Oxygen surface exchange studies in thin film Gd-doped ceria

Electrical conductivity relaxation measurements were performed on gadolinium doped ceria thin films to evaluate chemical surface exchange rate of oxygen (K-ex, cm/s) under reducing ambient. The measurements were performed under identical conditions in bulk and thin films as a function of thickness (35-440 nm), temperature (943-1158 K), and oxygen partial pressure (10(-21)-10(-12) atm) using a custom built small volume cell assembly. The K-ex in thin films is found to be over an order lower than for bulk samples. Segregation effects in thin films likely lead to near-surface carrier depletion thereby decreasing oxygen exchange rate.