April 2017

Due to their high oxygen storage capacity, ceria zirconia solid solutions (CexZr1-xO2) are frequently used in catalytic applications, such as the three-way catalytic exhaust gas converter. Recently, nanostructured ceria-zirconia-based materials also attracted much attention due to enhanced proton conductivity at low temperatures, whose origin is still under debate.To study the influence of humidity on the electrical transport processes, we use a model system based on ceria zirconia thin films prepared by pulsed laser deposition. In order to measure the conductivity of the thin films parallel to the surface, platinum interdigital electrodes (light grey structure) were prepared by photolithographic methods in the Micro- and Nanofabrication Lab (MiNa) at the Center for Materials Research. The image at the left shows the temperature-dependence of the total conductivity obtained from impedance measurements on a ceria zirconia thin film shown in the SEM image on the right. At low relative humidity, an enhancement of the total conductivity is observed only at low temperatures due to proton conductivity. At high relative humidity, a conductivity plateau forms within the temperature range between 400 °C and 30°C arising due to the formation of a water layer on the thin films. (Picture submitted by Matthias Kleine-Boymann)