D1.2 - Temperature-Independent Resistive Oxygen Sensors Based on Sr[Ti,Fe]Ox Solid Solutions
- SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
- Proceedings SENSOR 2011
- D1 - High Temperature Sensors I
- R. Eichel - Universität Freiburg (Germany)
- 526 - 526
The mixed ionic-electronic conducting Sr[Ti,Fe]Ox solid-solution system is a promising candidate for oxygen sensors in lean burn engines owing to its strong sensitivity to oxygen partial pressure variations and negligible cross-sensitivity to temperature fluctuations. The underlying principles for sensing on an atomic scale are outlined. In particular, the electronic structure, defect chemistry, and transport properties are characterized and the impact of defect structure as function of oxygen partial pressure is analyzed by different spectroscopic techniques, such as Mössbauer and Electron Paramagnetic Resonance.
Based on these results a defect-chemical model is presented in which Fe is considered to be one of the main constituents that shape the energyband structure of Sr[Ti,Fe]Ox, rather than impurity dopants with acceptor-like character. As consequence of the high inherent deficiency in the oxygen sublattice, introduced by the mixedvalence states of the B-site cations Ti4+ and Fe3+, oxygen vacancies and interstitials generated by the anion Frenkel reaction dominate the defect equilibria, leading to predominant ionic conductivity at intermediate partial pressures of oxygen.