Tracer diffusion and chemical diffusion of oxygen in acceptor doped SrTiO3

Oxygen tracer and oxygen chemical diffusion coefficients have been determin ed for single crystalline SrTiO3 under defined temperature (f), oxygen part ial pressure (p(O-2)), and acceptor (m(Fe)) dopant concentration (m(Fe)) co nditions. Oxygen tracer diffusion results were obtained (873 K less than or equal to T less than or equal to 1173 K, p(O-2)= 10(5) Pa) by means of O-1 8 isotope exchange with subsequent analysis of the O-18 in-diffusion profil es by secondary ion mass spectrometry (SIMS). In the case of chemical diffu sion an in situ and spatially resolved, optical relaxation technique was ap plied (673 K less than or equal to T less than or equal to 973 K, 10 Pa les s than or equal to P(O-2) less than or equal to 10(5) Pa). The dopant conce ntration in both experiments was varied between 4.3 X 10(18) cm(-3) less th an or equal to m(Fe) less than or equal to 4.9 X 10(19) cm(-3). The evaluat ion of (ex situ) tracer and (in situ) concentration profiles are shown to b e in excellent agreement with defect chemical calculations. In contrast to the tracer diffusion coefficients (D*) the chemical diffusion coefficients (D-delta) are sensitive to ionic-electronic (short-range) defect interactio ns (internal buffer effects influence the thermodynamic factor) caused by v alence changes of the redox-active Fe-doping. (C) 2000 Elsevier Science Ltd . All rights reserved.