Multiconfigurational Green's function approach with quasidegenerate perturbation theory

The new approach to approximation of polarization propagator (PP) for electronic states of atoms and molecules with reference state wave function (RSWF) constructed on the base of a multidimensional model space is presented. This approach exploiting the apparatus of the quasidegenerate perturbation theory (QDPT) is realized in the zeroth QDPT order and through the first one. The original complete system of excitation operators introduced in the approach is consistent with the RSWF by the perturbation order. This factor in conjunction with the flexibility of the RSWF creates the capabilities of balanced accounting of correlation and quasidegeneracy effects at different locations of nuclei in a molecule and for all the states concerned. In this way, the transition characteristics in electronic shells of molecules in a wide area of nuclear geometry parameters may be appropriately evaluated. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Electroconductivity of Submicron Solid Electrolytes Ce1−x GdxO2−δ as a Function of Their Density and the Gadolinium Content

The effect of the composition and density of ceramics on the electroconductivity of solid electrolytes Ce_{1 − x} Gd_xO_{2 − δ}(x = 0.09–0.31) with a submicron (0.1–0.3 µm) grain size, which are prepared from nanosized powders, is investigated. The powders are synthesized by two methods, specifically, by evaporation of a target with the aid of the radiation of a pulsed carbon dioxide laser and by a chemical method of burning. The samples of ceramics are prepared by magnetopulsed or quasi-isostatic (200–500 MPa) pressing and subsequent caking in air at a temperature of 1100–1300°C. It is established that the electroconductivity of the obtained solid electrolytes is higher and the effective activation energy for conduction is considerably lower as compared with analogous electrolytes with a micron grain size.__________Translated from Elektrokhimiya, Vol. 41, No. 6, 2005, pp. 694–701.Original Russian Text Copyright © 2005 by Ivanov, Kotov, Gorelov, Borisov, Murzakaev, Samatov, Medvedev, Khrustov, Ivin, Zayats, Balakireva, Sharova, Kuz’min, Vaganov, Moskalenko.Published on the basis of a contribution delivered at the VII Meeting on Fundamental Problems in Solid-State Ionics (Chernogolovka-2004).     

Electrochemical cell with solid oxide electrolyte and oxygen pump thereof

The paper presents the scientific basis and technical implementation of a method for obtaining oxygen by extraction from air using an electrochemical cell based on a solid oxide cell (SOC) with anion-conducting solid electrolyte. A nanopowder of a weak aggregate of the YSZ solid electrolyte and LSM fine powder was used to manufacture SOC. The electrolyte-electrode SOC structure was formed as a tube by joint pressing of functional layers and the further co-sintering at the temperature of 1200°C. The characteristics of an electrochemical cell of the oxygen pump based on a thin-wall tube of the YSZ supporting electrolyte (150 μm) with symmetrical electrodes based on LSM (∼20 μm) are studied. A prototype of a compact oxygen generator (oxygen pump) is developed and manufactured with an electrochemical part based on three serially connected SOCs. The connection is implemented in the form of metallic couplings of the Crofer 22 APU steel. The method of reaction magnetron sputtering was used to protect current leads from corrosion by applying a coating based on a Mn _x Co_{3 − x} O₄ spinel. The efficiency of a demonstration prototype at 800°C was 9 l/h at the power consumption of 50 W. The current density through SOC was 1.1 A/cm². The prototype was designed to contain no noble metal components. It is shown that the engineering approach applied allows manufacturing effective nanostructural SOCs and devices on their basis.     

EIS analysis of electrode kinetics for La2NiO4 + δ cathode in contact with Ce0.8Sm0.2O1.9 electrolyte: from DRT analysis to physical model of the electrochemical process

Journal of Solid State Electrochemistry - The oxygen reduction kinetics on an La2NiO4 + δ electrode for electrodes of different thicknesses was investigated by means of...     

Phase transition in mayenite Ca12Al14O33

A phase transition in Ca₁₂Al₁₄O₃₃ has been discovered and investigated by thermogravimetric analysis, differential scanning calorimetry, dilatometry, and high-temperature X-ray diffraction. The phase transition occurs at 922 ± 45 K (??H = ?406 ± 13 kJ/mol, ??S = ?440 ± 14 J/(mol K)) and is presumably a first-order one. It does not change the symmetry of the cationic subsystem. The phase transition is difficult to reveal because the material changes its mass, probably by releasing water bound in several different ways.     

Nanostructured composite materials of cerium oxide and barium cerate

Nanosized powders with a composition of (1-x)Ce_0.8Sm_0.2O_2-δ-xBace_0.8Sm_0.2O_3-δ (x = 0, 0.3, and 1) were obtained by self-ignition combustion synthesis (SICS) from the appropriate nitrates and various organic fuels (glycine, glycerol, citric acid, and a mixture of citric acid and ethylene glycol). The most finely dispersed powders formed when the concentration of the perovskite phase in the system decreased or when glycerol or citric acid-enthyleneglycol mixture was used as a fuel during SICS. A procedure for the preparation of powders and nanostructured ceramics was developed and their electric properties were studied.     

Fabrication of Microtubular Solid Oxide Fuel Cells by Film Compaction and Co-Sintering

The microtubular design of solid oxide fuel cells (SOFCs), which are promising electrochemical power sources, has a number of significant advantages over traditional planar and tubular designs: increased resistance to the cell (stack) heating rate and packing density of cells in a stack. The paper presents results on the development of a microtubular SOFC (MT-SOFC) fabrication method based on compaction and co-sintering a set of films. The formation of an anode-supported MT-SOFC having a Ni-cermet collector (support) and functional layers of about 300 and 50 μm thick, respectively; a Zr_0.84Y_0.16O_2–δ solid electrolyte layer (40 μm); and a cathode based on La_0.7Sr_0.3MnO_3–δ has been developed. The outer diameter and length of the MT-SOFC were 3.9 and 12 mm, respectively. The maximum specific power generated by the MT-SOFC at 850°C was 0.21 W/cm².