This work is centered on the comparative analysis of oxygen ionic conductivity, electronic transport properties and thermal expansion of solid electrolyte ceramics, providing a brief overview of the materials having maximum potential performance in various high-temperature electrochemical devices, such as solid oxide fuel cells (SOFCs). Particular emphasis is focused on the oxygen ionic conductors reported during the last 10-15 years, including derivatives of gamma-Bi4V2O11 (BIMEVOX), La2Mo2O9 (LAMOX), Ln(10-x)Si(6)O(26)-based apatites, (Gd,Ca)(2)Ti2O7-delta pyrochlores and perovskite-related phases based on LaGaO3 and Ba2In2O5, in order to identify their specific features determining possible applications. The properties of the new ion-conducting phases are compared to data on well-known solid electrolytes, such as stabilized zirconia, delta-Bi2O3-based ceramics, doped ceria and LaAlO3. The compositions exhibiting highest ionic conductivity are briefly discussed. (C) 2004 Elsevier B.V. All rights reserved.