodecahedral sites in the local regions of the crystals. The reasons for the possible symmetry reduction in scheelite family crystals are discussed.

Composite hydrogels in the poly-N-vinylpyrrolidone – RE(NO3)3 × xH2O system with RE = La, Gd, Yb were prepared in various forms (native, native dried in the air, dried in air and ground into powder). They were studied by methods of wide- and small-angle X-ray scattering, differential scanning calorimetry, scanning electron microscopy, and electron microprobe analysis. The composition of native PVP and PVP with powdered RE(NO3)3 × xH2O includes 4 types of structural water, which content depends on the RE type. The PVP/La(NO3)3 × 6H2O surface includes “flower-like structures” consisting of whisker fragments up to 15–20 μm in size. The size of structural inhomogeneities of air-dried and then swollen in water hydrogels decreases with decreasing RE radii as well as the degree of the swelling. The antimicrobial activity (AMA) in the dark relative to Staphylococcus aureus, Escherichia coli, and Candida albicans is characteristic of all the samples. The AMA of RE(NO3)3 × xH2O (RE = La, Gd, Yb) is more effective by as compared with PVP/RE(NO3)3 × xH2O besides PVP/La(NO3)3 × 6H2O. This can be explained by different composition of particles with lanthanum on the surface of hydrogels as compared with La(NO3)3 × 6H2O. The relationship of AMA with the size of structural inhomogeneities in hydrogels, surface morphology, water content, and the role of microorganisms is not ruled out.

ZnO single crystals are related to promising direct wide band gap semiconductor materials belonging to the AIIBVI type of compounds with wurtzite structure. “Unintentional” n-type conductivity in ZnO may be caused by zinc and oxygen vacancies, and interstitial zinc atoms. To date, the comprehensive structural investigation and analysis of point defects in ZnO is absent in literature. Green, light green and almost colorless ZnO single crystals grown by the hydrothermal method in concentrated alkali solutions 4М(КОН) + 1М(LiOH) + 0.1M(NH4OH) on monohedral seeds [0 0 0 1] at crystallization temperatures in the range of 330–350 °C and pressures in the range of 30–50 MPa have been firstly investigated by neutron diffraction. It was revealed the presence of additional reflections (∼12–∼16%) for all the crystals caused by kinetic growth effects that give grounds to assign them to the space group P3 rather than to P63mc. Analysis of the refined compositions together with the color of ZnO crystals does not rule out the relationship between the color and vacancies in the zinc and oxygen positions whose concentration decreases with the discoloration of the samples. The analysis of the photoinduced variation of the total and on-axis transmittance versus the CW laser intensity showed that the colored samples have profound deep defects related to oxygen vacancies.

Crystals of strontium barium niobate solid solutions, both nominally pure Sr 0.61 Ba 0.39 Nb 2 O 6 and doped with transition metal (Cr 3+ and Ni 3+ ) ions, have been investigated by X-ray diffraction. The chemical composition of the undoped crystal was determined taking into consideration vacancies in niobium Nb(2) and oxygen sites and the statistical distribution of strontium in two (Sr(1) and Sr(2)) sites in the tetragonal tungsten bronze type crystal structure. It was established that the introduction of chromium or nickel oxides into the melt initial composition greatly influences the strontium and barium content in the crystals obtained and the distribution of these species in the crystallographic structure. The probability of finding the transition metal ions in regular and interstitial positions depending on their concentration and valence state is discussed.

The details of Tm 3+ -doped NaGd(WO 4 ) 2 single-crystal growth are discussed, the results of precise investigations of its structural and spectroscopic characteristics, as well as the analysis of cross-relaxation process of Tm 3+ ions ( 3 H 4 → 3 F 4 , 3 H 6 → 3 F 4 ) in this crystal are presented. Based on the Judd–Ofelt theory, three intensity parameters, spontaneous emission probabilities, fluorescence branching ratios and fluorescence quantum efficiency from 3 H 4 and 3 F 4 levels were refined.

Lattice parameters and crystal composition of langasite grown by the Czochralski method have been characterized in detail by X-ray diffraction (XRD) analysis. The crystal length-frequency coefficient dependence has been obtained. The frequency and elastic coefficients of langasite have been shown for the first time to be determined by the blocks disorientation in the crystal. The polarity reversal observed along the crystal was proved to be due to the stresses originating from the melt composition changes during crystal growth.

