Linking the Electrical Conductivity and Non-Stoichiometry of Thin Film Ce<sub>1−x</sub>Zr<sub>x</sub>O<sub>2−δ</sub> by a Resonant Nanobalance Approach
Iurii Kogut,
Alexander Wollbrink,
Carsten Steiner,
Hendrik Wulfmeier,
Fatima-Ezzahrae El Azzouzi,
Ralf Moos,
Holger Fritze
Affiliations
Iurii Kogut
Institute of Energy Research and Physical Technologies, Clausthal University of Technology, 38640 Goslar, Germany
Alexander Wollbrink
Institute of Energy Research and Physical Technologies, Clausthal University of Technology, 38640 Goslar, Germany
Carsten Steiner
Department of Functional Materials, Bayreuth Engine Research Center (BERC), University of Bayreuth, 95440 Bayreuth, Germany
Hendrik Wulfmeier
Institute of Energy Research and Physical Technologies, Clausthal University of Technology, 38640 Goslar, Germany
Fatima-Ezzahrae El Azzouzi
Institute of Energy Research and Physical Technologies, Clausthal University of Technology, 38640 Goslar, Germany
Ralf Moos
Department of Functional Materials, Bayreuth Engine Research Center (BERC), University of Bayreuth, 95440 Bayreuth, Germany
Holger Fritze
Institute of Energy Research and Physical Technologies, Clausthal University of Technology, 38640 Goslar, Germany
Bulk ceria-zirconia solid solutions (Ce1−xZrxO2−δ, CZO) are highly suited for application as oxygen storage materials in automotive three-way catalytic converters (TWC) due to the high levels of achievable oxygen non-stoichiometry δ. In thin film CZO, the oxygen storage properties are expected to be further enhanced. The present study addresses this aspect. CZO thin films with 0 ≤ x ≤ 1 were investigated. A unique nano-thermogravimetric method for thin films that is based on the resonant nanobalance approach for high-temperature characterization of oxygen non-stoichiometry in CZO was implemented. The high-temperature electrical conductivity and the non-stoichiometry δ of CZO were measured under oxygen partial pressures pO2 in the range of 10−24–0.2 bar. Markedly enhanced reducibility and electronic conductivity of CeO2-ZrO2 as compared to CeO2−δ and ZrO2 were observed. A comparison of temperature- and pO2-dependences of the non-stoichiometry of thin films with literature data for bulk Ce1−xZrxO2−δ shows enhanced reducibility in the former. The maximum conductivity was found for Ce0.8Zr0.2O2−δ, whereas Ce0.5Zr0.5O2-δ showed the highest non-stoichiometry, yielding δ = 0.16 at 900 °C and pO2 of 10−14 bar. The defect interactions in Ce1−xZrxO2−δ are analyzed in the framework of defect models for ceria and zirconia.
