In order to develop cathode materials for intermediate temperature solid oxide fuel cell (IT-SOFC), (Ba0.5Sr0.5)(1-x)GdxCo0.8Fe0.2O3-delta (BSGCF: X = 0, 0.02, 0.05, 0.08, and 0.1) oxides were synthesized by sol-gel method. The effects of Gd-doping on the phase structure, thermal expansion coefficient (TEC), thermogravimetric (TG) and the electrical conductivity were investigated. All samples have cubic structure and the lattice shrinks with the increasing content of Gd3+. The TEC values of BSGCF are in the range of 20.7-22.4 x 10(-6) K-1 from 50 to 900 degrees C and the abnormal expansion phenomenon at the temperature range of 300-550 degrees C is observed in all these samples, which is related with the loss of lattice oxygen as proved by the TG result. The conductivity of BSGCF10 is three times as large as BSCF at 500 degrees C. While abnormal phenomenon of BSGCF for the x=0.05 is explained through the critical radius calculation. (C) 2011 Elsevier B.V. All rights reserved.