A. A. Murashkina

Effect of doping with Co2O3, TiO2, Fe2O3, and Mn2O3 on the properties of Ce0.8Gd0.2O2−δ

The effects of Co, Fe, Mn, and Ti oxide additions on the sinterability and crystal-chemical, thermal, and electrical properties of Ce0.8Gd0.2O2−δ have been studied. The results indicate that these oxides enhance the sinterability of the mixed oxide, regardless of whether they were introduced before or after synthesis. The most effective sintering aid is Co2O3. The lattice parameters of Ce0.8Gd0.2O2−δ samples containing different metal oxide additions (1 mol %) are refined in space group Fm3m. The temperature-dependent thermal expansion data are used to determine the linear thermal expansion coefficients of the samples. Manganese oxide additions reduce the electrical conductivity of Ce0.8Gd0.2O2−δ, whereas the other dopants increase it in the order Ti < Fe < Co. The activation energy for conduction increases in the order Co < Ti < Fe < Mn.

Solid electrolytes based on CeO2 for medium-temperature electrochemical devices

CeO2-based solid solutions with a fluorite structure are promising materials as electrolytes of medium-temperature electrochemical devices: electrolytic cells, oxygen sensors, and solid oxide fuel cells. In this work, studies are presented of the effect of the dopant cation radius and its concentration on the physico-chemical properties of the Ce1 − xLnxO2 − δ solid solutions (x = 0–0.20; Ln = La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb) and also of multicomponent solid solutions of Ce1 − xLnx/2Ln′x/2O2 − δ (x = 0–0.20; Ln = Sm, La, Gd and Ln′ = Dy, Nd, Y) and Ce1 − x − ySmxMyO2 − δ (M = Ca, Sr, Ba) obtained using the solid-phase synthesis technique. Electric properties of the samples were studied in the temperature range of 623–1173 K and in the oxygen partial pressure range of 0.01–10−22 MPa. The values of oxygen critical pressure

Promising membrane materials based on strontium titanate

\left( {p_{O_2 }^* } \right)

Structural and electric properties of the Ce0.8(Sm1 − xCax)0.2O2 − δ system (x = 0.0–1.0)

are presented, at which the ionic and electron conductivity values are equal. The values were calculated on the basis of experimental dependences at 1023 K at the assumption that the ionic conductivity value is determined only by the dopant concentration and its effective ionic radius and is independent of the oxygen partial pressure.

Hydrogen production by electrochemical reforming of ethanol

Electroconductivity of SrTi1−xFexO3−δ(x = 0–0.5) specimens was studied by four-probe method. An opportunity was studied to produce hydrogen by high-temperature electrochemical conversion using SrTi0.5Fe0.5O3−δ as the membrane material of the best conductivity. The effective ambipolar conductivity values calculated for SrTi0.5Fe0.5O3−δ from the leakage experiment were found different from the ambipolar conductivity values calculated by the four-probe data processing because ambipolar conductivity corresponds to bulk transfer of complex oxide particles, taking no surface phenomena into account.

Thermal expansion and electrical conductivity of CaTi0.9M0.1O3−δ (M = Fe, Cu, Al)

CeO2-based solid solutions with a fluorite structure are promising materials as electrolytes of medium-temperature electrochemical devices. This work presents the results of systematic studies of structural and electric properties and oxygen nonstoichiometry of the Ce0.8(Sm1 − xCax)0.2O2 − δ system in a wide range of concentrations of 0 < x < 1 performed in order to establish the causes affecting the system conductivity and its behavior in a reducing medium. It is found that a single-phase solid solution of the fluorite type is formed in the whole concentration range. Parameters of its lattice cells decrease linearly at an increase in the concentration of Ca2+. Conductivity in air grows when calcium is added due to a decrease in the grain boundary resistance. The maximum conductivity in air was obtained for the composition of Ce0.8(Sm0.8Ca0.2)0.2O2 − δ and is 13.71 × 10−3 S/cm at 873 K. Studies of the dependence of conductivity of the partial pressure of oxygen showed that electron conductivity is observed at a higher oxygen partial pressure at an increase in the temperature and calcium concentration. The critical partial pressure of oxygen

CeO2 based materials doped with lanthanides for applications in intermediate temperature electrochemical devices

\left( {p_{O_2 }^* } \right)

Synthesis and electrophysical properties of (1 − x)Ce0.8Gd0.2O2 − δ + xTiO2 (x = 0–0.06) solid-state solutions

for the compositions of Ce0.8(Sm1 − xCax)0.2O2 − δ with x = 0; 0.2, and 0.5 is 1.83 × 10−16, 1.73 × 10−13, and 3.63 × 10−13 atm at 1173 K, respectively, and 2.76 × 10−21, 5.05 × 10−18, and 1.31 × 10−18 atm at 1023 K.

Electrochemical properties of ceramic membranes based on SrTi0.5Fe0.5O3−δ in reduced atmosphere

The theoretical analysis of processes occurring in the solid oxide electrochemical reformer based on the oxide conductor with mixed ion-electron conductivity has been carried out. Three versions of the preliminary conversion of the initial fuel (ethanol), namely, partial oxidation, steam reforming, and recycling by the anode effluent gas mixture have been considered. The last version is shown to feature the highest fuel conversion efficiency and hydrogen yield.

Hydrogen production aided solid oxide electrochemical reformer fed with octane : A theoretical analysis

The thermal expansion of CaTi0.9M0.1O3−δ (M = Fe, Cu, Al) samples has been measured, and their lattice parameters have been refined in space group Pnma. The three materials are shown to be mixed conductors, p-type at high oxygen partial pressures and n-type at low oxygen pressures. At intermediate oxygen partial pressures, the conductivity varies little. The acceptor dopants studied are shown to raise the conductivity of calcium titanate in the order Al < Cu < Fe.