N. A. Zhuravlev

Optical absorption and nuclear magnetic resonance in lithium titanium spinel doped by chromium

The optical absorption and nuclear magnetic resonance spectra of Li4 − xCr3xTi5 − 2xO12 (x = 0, 0.01, 0.02, 0.04) solid solutions have been investigated. It has been found that, in the Li4Ti5O12 spinel, lithium ions migrate from tetrahedral to octahedral positions with increasing temperature. Doping of chromium to the spinel favors an increase in the fraction of tetrahedrally coordinated lithium and hinders diffusion.

Features of the local structure of hydrated fluorine-substituted solid solutions based on Ba2In2O5

It is found for hydrated solid solutions of Ba2−0.5xIn2O5−xFx · nH2O, Ba2In2O5−0.5yFy · nH2O (0 ≤ x ≤ 0.30; 0 ≤ y ≤ 0.24) that increasing the concentration of fluorine lowers the degree of hydration. The composition of proton-containing groups and the places of their localization in the structure of hydrated oxyfluorides are determined. The presence of fluorine in the complex oxide’s structure helps increase the mobility of protons.

Finely dispersed phases of MO(OH)2 (M = Zr, Hf) oxyhydroxides

We discuss studies of new finely dispersed phases of zirconium and hafnium oxyhydroxides MO(OH)2 (M = Zr, Hf) by means of X-ray diffraction, NMR, Raman scattering, IR spectroscopy, electronic microscopy and thermal analysis. It is demonstrated that these compounds and their precursors (lithium salts obtained by citrating) are isostructural. Hafnium oxyhydroxide is thermally more stable than its zirconium analog and decomposes at approximately 260°C.

Synthesis and Characterization of the LiMnP1–xVxO4–δ Solid Solutions

Compounds with the olivine-type structures are considered as perspective materials for lithium-ion power sources for both industrial and transport applications. Lithium iron phosphate is most highly developed from this family, but LiMnPO4 is supposed as much promising, due to its higher EMF vs. lithium. One of the main lacks of this class of materials is the low electronic conductivity. The traditional ways of conductivity increase by partial replacement of Mn with other transition metal for LiMnPO4 do not result to essential success. Our approach consisting in the influence onto anion sublattice results to better effect. Such solid solutions should be suitable for oxygen nonstoichiometry creation in virtue of ability of vanadium ion for oxidation degree downturn. Using magnetic methods, we succeeded to show that the required solid solutions are really formed. The optimal synthesis conditions of LiMnP1-xVxO4-δ solid solutions were determined. It was shown, that the doping of LiMnPO4 by vanadium jointly with oxygen nonstoichiometry brings to substantial enhance of electronic conductivity in this material. Observed peculiarities of the magnetic properties indicate the restructuring in the local environment in anion sublattice.

Influence of dispersion on the physicochemical properties of metatitanic acid

Li2TiO3 and H2TiO3 samples with various degrees of dispersion were investigated by X-ray diffraction, NMR spectroscopy, and electronic microscopy. It was shown that H2TiO3 has a distinct structure and exhibits high sorption activity in relation to rare earth elements. The sorption activity of H2TiO3 grows due to the increase in specific surface of samples.

NMR in Li 2 M 3 Al(MoO 4 ) 4 Triple Molybdates (M = Rb, Cs)

Nuclear magnetic resonance (magic angle spinning) spectra of 7Li, 27Al, 87Rb, and 133Cs nuclei are measured in Li2M3Al(MoO4)4 triple molybdates (M = Rb, Cs) for the first time. Analysis of the nuclear magnetic resonance spectra reveal considerable asymmetry in the distribution of the electric charge throughout the crystal lattices of the compounds.

Synthesis and physicochemical properties of Li2MexZr1 − xO3 − δ (Me = Nb, Ti; x = 0.05, 0.1) solid solutions

Complex lithium metallates Li2MexZr1 − xO3 − δ (Me = Nb, Ti, x = 0.05, 0.1) with iso-and heterovalent substitutions for Zr4+ ions in lithium zirconate are synthesized for the first time using a citrate technique. The inclusion of Ti4+ and Nb5+ ions in the crystal structure of Li2ZrO3 is confirmed by means of X-ray diffraction and NMR. It is shown that in the temperature range of 750–820 K, Li2Ti0.1Zr0.9O3 solid solution has higher conductivity than phases of undoped lithium zirconate.

51V NMR in Mn2−2xNi2xV2O7 solid solutions

Abstract51V NMR, DTA, and thermogravimetric analysis are used to study the thermal behavior of a manganesenickel pyrovanadate complex Mn2−2xNi2xV2O7. It is shown that the nature of 51V hyperfine interactions in manganese pyrovanadate and solid solutions based on its polymorphic modifications is specified by the structurally activated oxygen exchange with the gaseous phase.

Stabilizing the triclinic structure of Mn2V2O7 via isovalent cationic substitution

The thermal expansion of Mn2V2O7 in the temperature range of −190 to 1030°C is studied. The volumetric thermal expansion coefficients for triclinic (α) and monoclinic (β) modifications are 2.57 × 10−5 and 3.86 × 10−5 1/deg, respectively. It is shown that as the Ni2+ concentration in Mn2−2xNi2xV2O7 rises, the point of the α → β phase transition point moves from room temperature for Mn2V2O7 to 155 ° 5°C for Mn1.46Ni0.54V2O7 (27 mol % Ni2V2O7).

Studying the local structural features of Zn2 − 2xCd2xV2O7 by NMR and IR spectroscopy

The local structure of pyroanion groups in the incommensurate phase X-Zn2 − 2xCd2xV2O7 (0.11 ≤ x ≤ 0.48) with a zero volumetric expansion coefficient is studied. Comparative analysis of IR and NMR spectra of samples in the X-phase and of ZnCdV2O7 revealed that vanadium atoms have a similar structural and an identical charge environment. Additional bands in the IR spectra of the X-phase in the range of end vibrations are due to the influence of the cation sublattice.