Steady-state creep experiments were performed on polycrystalline samples at temperatures ranging from 850 to 970C, under various O partial pressures. The results were combined with an analysis of previous deformation studies and indicated that, contrary to previous conclusions, the activation energy was a function of the O partial pressure. There were 2 different temperature regimes, which were characterized by pressure-independent activation energies of 675 and 1100kJ/mol at low and high temperatures, respectively. This was explained in terms of the operation of 2 independent rate-controlling mechanisms. These were grain-boundary diffusion and lattice diffusion.

M.Jiménez-Melendo, A.R.De Arellano-López, A.Domínguez-Rodríguez, K.C.Goretta, J.L.Routbort: Acta Metallurgica et Materialia, 1995, 43[6], 2429-34