Synthesis, densification and electrical properties of strontium cerate ceramics

Powders of pure and 5% ytterbium substituted strontium cerate (SrCeO3/SrCe0.95Yb0.05O3−δ) were prepared by spray pyrolysis of nitrate salt solutions. The powders were single phase after calcination in nitrogen atmosphere at 1100 °C (SrCeO3) and 1200 °C (SrCe0.95Yb0.05O3−δ). Dense SrCeO3 and SrCe0.95Yb0.05O3−δ materials were obtained by sintering at 1350–1400 °C in air. Heat treatment at 850 and 1000 °C, respectively, was necessary prior to sintering to obtain high density. The dense materials had homogenous microstructures with grain size in the range 6–10 μm for SrCeO3 and 1–2 μm for SrCe0.95Yb0.05O3−δ. The electrical conductivity of SrCe0.95Yb0.05O3−δ was in good agreement with reported data, showing mixed ionic–electronic conduction. The ionic contribution was dominated by protons below 1000 °C and the proton conductivity reached a maximum of ∼0.005 S/cm above 900 °C. In oxidizing atmosphere the p-type electronic conduction was dominating above ∼700 °C, while the contribution from n-type electronic conduction only was significant above ∼1000 °C in reducing atmosphere.