Layered GdBaCo(2-x)Ni(x)O(5+delta) (0 <= x <= 0.3) complex oxides were synthesized and investigated as cathodes for intermediate-temperature solid oxide fuel cell (IT-SOFCs). All compositions formed an orthorhombic double-perovskite structure after calcination at 1000 degrees C for 5 h. The thermal expansion coefficient (TEC) was effectively decreased due to the partial substitution of Ni for Co, but the cathodic polarization resistance slightly increased with the increasing Ni content. Among the tested oxides, the GdBaCo(1.7)Ni(0.3)O(5+delta) composition showed a fairly reduced TEC (15.5 x 10(-6) K(-1)) and reasonably low polarization resistances (e.g., 0.54 Omega cm(2) at 600 degrees C), which was considered as a promising candidate for IT-SOFCs. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.