The paper studies the electronic structure of proton-conducting oxides based on the lanthanum scandate La_1-xSr_xScO_3-x/2 for advancing in understanding the mechanisms of hydrogen uptake from dry and humid atmospheres into the lattice of oxides with a perovskite structure. The process of protons incorporation from watercontaining atmospheres is considered to describe by the reaction H₂O+ O_O^× +V_O^** = 2OH_O^*. However, there is no established concept of a mechanism for proton uptake from a dry hydrogen atmosphere. At such an uptake, a positively charged proton defect will be formed in the oxide lattice, and a negative charge must appear for compensation of the excess positive charge. Formally, the reaction of such process can be represented as 1/2 H₂O+ O_O^×=OH_O^*+e'. In this case, an uncompensated electron appears, and the question arises as to where it is localized. In order to answer this question, it is necessary to study the electronic structure of perovskites. With increasing in concentration of dopant x, the absorption band at 5.6 eV overlapping with the edge of fundamental absorption is found to increase. A similar band has been observed in other proton-conducting perovskites, and it can be related either with oxygen vacancies or with acceptor levels, since the amount of both the ones increases with the concentration of dopant x. When protons are incorporated from the dry hydrogen atmosphere into the La_1-xSr_xScO_3-x/2 lattice, the absorption intensity in this band decreases, that can be due to the transition of the defects causing this band to another charge state. In addition, specific defects that absorb light in the red and infrared region at hν < 2.2 eV are formed. They are found to be located deep enough in the bang-gap and not to be the electronic traps. It is also shown that in La_1-xSr_xScO_3-x/2 there are electron traps located at a depth of 2 eV to 4.5 eV in the band-gap relative to the bottom of the conduction band. On the basis of the data obtained, it can be assumed that these defects are somehow associated with oxygen vacancies, but their charge state is not obvious. It is important that these traps participate in the capture of uncompensated electrons during the proton uptake from the dry hydrogen atmosphere.

Ceramic solid proton electrolytes La_0,99Ca_0,01NbO₄, Nd_5,5WO_11,25-δ и Nd_5,5W_0,5Mo_0.5O_11,25-δ were synthesized and their proton conductivity was measured in the temperature range of 300-650 оС in an atmosphere of dry and humid air. Solid electrolytes are shown to have a high proton conductivity ~ 10^-4 S/cm at 500 оС. Dense metal-ceramic composites containing phases of metal Ni_0,5Cu_0,5 and oxides Nd_5.5WO_11.25 or Nd_5.5W_0.5Mo_0.5O_11.25-δ with the typical total conductivity of metals were obtained using hot pressing technique an argon atmosphere. The problem arises with an experimental determination of the ionic (in this case proton) conductivity contribution to the overall conductivity of the material comprises when studying the metal-ceramic materials properties. The proton conductivity values can be estimated from the results of studying the hydrogen permeability of membranes and the diffusion of hydrogen; however, these methods are rather complicated in instrumentation. Therefore the use of relatively simple and accessible electrical measurement methods to solve this problem is very relevant. In this paper, the partial proton conductivity of the composite materials mentioned above was first measured using a 4-electrode cell with ion probes made of a ceramic proton conductor La_0,99Ca_0,01NbO₄in an atmosphere of moist hydrogen and at the temperature range of 300-650 оC. In the low temperature region, the partial proton conductivity values measured in the 4-electrode cell are in good agreement with those obtained by standard complex impedance analysis for the pure ceramics not containing metal. In high temperature region, the values obtained by two independent techniques differ. This can be explained by the contribution of the electrochemical reaction proceeding at the interface between the ion probe and the metal phases and accompanied by the dissolution of atomic hydrogen in the metal. In general, the measured value of the ionic conductivity can be either underestimated or overestimated in comparison with the real one, depending on the rate of chemical reactions occurring at the electrodes. Nevertheless, in a limited temperature range, the use of four-electrode measurements with ionic (proton) probes allows one to obtain correct results.

Based on LaScO₃ proton-conducting oxides with a perovskite structure, having high chemical stability to water vapor, are promising proton electrolytes for SOFC, but they are poorly studied in the form of thin films. Lanthanum-strontium manganite is one of the most common materials for the SOFC cathode. The aim of this work is to study the effect of the La_0.6Sr_0.4MnO_3-α cathode substrate composition on the properties of La_1-xSr_xScO₃ (0.01, 0.05 and 0.10) thin-film proton electrolytes, obtained by simple centrifugation of the film-forming solution. The properties of La_1-xSr_xScO₃ in the form of ceramic and thin-film samples are compared. The experiment showed that the films La_1-xSr_xScO₃ at 5–30-fold deposition on cathode substrates form continuous coatings with a grain size of 50–200 nm, which do not contain transverse pores. These results have a fundamental importance for the development of SOFC with ultra-thin film electrolyte on a supporting electrode. Under dry and wet air, the electrical conductivity of La_0.6Sr0.4MnO_3-α/ La_1-xSr_xScO₃ /Pt cells is found to be bulk conductivity and to rise with increasing atmospheric humidity which indicates an increase in the contribution of proton conductivity. In this case, the grain-boundary resistance of the material and the polarization resistance of the electrodes are practically not realized. The conductivity of LSS films is 1–2 orders of magnitude higher than the bulk conductivity of ceramic samples of similar composition and has low activation energy. The observed differences in the conductive properties of films are explained by the interaction of related perovskites of the scandate and lanthanum manganite. The data obtained may be of interest to specialists in the fields of hydrogen energy, electrochemistry, materials science, the development of electrochemical devices: sensors and fuel cells.

