~18O tracer diffusion in Nb and La doped SrTiO_3 single crystal material under oxidising conditions has been investigated by Secondary Ion Mass Spectrometry (SIMS). The oxygen transport is sensitive to the duration of a preceding annealing step which is necessary in order to establish thermodynamic equilibrium between the specimens (which are in a reduced state as received) and the surrounding oxygen partial pressure. The diffusion profiles exhibit surface ~18O plateaus of significant depth; the plateaus are the more pronounced the lower the donor content, and the longer the pre-annealing step are. There is no influence of the donor type (Nb~5+ or La~3+).
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