Thermal conductivity control by oxygen defect concentration modification in reducible oxides: The case of Pr0.1Ce0.9O2−δ thin films

We demonstrate the impact on thermal conductivity of varying the concentration of oxygen vacancies and reduced cations in Pr0.1Ce0.9O2−δ thin films prepared by pulsed laser deposition. The oxygen vacancy concentration is controlled by varying the oxygen partial pressure between 1 × 10−4 and 1 atm at 650 °C. Corresponding changes in the oxygen non-stoichiometry (δ) are monitored by detecting the lattice parameters of the films with high-resolution X-ray diffraction, while the thermal properties are characterized by time-domain thermoreflectance measurements. The films are shown to exhibit a variation in oxygen vacancy content, and in the Pr3+/Pr4+ ratio, corresponding to changes in δ from 0.0027 to 0.0364, leading to a reduction in the thermal conductivity from k = 6.62 ± 0.61 to 3.82 ± 0.51 W/m-K, respectively. These values agree well with those predicted by the Callaway and von Baeyer model for thermal conductivity in the presence of point imperfections. These results demonstrate the capability of controlling thermal conductivity via control of anion and cation defect concentrations in a given reducible oxide.