As the substrate materials for segmented-in-series type solid oxide fuel cells (SOFCs), the mechanical characteristics, such as Young's modulus, of Al2O3-NiO-YSZ, TiO2-NiO-YSZ and MgO-NiO-YSZ were examined under SOFC operating conditions. The Young's modulus for all of the samples decreased at a high temperature. For the Al2O3-NiO-YSZ samples, the behaviours of the Young's modulus changed at each process including as-sintered, 100 h reduction and 2000 h reduction. For the TiO2-NiO-YSZ samples, the Young's modulus behaviour varied between the as-sintered and reduced samples. However, further reduction did not change the behaviour of the Young's modulus. For the MgO-NiO-YSZ samples, the Young's modulus of the samples exhibited a nearly constant behaviour through the sequence of processes from as-sintered to 100 h reduction and 2000 h reduction. Based on the microstructural analysis, the compositions of the framework of the samples and the sliding of the grain boundary strongly affected the Young's modulus. (C) 2013 Elsevier B.V. All rights reserved.