A Czochralski-grown langasite family crystals of La 3 Ga 5 SiO 14 – La 3 Ga 4 ( GaSi ) O 14 , La 3 Ga 4 [ Ga ( Si , Ge ) ] O 14 , La 3 Ga 5.5 Ta 0.5 O 14 , La 3 Ga 5.5 Nb 0.5 O 14 , and Ca 3 NbGa 3 Si 2 O 14 were studied by X-ray diffraction. Our results show that the composition of crystals may vary both axially and radially. The two solid solutions isostructural with langasite, which were identified in La 3 Ga 4 ( GaSi ) O 14 crystal studied differ in the Ga and Si occupancies on the (Ga,Si) site: Ga > Si in one solid solution, and Si > Ga in the other. The effects of the melt composition (the Ga:Si ratio, the partial substitution of Ge for Si and of M=Nb, Ta for Ga), the atmosphere (the growth in Ar or Ar+O 2 ) and heat-treatment conditions (in vacuum, in air or in oxygen) on the color (orange or colorless), the crystal composition, the structural perfection and on the polarity reversal of structure were found and explained.

The crystal and magnetic structures of RuSr2(Nd,Ce)2Cu2O10−δ (RuNd-1222) have been investigated by X-ray at room temperature and neutron powder diffraction at room temperature and T=2 K. The rotation angle of the RuO6 around the c-axis and the equatorial Ru–O(1) and apical Ru–O(2) bond lengths in these octahedra increase and the tilt angle of the RuO6 decreases upon cooling. In our measurements, we did not find any magnetic ordering of Ru moments in RuSr2(Nd,Ce)2Cu2O10−δ phase. The treatment of RuNd-1222 under oxygen pressure leads to the formation of cubic perovskite phase.

We report results of the structural, electrical and magnetic studies in synthesized (Ru1−xMox)Sr2(Gd0.7Ce0.3)2Cu2O10−δ (x=0.0, 0.25, 0.50, 0.75, 1.0) system. The RuSr2(Gd0.7Ce0.3)2Cu2O10−δ phase (x=0) may be both non-superconducting and superconducting with the transition temperature Tc(onset)=32 or 46 K depending on annealing conditions. Annealing under high oxygen pressure shifts Tc to higher temperatures that is caused by change of cation composition. In the (Ru1−xMox)Sr2(Gd0.7Ce0.3)2Cu2O10−δ system, lattice parameters of the different phases corresponding to the different composition decrease with increasing of Mo ions content. This is explained by tetrahedral coordination of Mo ions. The substitution of Mo for Ru suppresses the superconductivity: the phases with x=0.25 and 0.50 are superconductors with Tc(onset)=25 and 22 K, respectively, the phases with x=0.75 and 1.0 show a semiconductive behavior. A magnetic ordering is observed near by ∼95 K for all phases.

In this paper we report on the structural, electrical and magnetic properties of a systematic work performed on the synthesis of RuSr 2 (Nd,Ce) 2 Cu 2 O 10− δ (Ru-1222) samples that differ for the number of annealings or sintering temperature in oxygen. This is done in order to highlight the different behaviours of properties as a consequence of the treatments. In particular, we deal with the development or loss of superconductivity after oxygen treatment. Further we discuss the influence of phase composition on superconductivity and magnetic ordering.

The results of developments of new crystalline media on the basis of rare-earth scandium borates doped with Nd, Er and Yb ions and designed for use in compact diode-pumped laser systems are presented. The problems of growing these crystals by the Czochralski technique as well as their X-ray structural and optical characteristics are discussed. The data of generation tests of diode-pumped lasers with active elements from lanthanum scandium borates doped with Nd, Er and Yb and cerium gadolinium scandium borates doped with Nd are presented.

