Compressive creep tests of Sr-3(Ca1.18Nb1.82)O9-delta mixed Perovskite fabricated by melt processing were conducted in Ar and air to determine the deformation rate and to estimate the diffusion coefficient. At 1300-1350 degrees C, the steady-state strain rate (<(epsilon)over dot >) could be expressed as <(epsilon)over dot >=A sigma(1.9 +/- 0.2)exp[(-670 +/- 94 kJ/mole)/RT] where A is a constant, a is the steady-state stress, R is the universal gas constant, and T is the absolute temperature. The data and microstructural observations indicated that the mechanism that controls plasticity is grain rotation associated with redistribution of the intercellular phase, accommodated by cell coalescence, due to diffusion and dislocations. (c) 2007 Elsevier B.V. All rights reserved.