Electrical and microstructural characterization of two-step sintered ceria-based electrolytes

Gadolinium-doped ceria-based materials with and without Ga-additions were prepared following several firing schedules including one peak sintering temperature (up to 1300 °C) with or without subsequent dwell at lower temperature (at 1150 °C). Sintered disks with submicrometric grain size and densifications in the order of 92% or higher, were obtained in this manner, with the final result depending slightly on the sintering profile and presence of Ga as dopant. All materials were characterized by scanning electron microscopy, X-ray diffraction and impedance spectroscopy in air, in the temperature range 200-800 °C. The grain boundary arcs were found slightly dependent on grain size and porosity but significantly on Ga-doping, due to the likely presence of large concentrations of Ga along the grain boundary region.