R. M. Zakalyukin

On polymorphism and morphotropism of rare earth sesquioxides

The data on the phase transitions in the series of rare earth sesquioxides are considered in terms of the thermodynamic theory of morphotropism. It is shown that the scheme of polymorphism and morphotropism suggested by V.V. Glushkova is the most adequate. The derivatographic dehydration of lanthanum and neodymium oxide hydrates is performed. The transition of the cubic C modification into the hexagonal A modification of neodymium oxide is accompanied by the removal of volatile impurities and, thus, is not a polymorphic transition proper.

Incorporation of alkali impurities into single crystals of barium metaborate β-BaB2O4

The impurities in single crystals of the low-temperature β modification of BaB2O4 grown from flux in the BaB2O4-Na2O system have been studied. The β-BaB2O4 compound was examined by X-ray powder diffraction analysis. The appearance of scattering centers in the crystals correlates with the high content of sodium whose critical concentration is about 0.021 wt %. The effective distribution coefficient of sodium is 2.5–4.4 × 10−3. The conditions for constitutional supercooling at the crystallization front are considered.

Physical Properties of Fluoride Glasses for Ionics

The ionic conductivity and permittivity of glasses based on ZrF4, BaF2, LaF3, AlF3 and NaF (ZBLAN) or PbF2, InF3, BaF2, AlF3 and LaF3 (PIBAL) are studied. The influence of the glass composition on the glass transition temperature (Tg) and on the crystallization temperature (Tx) is reported. For all ZBLAN glasses the temperature dependencies of the ionic conductivity are close one to another (s500 = 8(2)·10-6 S/cm) and their conduction activation enthalpies are equal to 0.82(1)eV. From the point of view of the ionic conductivity, the best glass compositions are the PIBAL50 (50 m/o PbF2) and PIB45 ( 45 m/o PbF2).

Ba1−x R x F2 + x Phases (R = Gd-Lu) with distorted fluorite-type structures—products of crystallization of incongruent melts in the BaF2-RF3 Systems (R = Gd-Lu). III. Defect Ba0.75Lu0.25F2.25 structure. A new {Lu8[Ba6F71]} supercluster of defects

AbstractThe structure of Ba0.75Lu0.25F2.25 crystals grown from melt has been studied by X-ray diffraction analysis (4729 measured reflections, 269 independent reflections with I > σ (I), R = 1.1%, Rw = 0.7%). The crystals are crystallized in the cubic system, sp. gr. Pm

The influence of a magnetic field on the microhardness of K, Rb, Cs, NH4, and Tl acid phthalate crystals

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One-dimensional SnF2 single crystals in the inner channels of single-wall carbon nanotubes: I. Preparation and basic characterization

m, with the lattice parameter a = 5.9870(9) Å. A new complex of defects is singled out—a supercluster of the composition {R8[Ba6F71]}. This supercluster differs from the well-known rare earth octahedral supercluster of the composition {Ba8[R6F68-69]} because its nucleus is formed not by RE cations but by an alkali earth cation, Ba. The {R8[Ba6F71]} supercluster has a configuration close to that of the [B14F64] fragment of the fluorite structure and can replace the latter isomorphously. The model of the Ba0.75Lu0.25F2.25 crystals consisting of coherently intergrown isostructural microphases having different chemical compositions is characterized by the good agreement of the calculated and experimentally determined occupancies of the F1− positions. The comparison of the Ba0.8Yb0.2F2.2 (phase studied earlier) and Ba0.75Lu0.25F2.25 structures demonstrates the evolution of the defect structure along the series of rare earths with the corresponding change of the sp. gr. Fm

One-dimensional SnF2 single crystals in the inner channels of single-wall carbon nanotubes: II. Structure and nanocomposite construction modeling

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