V. V. Kireev

Refinement of the crystal structure of Na2Ti3O7

The crystals of Na2Ti3O7 were obtained by crystallization from flux. The structure of the compound was refined from X-ray diffraction data collected on a four-circle diffractometer (2θ/θ scanning technique, λMoKα radiation, graphite monochromator, θmax = 40°). The crystals are monoclinic a = 9.133(2) Å, b = 3.806(1) Å, c = 8.566(2) Å, β = 101.57(3)°, sp. gr. P21/m, Z = 2, ρcalcd = 3.435 g/cm3, R = 0.035, 1241 reflections with I ≥ 2σ(I). The geometric characteristics of the Ti-polyhedra are analyzed as to their positions in the trioctahedral ribbon. The polymorphism of the {Ti3O7}2− anionic radical in the structures of Na2Ti3O7 and PbTi3O7 is described. The topology and dimensionality of the { Ti3O7}2− anionic radical are demonstrated to depend on the type of the large cations located at the lattice points of the hexagonal close packing characteristic of both structures.

Growth and ionic conductivity of γ-Li3PO4

Single crystals of γ-Li3PO4 have been grown from flux. The 4 × 8 × 9-mm crystals have the cleavage along the [010] and [120] directions. The anisotropy in ionic conductivity in the grown crystals, ((σ ‖ a)/(σ ‖ b) = 2.5 and (σ ‖ a)/(σ ‖ c) = 1.3), is explained by specific features of the γ-Li3PO4 structure.

Growth of thin ZnO films by ultrasonic spray pyrolysis

We report the growth of high-quality thin ZnO films with controlled microstructure on Si(111) substrates by ultrasonic spray pyrolysis of Zn-containing solutions.

Refinement of crystal structure of a Ge-analogue of natisite Na2{TiGeO4} and prediction of new phases with anionic {MTO5} radicals

The crystal structure of the synthetic Ge-modification of the mineral natisite, Na2{ TiOGeO4}, has been refined by X-ray diffraction method (a four-circle diffractometer, 2θ/θ scanning, MoKα-radiation, θmax = 50°: a = 6.658(1), c = 5.161(1) Å, sp. gr. P4/nmm, Z = 2, ρcalcd = 3.58 g/cm3, R1 = 0.030, s = 1.131, wR(F2) = 0.058 (352 reflections with I≥2σI). The comparative crystallochemical analysis of the related (including hypothetical) phases with the anionic {MTO5} radicals (M = Ti, V, Ge; T = Ge, Si, P) is performed with the aim of revealing a possible relationship between the composition and the structure type of the compounds.

Growth, Structure, and Electrophysical Properties of Single Crystals of A2TiGeO5 (A = Li and Na)

Crystals of Li2TiGeO5 were obtained by solution-melt crystallization, and those of Na2TiGeO5 were grown from a melt by pulling. The crystals are isostructural with the natisite mineral Na2TiSiO5. The crystal structure of Li2{TiOGeO4} was refined by X-ray diffraction analysis (a four-circle diffractometer, 2θ/θ scan mode, MoKα radiation, θmax = 50°). The unit cell parameters are a = 6.614(4) Å and c = 4.435(4) Å; space group P4/nmm, Z = 2, ρcalcd = 3.67 g/cm3, R = 0.031, s = 1.128, wR(F2) = 0.071 (548 reflections with I ≥ 2σI). The ionic conduction in both crystals was found to be anisotropic in the temperature range 250–600°C;. At 400°C;, the conductivity values are 10–4 to 10–5 S/cm along the a axis and 10–6 to 10–8 (for Na2TiGeO5) and 10–7 to 10–9 S/cm (for Li2TiGeO5) along the c axis.

Thin films of ZnO:M synthesized by ultrasonic spray pyrolysis

High optical quality ZnO:M@Si nanocomposites (where M is the doping element) were obtained by ultrasonic spray pyrolysis. The variation of experimental conditions, the use of various precursors and dopants demonstrated that the morphology of zinc oxide nanoparticles is mainly determined by the sort of the doping element. The luminescence spectra confirm indirectly the isomorphous incorporation of the dopant ions into the zinc oxide lattice.

Mixed tetrahedral anionic framework in the K3Ga2(PO4)3 crystal structure

The crystal structure of a new synthetic potassium gallophosphate K3Ga2(PO4)3 grown from a solution in the melt of a mixture of GaPO4 and K2MoO4 is determined using X-ray diffraction (Bruker Smart diffractometer, 2θmax= 56.6°, R = 0.044 for 2931 reflections, T = 100 K). The main crystal data are as follows: a = 8.661(2) Å, b = 17.002(4) Å, c = 8.386(2) Å, space group Pna21, Z= 4, and ρcalcd = 2.91 g/cm3. The synthesized crystals represent the third phase in the structure type previously established for the K3Al2[(As,P)O4]3 compound. It is shown that the structure consists of a three-dimensional anionic microporous tetrahedral framework of the mixed type, which is formed by PO4 and GaO4 tetrahedra shared by vertices. Large-sized cations K+ occupy channels of the zeolite-like framework. The crystal chemical features of the formation of structure types of compounds with mixed frameworks described by the general formula A3+M23+(TO4)3 (where A = K, Rb, (NH4), Tl; M = Al, Ga, Fe, Sc, Yb; T = P, As) are analyzed.

Atomic structure and mechanism of ionic conductivity of Li3.31Ge0.31P0.69O4 single crystals

The atomic structure of Li3.31Ge0.31P0.69O4 single crystals was refined based on high-precision X-ray diffraction data at 293 K. The characteristic features of the crystal structure are considered, and their influence on high ionic conductivity (Li+) of these crystals is discussed.

Growth and ionic conductivity of Li3 + xP1 − xGexO4 (x = 0.34) single crystals

Li3 + xP1 − xGexO4 crystals (x = 0.34) with dimensions of about 3 × 3 × 5 mm3 were grown for the first time from flux. The conductivities of the crystals measured along three directions have close values and are equal to σ ≈ 1.8 × 10−6 and 3.7 × 10−2 Sm/cm at the temperatures 40 and 400°C, respectively (similar to the case of pure lithium phosphate, somewhat lower values of electric conductivity were measure along the b axis). The activation energy of conductivity is equal to 0.54 eV. A considerable increase in the conductivity of the solid solution in comparison with the conductivity of pure lithium phosphate is explained by the specific features of the lithium sublattice in the crystal structure of the λ-Li3PO4 type.