Comparison of the chemical diffusion of undoped and Nb-doped SrTiO3

The re-equilibration kinetics of single crystal and thin films of SrTiO3 were monitored by measuring electrical conductivity as a function of temperature, T, and oxygen partial pressure, p(O2), over the ranges: 823 K < T < 1173 K and 10 Pa < p(O2) < 0.1 MPa, Application of the solution of Fick's second law (with the initial condition: no concentration gradient in specimen and the boundary condition: surface concentration constant) to the kinetic data gave the chemical diffusion coefficient for both oxidation and reduction runs. The chemical diffusion coefficient of thin films (both undoped and Nb-doped SrTiO3) exhibits ca. six orders of magnitude lower values than those of single crystal. This difference was considered in terms of different defect structure of the studied materials. (C) 1999 Elsevier Science Ltd. All rights reserved.