Impact of the Sintering Additive Al2O3 on the Electrical Conductivity of Proton-Conducting Electrolyte CaZr0.95Sc0.05O3 – δ

The impact of sintering additive Al2O3 on the electrical conductivity of calcium zirconate-based polycrystalline proton-conducting electrolyte CaZr0.95Sc0.05O3 – δ (CZS) is studied. With the sintering additive Al2O3, ceramic samples synthesized by a combustion technique are denser, and relatively low synthesis temperatures can be used (1470°C). Adding 0.1–0.5 wt % Al2O3 leads to an increase in the grain size from 100 nm to 1–2 μm. Increasing the Al2O3 content up to 0.3 wt % favors a growth in the electrolyte conductivity. For samples containing Al2O3, calcium aluminates are detected at grain boundaries. In samples exposed to humid air, charge transfer both in the grain bulk and at intergrain boundaries is found to be mediated by protons.