Perovskite-related oxide materials for oxygen-permeable electrochemical membrans

This brief review is focused on the studies of mixed ionic-electronic conductors on the basis of lanthanum gallate doped with transition metal cations in the В sublattice. The substitution of gallium with iron, cobalt or nickel results in greater electronic conductivity, simultaneously keeping high level of the oxy-gen ionic transport. In particular, La0 90Sr0 10Ga0 65Ni0 20Mg0 1503d perovskite exhib-its attractive oxygen permeability, which is quite similar to that of La2Ni04- and (La,Sr)Co03-based phases The combination of appropriate transport and thermomechanical properties with sufficiently high thermodynamic stability en-ables to use Ni- or Fe-substituted LaGa03-based mixed conductors for the mem-brane electrocatalytic reactors for partial oxidation of light hydrocarbons

Some Stationary Deformation Problems for Compound Shells of Revolution

A common approach to solving stationary deformation problems for compound systems composed of shells of revolution with different geometry and structure is developed. The approach is based on the use of shell models with different level of rigor and of the general numerical-analytical technique for solving corresponding problems. The examples of studying the subcritical stress-strain state, vibrations, and dynamical instability of complex form systems are presented, features of their deformation are notedA common approach to solving stationary deformation problems for compound systems composed of shells of revolution with different geometry and structure is developed. The approach is based on the use of shell models with different level of rigor and of the general numerical-analytical technique for solving corresponding problems. The examples of studying the subcritical stress-strain state, vibrations, and dynamical instability of complex form systems are presented, features of their deformation are noted

Perovskite-related oxide materials for oxygen-permeable electrochemical membrans

This brief review is focused on the studies of mixed ionic-electronic conductors on the basis of lanthanum gallate doped with transition metal cations in the В sublattice. The substitution of gallium with iron, cobalt or nickel results in greater electronic conductivity, simultaneously keeping high level of the oxy-gen ionic transport. In particular, La0 90Sr0 10Ga0 65Ni0 20Mg0 1503d perovskite exhib-its attractive oxygen permeability, which is quite similar to that of La2Ni04- and (La,Sr)Co03-based phases The combination of appropriate transport and thermomechanical properties with sufficiently high thermodynamic stability en-ables to use Ni- or Fe-substituted LaGa03-based mixed conductors for the mem-brane electrocatalytic reactors for partial oxidation of light hydrocarbons

Mixed conductivity in La(Ga,Mg,Nb)O_3-δ Perovskites

Solid-solution formation has been found in the perovskite-type system LaGa0.85-xMg0.15(Nb0.33Mg0.66)xO3-δ (x = 0 - 0.20). Increasing dopant concentration leads to lower oxygen ionic conductivity and, at temperatures above 1000 K, higher p-type electronic conductivity. Oxygen-ion transference numbers in air were determined to vary in the range 0.78 to 0.96, decreasing with increasing x and temperature. Thermal expansion coefficients of ceramic samples of LaGa0.85-xMg0.15(Nb0.33Mg0.66)xO3-δ were calculated in a temperature range of 300 to 1100 K to be essentially independent of composition, varying in the range (10.0 ± 0.2) x 10-6 K-1. Values of the activation energy for the total electrical conductivity in air are 104-106 kJ/mol in the temperature range 670 - 1000 K and 67 - 76 kJ/mol in the temperature range 1000 - 1200 K. The method of synthesis was found to affect both the symmetry of the perovskite unit cell and phase composition. The presence of second phases led to a dramatic decrease in conductivity.Se ha encontrado la formación de una solución sólida en el sistema LaGa0.85-xMg0.15(Nb0.33Mg0.66)xO3-δ (x = 0 - 0.20). Un aumento de la concentración de dopante lleva a una menor conductividad iónica de oxígeno y a temperaturas superiores a 1000 K, una mayor conductividad electrónica de tipo p. El número de transferencia del ión oxígeno en aire fue determinado y varía en el rango 0.78 a 0.96 disminuyendo con el aumento de x y de la temperatura. El coeficiente de expansión térmico de las muestras cerámicas de LaGa0.85-xMg0.15(Nb0.33Mg0.66)xO3-δ fue calculado en el rango de temperatura de 300 a 1100 k siendo independiente de la composición, y variando en el rango (10.0 ± 0.2) x 10-6 K-1. Los valores de la energía de activación para la conductividad eléctrica total en aire son 104-106 KJ/mol en el rango de temperatura 670-1000 K y 67-76 kJ/mol en el rango de temperaturas 1000-1200 K. Se encontró que el método de síntesis afecta tanto a la simetría de la celda unidad de la red perovskita como a la composición de fases. La presencia de fases secundarias lleva a la disminución dramática de la conductividad