Gadolinium-doped ceria-based materials with and without Ga-additions were prepared following several firing schedules including one peak sintering temperature (up to 1300 degrees C) with or without subsequent dwell at lower temperature (at 1150 degrees C). Sintered disks with subalicrometric 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 degrees 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. (c) 2008 Elsevier B.V. All rights reserved.