Chemical stability and electrical properties of BaCe0.85Y0.15O3−δ–Ce0.85Y0.15O2−δ composite bulk samples for use as central membrane materials in dual PCFC–SOFC fuel cells

• BaCe0.85Y0.15O3−δ and Ce0.85Y0.15O2−δ were synthesized using co-precipitation.
• Porosity affects the stability of BaCe0.85Y0.15O3−δ and Ce0.85Y0.15O2−δ composites.
• The composites maintain chemical stability in the presence of H2O at 600 °C.
• Morphology of the samples affects the electrical conductivity inside the materials.

The goal of the presented research was to determine the physicochemical properties of composite samples obtained by mixing BaCe0.85Y0.15O3−δ (BCY15) and Ce0.85Y0.15O2−δ (YDC15) in different ratios, and to achieve a better understanding of how these ratios affect the electrical conductivity, chemical stability and morphology of BCY15–YDC15 composite materials. It was determined that the samples are chemically stable in H2O-containing atmospheres at 600 °C. Furthermore, the porosity of the samples increases with the addition of YDC15 to BCY15. Both the porosity and the BCY15/YDC15 ratio affect the stability of the studied samples. The total activation energy (Et) values of the composite samples, determined via resistance measurements conducted in air at temperatures between 200 and 800 °C, are in the range of 0.590 ± 0.017 eV (Et of BCY15) to 1.132 ± 0.008 eV (Et of YDC15). This indicates that the properties of activation energy for composite materials are additive; the presence of both BCY15 and YDC15 affects the activation energy values. The different morphologies of the samples also influence the conductivity within the respective samples. The electrical conductivity values of the composite samples obtained at temperatures from 200 to 500 °C are in the order of magnitude of 10−7–10−3 S/cm. These values are between those determined for pure BCY15 and YDC15 at the respective measuring temperatures. Consequently, the materials show promise for application as porous central membranes (CM) in dual PCFC–SOFC fuel cells operating in the temperature range 600–700 °C.