High-temperature compressive creep behaviour of the perovskite-type oxide Ba0.5Sr0.5Co0.8Fe0.2O3 – d

Compressive creep tests have been performed on perovskite-type Ba0.5Sr0.5Co0.8Fe0.2O3 − δ ceramics. The activation energy, stress exponent and inverse grain size exponent of the steady-state creep rates are evaluated at p(O2) = 0.21 ∙ 105 Pa and 0.01 ∙ 105 Pa in the stress, temperature and grain size ranges 5–20 MPa, 1078–1208 K and 2.5–17.4 µm, respectively. The results indicate that the creep rate of Ba0.5Sr0.5Co0.8Fe0.2O3 − δ is controlled by diffusion of cations via both the oxide lattice (bulk diffusion) and along grain boundaries. The creep rate of Ba0.5Sr0.5Co0.8Fe0.2O3 − δ increases profoundly by more than one order of magnitude at 1153–1178 K, which is tentatively linked with the onset of the hexagonal-to-cubic phase transition in this compound