The complex oxides with a perovskite-like structure stable in a wide range of partial pressures of oxygen and temperatures have successfully proven themselves as a promising material suitable for use as an electrolytic material of solid oxide fuel cells. Optimization of their transport properties is achieved by various kinds of substitutions. Today the cationic doping is the most studied method. A new promising method is anionic doping, which allows discovering fundamentally new ways to modify the structure and properties of compounds. In order to understand the consequences of the anion dopant influence on transport properties and to reveal general patterns of proton transfer, the paper studies the fluorine and chlorine-substituted solid solutions based on perovskite Ba₄Ca₂Nb₂O₁₁ and brownmillerite Ba₂In₂O₅. The paper presents the results of investigation of thermal and electrical properties, and discusses the influence of the halogen dopant nature on the degree of hydration and partial (О ^2- , Н ⁺ ) conductivity, as well as the mobility of protons. The Fand Clsubstituted phases based on oxygen-deficient compounds were synthesized by solid state method: the double oxide Ba₄Ca₂Nb₂O₁₁ and the brownmillerite Ba₂In₂O₅. The halogen doped phases of Ba₄Ca₂Nb₂O_10.95Х_0.1 and Ba₂In₂O_4.95 Х₀.₁ (X = F, Cl) were found to be capable of reversible water uptake and the formation of proton defects ОН_О^* . The analysis of the oxygen ion conductivity has been performed. The introduction of the donor dopant, both F_О^* and Cl_О^* , was found to lead to an increase in the oxygen conductivity in both the double perovskite and brownmillerite due to the appearance of the effects of additional electrostatic repulsion of the donor dopant with oxygen vacancies V_o^**. The study of proton transfer showed a sympathetic change in the proton and oxygen ionic conductivities in doped Ba₄Ca₂Nb₂O₁₁ which allows one to speak of the influence of the dynamics of the oxygen sublattice on proton transport: F- and Cl-doped phases with greater oxygen mobility are characterized by large proton conductivities in comparison with the matrix composition. For doped brownmillerite Ba₂In₂O₅, the introduction of F ions led to an increase in the proton mobility, and the presence of Cl-dopant led to a decrease due to a change in the ionicity of the metal halogen bonding and the associated increase in the degree of covalence of the neighboring metal oxygen bondings. The method of anionic doping described in the paper demonstrates a new strategy for increasing oxygen-ion and proton conductivities in perovskites and perovskite-like compounds.

One of the priority direction in the field of electrochemical devices for generating electricity is the development of solid oxide fuel cells (SOFC) operating at lower temperatures (below 600 ºC). The methods of forming a film electrolyte membrane are actively investigated when an improvement in the performance characteristics of the device occurs due to a decrease in the thickness of the electrolyte layer. As the electrolyte material of SOFC, zirconium oxide based on the solid solutions are most often used which have sufficient oxygen conductivity, chemical durability, and stability of physical properties in both oxidation and reducing atmospheres. The paper explores the yttria-stabilized zirconium oxide (YSZ) thin films prepared by dip-coating of NiO-YSZ substrates in an aqueous suspension followed by heat treatment and deals with some regularities of the crystallization of films on electrode substrates depending on the method of preparation of film-forming suspension, the surface morphology of the substrate, and heat treatment conditions of the film deposition. Optimum conditions for obtaining gastight film deposition on substrates with different porosity are determined. The effect of the components composition of the suspension (concentration of YSZ, dispersant), viscosity and pH of the system on the formation of film electrolyte was studied. Varying these parameters allows the YSZ film to be deposited with a thickness of 5–10 μm without cracks for 1–2 application cycles. The use of metal-ceramic compositions as anode materials due to the presence of the electrolyte phase is shown to increase the mechanical strength of the supporting electrode and provide more favorable conditions for the formation of the electrolyte film. The metal component is responsible for good electrophysical characteristics. For SOFC with an oxygen-ion electrolyte based on stabilized zirconium oxide, we discuss the composite anodes containing NiO and, accordingly, after reduction Ni as the metallic phase. This method is a simple and cost-effective for manufacturing a thin film electrolyte for solid oxide fuel cell.