The dynamic amplitude dependence of the Young's modulus and the internal friction of La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF6428) at high temperatures were evaluated by resonance measurements. At the temperatures from room temperature to 473 K and above 1073 K, the Young's modulus of LSCF6428 was independent of the dynamic amplitude, while it gradually decreased with increasing the dynamic amplitude in the temperature range from 573 to 973 K. The above dependence was successfully explained by considering the ferroelastic behavior of LSCF6428. (C) 2013 Elsevier B.V. All rights reserved.