Ba0.6Sr0.4Co0.9Nb0.1O3-delta,5 (BSCN)-xGd(0.1)Ce(0.9)O(1.95) (GDC) composites with various GDC contents (x = 0-40, wt%) have been investigated for their potential application in IT-SOFCs. The effects of GDC addition on thermal expansion and electrochemical performances were studied. Thermal expansion measurement indicates that thermal expansion coefficients (TECs) decrease with increasing GDC content; in addition, GDC plays a catalytic role during the process of low-temperature thermal-driven reduction of Co4+ to Co3+. Polarization resistance (R-p) measurement indicates that the proper addition of GDC improves electrochemical performance of BSCN cathode. The optimum GDC addition to BSCN cathode is 20 wt% with the lowest R-p of 0.042 Omega cm(2) at 700 degrees C. The maximum power density of a cell with BSCN-20GDC cathode on 300 mu m-thick GDC electrolyte achieves 460 -880 mW cm(-2) at 700-800 degrees C. The excellent electrochemical performance of BSCN-20GDC composite cathode is ascribed to its much finer microstructure and larger cathode/electrolyte/gas triple phase boundary (TPB) areas. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.