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.

Impact of the electroforming process on the device stability of epitaxial Fe-doped SrTiO3 resistive switching cells

“…11,[33][34][35] The experimentally determined values of the activation energy vary between 0.86 and 1.005 eV.…”

First-principles calculations of the atomic and electronic structure ofFcenters in the bulk and on the (001) surface ofSrTiO3

“…29 Another aspect, which is of interest to many applications, concerns the mobility of O vacancies since this seems to be the mechanism responsible for the electrical behavior at low partial pressures. 17 Experiments performed at temperatures high enough so that F centers are supposed to have released their electrons, suggest a value of 0.86 eV for the migration energy in the bulk 17 whereas semiempirical shell model calculation for the empty vacancy predicts a smaller although close enough value of 0.76 eV. 28 The theoretical study of isolated single defects is not only nontrivial and time consuming but still remains of primary importance, since in most of experiments defect concentrations are quite low, whereas typical calculations are performed for unrealistically high defect concentrations which do not permit a direct comparison with experiments.…”

Defect mechanisms of coloration in Fe-doped SrTiO3 from first principles

“…3,12,[18][19][20][21] These models then adjust the ionization of the Fe dopant until predictions fit a measured physical property. Nevertheless, a number of EPR studies have detected the presence of a first nearest neighbor iron oxygen vacancy complex, which suggests this interaction is non-negligible.…”