Mechanical properties such as Young's modulus, shear modulus. Poisson's ratio and internal friction of conventional electrolyte materials for solid oxide fuel cells. Zr(0).(85)Y(0.15) O(1.93) (YSZ). Zr(0.82)SC(0.18)O(1.91) (ScSZ). Zr(0.81)SC(0.18)Ce(0.01)O(2-delta) (ScCeSZ), Ce(0.9)Gd(0.1)O(2-delta) (GDC), La(0.8)Sr(0.2)Ga(0.8)Mg(0.15)Co(0.5)O(3-delta) (LSGMC), La(0.8)Sr(0.2)Ga(0.8)Mg(0.2)O(3-delta) (LSGM). were evaluated by a resonance method at temperatures from room temperature to 1273 K in various oxygen partial pressures. The Young's modulus of GDC gradually decreased with increasing temperature in oxidizing conditions. The Young's moduli of the series of zirconia and lanthanum gallate based materials drastically decreased in an intermediate temperature range and increased slightly with increasing temperature at higher temperatures. The Young's modulus of GDC considerably decreased above 823 K in reducing atmospheres in response to the change of oxygen nonstoichiometry. However, temperature dependences of the Young's moduli of ScCeSZ and LSGMC in reducing atmospheres did not show any significant differences with those in oxidizing atmospheres. (C) 2011 Elsevier B.V. All rights reserved.