The subsolidus phase equilibria in air for the Al2O3-CeO2-PbO and Al2O3-CeO2-RuO2 systems were studied with the aim of obtaining information on possible interactions between a CeO2-based solid electrolyte in solid-oxide fuel cells (SOFCs) and other oxides. No ternary compound was found in either of the systems. The tie line in the Al2O3-PbO-CeO2 system is between Al2Pb2O5 and the CeO2. (C) 2004 Elsevier Ltd. All rights reserved.