G. N. Mazo

Nanocomposites based on LaCoO3 and mesoporous molecular sieves: Preparation and physicochemical and catalytic properties

Individual perovskite-like LaCoO3 obtained by the citrate method and LaCoO3 supported onto the mesoporous molecular sieve MSM-41 have been characterized by X-ray powder diffraction, EPMA, low-temperature nitrogen adsorption, H2 TPR, and EXAFS. The catalytic activity of the supported cobaltate in methanol oxidation is two orders of magnitude higher than the activity of the bulk cobaltate owing to nanosized LaCoO3 particles in the pores of the molecular sieve.

New selective catalysts of oxidative conversion of methane to synthesis gas

ISSN 00125016, Doklady Physical Chemis try, 2011, Vol. 441, Part 2, pp. 233–236.

Oxygen mobility in layered cuprates La2−xSrxCuO4−δ

Abstract Oxygen mobility in layered lanthanum cuprates La 2− x Sr x CuO 4− δ is studied by dynamic-thermal isotope exchange method and coulometric titration. Depending on the temperature, different preferred surface exchange reactions are realized. Such characteristics of bulk diffusion process as activation energy and diffusion coefficient are stated for the cuprates. Theoretical modeling of diffusion process in La 2 CuO 4 and LaSrCuO 3.5 phases is carried out using molecular dynamics simulations. The data obtained are compared to the ones previously obtained experimentally.

Lanthanum-strontium cuprate: A promising cathodic material for solid oxide fuel cells

Samples of lanthanum-strontium cuprate LaSrCuO3.61 are synthesized by a solid-phase method at 1473 K, in air. Electron diffraction patterns reveal low-intensity satellites whose position is described in the reciprocal space by the (3 + 2)-dimensional space group I4/mmm(αα0, α-α0)00mg. Using a five-layer cell LaSrCuO4-δ|YSZ|LaSrCuO4-δ|YSZ|LaCuO4-δ prepared by isostatic hot pressing, the ionic component of conductivity of LaSrCuO4-δ is determined (σ1179 K = 3.8 × 10−3 S cm−1), which is commensurate with other mixed conductors based on complex oxides of cobalt and iron.

The synthesis and transport properties of the cuprates La2 − xSr1 + xCu2O6 + δ

The cuprates La2 − xSr1 + xCu2O6 + δ(x = 0, 0.1, 0.2) are synthesized by solid-state method. Their dc conductivity was studied over the 373 to 1173 K temperature range and 10 to 2.1 × 104 Pa oxygen partial pressure range by using four-probe technique. It is shown that the cuprate conductivity in air is maximal at ∼673 K; it is 60 S/cm for La2SrCu2O6.09; 68 S/cm, for La1.9Sr1.1Cu2O6.18; and 81 S/cm, for La1.8Sr1.2Cu2O6.10. The thermal expansion coefficient of La2SrCu2O6.09 is determined by thermomechanical method and high-temperature X-ray diffraction method; its value (16 ppm K−1) shows that the material is compatible with the ceria-based solid electrolytes during the thermal cycling.

Prediction of transport properties of new functional materials based on lanthanum-strontium cuprates: Molecular mechanics calculations

The method of molecular dynamics is used for prediction of properties of new functional materials based on lanthanum-strontium cuprates La2 − xSrxCuO4 − δ as new materials of the solid state ionics. The most interesting phases are synthesized to test the obtained calculation data and their electrophysical and thermomechanical characteristics are studied. It is shown that the high values of the oxygen diffusion coefficients are obtained in the La2 − xSrxCuO4 − δ solid solutions with a high replacement degree of Sr → La (up to x = 1). The calculated values of lattice cell parameters, thermal expansion coefficients and oxygen diffusion coefficients agree with the experimental data. The observed anisotropy of anionic transport for all the studied compositions corresponds to the regularities of crystal structure of complex oxides. Using the molecular dynamics method allows tracing the contribution of separate types of oxygen ions (equatorial and apical) into ionic transport at the microscopic level and also confirming directly that oxygen diffusion occurs according to the usual jump mechanism, mainly in (CuO2) layers.

Drastic change of electrical conductivity in Pr2CuO4 by isovalent La doping

How to affect the transport properties of complex oxides was considered using the uncommon example of Pr2−xLaxCuO4. It was established that appropriate La doping in Pr2CuO4 leads to a noticeable increase in high-temperature electrical conductivity. The reason for such changes are discussed from the viewpoint of possible charge redistribution in Pr2−xLaxCuO4.

Features of high-temperature behavior in NdCaCoO4—the catalyst of the partial oxidation of methane to syngas

The peculiarities of the high-temperature (373–1173 K) behavior and transport properties of NdCaCoO4, which is a highly active and selective catalyst of the partial oxidation of methane to syngas, were considered. A relationship between its thermal and electrophysical properties and the structure and defectiveness of the oxygen sublattice was found. The electric conductivity of this compound, which is a two-dimensional analog of perovskite, was found to be almost independent of the oxygen pressure (

Synthesis of LaSrCuO4−δ at reduced temperatures

p_{O_2 } = 10^{ - 4} - 1