Yttrium and gadolinium-doped ceria-based electrolytes (20 at% dopant cation) with and without small Ga(2)O(3)-additions (0.5 mol%) were fired at peak temperatures of 1250 and 1300 degrees C, or following a two-step sintering profile including one peak temperature and subsequent dwell at 1150 degrees 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 degrees 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. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.