Two-step sintering ceria-based electrolytes

Yttrium and gadolinium-doped ceria-based electrolytes (20 at% dopant cation) with and without small Ga2O3-additions (0.5 mol%) were fired at peak temperatures of 1250 and 1300 °C, or following a two-step sintering profile including one peak temperature and subsequent dwell at 1150 °C, 10 h. All materials were characterized by scanning electron microscopy, X-ray diffraction and impedance spectroscopy in air, in the temperature range 200–800 °C. Average grain sizes in the range 150–250 nm and densifications up to about 94% were found dependent on the sintering profile and presence of Ga. The grain boundary arcs in the impedance spectra increased significantly with Ga-doping, cancelling the apparently positive role of Ga on bulk transport, evidenced mostly in the case of yttrium-doped materials.