The indium-based cuprates with perovskite-like structure (In,Cu)Sr2YCu2O6+δ and (In,Cu)(Sr,Ho)2(Ho,Ce)2Cu2O8+δ, belonging to the homologous series (In,Cu)(Sr,Ln)2(Ln,Sr)k−1CukO2k+2+δ with k=1 (In,Cu-1212) and (In,Cu)(Sr,Ln)2(Ln,Ce)k+1Cu2O2k+6+δ with k=1 (In,Cu-1222) have been obtained. Their structure has been refined at room temperature using X-ray powder diffraction data. The samples with the nominal compositions (In0.5Cu0.5)Sr2YCu2Ox and (In2/3Cu1/3)(Ho1/3Ce2/3)3Sr2Cu2Ox appeared to contain phases with lattice parameters a=3.8163(1), c=11.9785(6) A (In,Cu-1212, sp. gr. P4/mmm) and a=3.8272(0), c=29.0774(3) A (In,Cu-1222, sp. gr. I4/mmm), respectively. Rietveld refinements were carried out. The real composition of these phases may be written as (In0.89Cu0.11(3))Sr2YCu2O6.98(4) (In,Cu-1212) and (In0.98Cu0.02(1))(Sr1.25Ho0.75(2))(Ho1.89Ce0.11(5)4+)Cu2.00O9.00 (In,Cu-1222). The refined composition of these phases after oxygen treatment was formal to be (In0.82Cu0.18(2))Sr2YCu2O7.00 (In, Cu ∗ -1212) and (In0.87Cu0.13(1))(Sr1.52Ho0.48(2))(Ho1.95Ce0.05(3)4+)Cu2O9.00 (In,Cu ∗ -1222). The Cu formal charge (FC Cu) in the (In,Cu)-1212, calculated from electroneutrality condition of the refined phase composition, was almost the same as before (FC Cu∼2.04) and after (FC Cu∼2.09) the oxygen treatment (underdoped phase). On the contrary, the FC Cu for the (In,Cu)-1222 increased after oxygen annealing (from −2.08 to −2.30) (overdoped phase). The non-optimal values of the Cu formal charge could be a possible reason for the absence of superconductivity in these samples.

We have investigated the synthesis, crystal structure, resistivity and magnetic measurements of phases in the Ru(Sr,Gd) 2 (Gd,Sr)Cu 2 O 8− δ (Ru-1212) and Ru(Sr,Eu) 2 (Eu,Ce) 2 Cu 2 O 10− δ (Ru-1222) systems. Rietveld refinement of the structure was carried out. The refined compositions before and after oxygen treatment are Ru 1.00(1) (Sr 1− y Gd y ) 2 (Gd 1− z Sr z )Cu 2 O 8 ( y =0.03(1), z =0.19(1)) (Ru-1212; T c 1− x Cu x )(Sr 1− y Gd y ) 2 (Gd 1− z Sr z )Cu 2 O 8 ( x =0.05(1), y =0.02(1), z =0.16(1)) (Ru,Cu-1212; T c 1− x Cu x )(Sr 1− y Eu y ) 2 (Eu 1− z Ce z )Cu 2 O 10 ( x =0.04(2), y =0.09(2), z =0.44(3)) (Ru,Cu-1222; T c 1− x Ce x )(Sr 1− y Eu y ) 2 (Eu 1− z Ce z ) 2 Cu 2 O 10 ( x =0.08(2), y =0.15(2), z =0.25(3)) (Ru,Ce-1222; T c(onset) =40 K, T c(zero) =12 K). Ruthenium atoms in these structures are octahedrally coordinated as the (Ru 5+ O 6 ) 7− species. The formal charge of Cu (FC Cu) calculated from the electroneutrality condition of refined phase composition increases after oxygen treatment and achieves an optimal value (FC Cu∼2.14) for the superconducting (Ru,Ce)-1222 phase ( t =1000°C, p =1 GPa, τ =72 h).

Two models for the crystal structure formation of perovskitelike phases in Ln-Ba-Cu-O, Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O systems are proposed. On the basis of these models all calculated phases with paramters a ≈3.8 A and c = 9–43 A were experimentally obtained. The decrease of mean distance ϵ between layers correlates with the rise of T c . The extrapolation of T c (ϵ) dependences for systems with Bi and Tl gives T max c ≈150 K at ϵ = 0.95 . On the basis of the Hume-Rothery, Matthias and Yvon criteria a new criterion for superconductivity of metal-oxide phases is proposed, based on a correlation between T c and ρ k / K electronic concentration per cation.

Magnetization M(T) and resistivity R(T) dependences have been measured on polycrystalline samples of the Pb2Re2O6+δ and Pb2−xLaxRe2O6+δ system for 0.1 < × < 1.0 in the temperature region 4.2 − 300 K. The sample of Pb2Re2O6+δ were found to be characterized by metalic-type of the electrical conductivity only. For the Pb-La-Re-O system some peculiarities of the M(T) and R(T) dependences between 8 and 50 K were found, which suggested the presence of occlusions of superconducting phase.

The results of the electric and magnetic measurements of R-Ba-Cu-O, Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O samples are reported. A deviation of the resistivity ϱ(T) and magnetic susceptibility χ(T) in the region Tc e = 2 c/aq is discussed. The extrapolation of Tc( e ) dependences for systems with Bi and Tl gives Tc = 140–150 K at e = 0.95. Although superconducting phases at e