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

Abstract

In the present work the effect of cobalt oxide addition on the structural and electrical properties of strontium titanate is examined. The SrTi1−xCoxO3−δ (0≤x≤0.4) samples were synthesized according to solid state reaction method at 1150°C and sintered at 1400°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°C in air atmosphere, as well as in a wide range of oxygen partial pressures (pO2=1×10−19–0.21atm) at 900°C. The conductivity dependence on pO2 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.