NiO/NiAl2O4 composites with 50/50, 55/45 and 60/40 wt.%/wt.% ratios were prepared from Al2O3 and NiO powders to use as an external SOFC supports that were denoted as 50NO50NS, 55NO45NS and 60NO40NS, respectively. Effects of support compositions and firing rates for sintering and reduction on shrinkage, thermal expansion coefficient and electrical conductivity of the supports were studied. The cells with NiO/NiAl2O4//Ni-YSZHYSZ//Pt configuration were co-sintered at 1400 degrees C in air and reduced at 800 degrees C in H-2 by varying the firing rate of 1 degrees C min(-1) (coded as -1) and 3 degrees C min(-1) (coded as -3). A dense YSZ electrolyte was observed in 50NO50NS-3 and 55NO45NS-3 cells, while cracks and pores appeared in the YSZ layer for 60NO40NS-3 cell indicating the greater difference in shrinkage and TEC between 60NO40NS support and YSZ electrolyte. Crack formation was eliminated and a dense YSZ electrolyte was obtained when the firing rate was reduced to 1 degrees C min(-1), suggesting that the different shrinkage between supports and YSZ electrolyte during sintering process can be alleviated at this firing rate. The highest power density (106 mW cm(-2) at 800 degrees C) was thus obtained for 60NO40NS-1 cell due to a superior electrical conductivity of 60NO40NS support to 50NO50NS and 55NO45NS. (C) 2013 Elsevier B.V. All rights reserved.