Single phase materials based on Co-doped SrTiO3 for mixed ionic-electronic conductors applications

In the present work the effect of cobalt oxide addition on the structural and electrical properties of strontium titanate is examined. The SrTi1-xCoxO3-delta (0 <= x <= 0.4) samples were synthesized according to solid state reaction method at 1150 degrees C and sintered at 1400 degrees C. The samples are single phase and crystallize in the cubic perovskite-type structure. With the increase of cobalt content the lattice parameter of the cubic cell is reduced, due to dimensional factor. The most dense sample is obtained for x = 0.2. The electrical conductivity is examined by 4-probe dc-technique in the range of 600-1000 degrees C in air atmosphere, as well as in a wide range of oxygen partial pressures (pO(2) = 1 x 10(-19)-0.21 atm) at 900 degrees C. The conductivity dependence on pO(2) can be explained by using the formalism of quasi-chemical reactions. The single-phase materials exhibit poor stability in reducing atmosphere (hydrogen) and good stability in salt-forming (carbon dioxide) components. In the oxidative region, the samples are characterized by mixed ionic-type conduction, and therefore can be used as membranes in high-temperature electrochemical devices; as for example, for oxygen production. The oxygen permeability and the thermal expansion measurements confirm that the specific materials can be used in electrochemical devices. (C) 2012 Elsevier B.V. All rights reserved.