Abstract
In this study, a dual phase composite (CSO-FC2O) consisting of 60 vol % Ce0.8Sm0.2O1.9 as oxygen-conductive phase and 40 vol % FeCo2O4 as electron-conductive phase was synthesized. TEM measurements showed a relatively pure dual-phase material with only minor amounts of a tertiary (Sm,Ce)(Fe,Co)O3 perovskite phase and isolated residues of a rock salt phase at the grain boundaries. The obtained material was used as a model to demonstrate that a combination of polarization relaxation measurements and Kelvin probe force microscopy (KPFM)-based mapping of the Volta potential before and after the end of polarization can be used to determine the chemical diffusion coefficient of the ceria component of the composite. The KPFM measurements were performed at room temperature and show diffusion coefficients in the range of 3 × 10−13 cm2·s−1, which is comparable to values measured for single-phase Gd-doped ceria thin films using the same method.
Highlights
Acceptor-doped cerium dioxide, where cerium is partially substituted by cations of lower valence, is a fluorite material with a very high oxide ion conductivity at comparably moderate temperatures
A dual phase composite (CSO-FC2O) consisting of 60 vol % Ce0.8Sm0.2O1.9 as oxygen-conductive phase and 40 vol % FeCo2O4 as electron-conductive phase was synthesized
The obtained material was used as a model to demonstrate that a combination of polarization relaxation measurements and Kelvin probe force microscopy (KPFM)-based mapping of the Volta potential before and after the end of polarization can be used to determine the chemical diffusion coefficient of the ceria component of the composite
Summary
Acceptor-doped cerium dioxide, where cerium is partially substituted by cations of lower valence (most prominently Gd3+), is a fluorite material with a very high oxide ion conductivity at comparably moderate temperatures (around 600 °C). It has already been in focus of research for roughly 50 years [1]. The ion conductivity is combined with a moderate electron conductivity, which strongly depends on the oxygen partial pressure [2,3,4] These features make ceria an interesting material for high-temperature industrial applications, for example, as oxygen permeation membrane, as oxygen sensor material, or for the use in solid oxide fuel cell components [1,5,6]. Apart from Gd-doped ceria, Sm-doped ceria could be an interesting alternative in this kind of composite due to its high ionic conductivity [17]
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