A 2D segment model for a solid oxide fuel cell (SOFC) with a mixed ionic and electronic conductor (MIEC) as electrolyte is developed, considering the mass transport, electrochemical reaction and charge transport. The electrochemical reaction is described by the Butler-Volmer equation and the expression of the oxygen partial pressure at the reaction interface is obtained by the energy conservation analysis. The model results are compared with experimental data and good agreement is achieved. The characteristics of the SOFC with a samaria doped ceria (SDC) electrolyte are analyzed by this model. Parametric simulations are conducted to investigate the uniformity of the leakage current (electronic current) and oxygen partial pressure in the electrolyte under various operating conditions. The results provide fundamental information on the leakage current in a SOFC and can serve as a useful tool for design optimization. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.