Tracer diffusion and chemical diffusion of oxygen in acceptor doped SrTiO3

Abstract

Oxygen tracer and oxygen chemical diffusion coefficients have been determined for single crystalline SrTiO3 under defined temperature (f), oxygen partial pressure (p(O2)), and acceptor (Fe) dopant concentration (mFe) conditions. Oxygen tracer diffusion results were obtained (873K≤T≤1173K,p(O2)=105Pa) by means of 18O isotope exchange with subsequent analysis of the 18O 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 (673K≤T≤973K,10Pa≤p(O2)≤105Pa). The dopant concentration in both experiments was varied between 4.3×1018cm−3≤mFe≤4.9×1019cm−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 (Dδ) 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.