Tracer diffusion and chemical diffusion of oxygen in acceptor doped SrTiO3

Oxygen tracer and oxygen chemical diffusion coefficients have been determined for single crystalline SrTiO3 under defined temperature (f), oxygen partial pressure (p(O-2)), and acceptor (m(Fe)) dopant concentration (m(Fe)) conditions. 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-18 isotope exchange with subsequent analysis of the O-18 in-diffusion profiles by secondary ion mass spectrometry (SIMS). In the case of chemical diffusion an in situ and spatially resolved, optical relaxation technique was applied (673 K less than or equal to T less than or equal to 973 K, 10 Pa less than or equal to P(O-2) less than or equal to 10(5) Pa). The dopant concentration in both experiments was varied between 4.3 X 10(18) cm(-3) less than or equal to m(Fe) less than or equal to 4.9 X 10(19) cm(-3). The evaluation of (ex situ) tracer and (in situ) concentration profiles are shown to be 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 interactions (internal buffer effects influence the thermodynamic factor) caused by valence changes of the redox-active Fe-doping. (C) 2000 Elsevier Science Ltd. All rights reserved.