Oxygen tracer diffusion in Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-d)

摘要

BSCF samples with the degree of closed porosity greater than 5% were annealed in 18O enriched atmosphere within the temperature range 370-550 °C at 0.21 atm. Depth profiling was performed by sputtering small craters (up to 10x10 μm) within the individual single grains. Surface exchange kinetics were initially found to be slow and presumably inhibited by the formation of a passivation layer on the sample surface. High temperature pre-anneals (900-950 °C) changes the nature of this layer and enhanced ~(18)O incorporation in the BSCF ceramics. Fast bulk oxygen diffusion and surface exchange were then observed within the temperature range studied. The activation energies for ~(18)O tracer diffusion and surface exchange were 0.72±0.05 and 1.10±0.15 eV, respectively.^