Partial Conductivities in SrTiO3: Bulk Polarization Experiments, Oxygen Concentration Cell Measurements, and Defect‐Chemical Modeling

Abstract

Knowledge of the exchange kinetics of O2 in SrTiO3 allows us to design appropriate strategies to separate the ionic and the electronic conductivity. In the low‐temperature range, where the overall surface reaction is very slow compared to bulk diffusion and measuring time, electrochemical cells of the type Pt|SrTiO3|Pt are self‐blocking and self‐sealing and a Wagner–Hebb‐type polarization succeeds without the necessity of using selectively blocking electrodes. In the present study the ionic conductivity data obtained for Feand Ni‐doped SrTiO3 in this way are compared to data obtained from the analysis of the oxygen partial pressure dependence of the total conductivity as well as to defect chemical calculations. In complete contrast to the low temperature situation, at high temperatures, where the surface reaction is fast, the emf technique is conveniently applicable. Results are presented for Pt, O2|SrTiO3|O2, Pt cells. The conductivity behavior of SrTi(Fe)O3 as a function of temperature (20°–1000°C) is complex, due to partially frozen‐in equilibria, but even details can be quantitatively understood in terms of a simple defect chemistry. The turnover of the diffusion‐controlled regime to the surface reaction‐controlled regime can be shifted to significantly lower temperatures by using YBa2Cu3O7–8 electrodes.