Thermal Conductivity in Nanocrystalline Ceria Thin Films

摘要

The thermal conductivity of nanocrystalline ceria films grown by unbalanced magnetron sputtering is determined as a function of temperature using laser-based modulated thermorefiec-tance. The films exhibit significantly reduced conductivity compared with stoichiometric bulk CeO_2. A variety of micro-structure imaging techniques including X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron analysis, and electron energy loss spectroscopy indicate that the thermal conductivity is influenced by grain boundaries, dislocations, and oxygen vacancies. The temperature dependence of the thermal conductivity is analyzed using an analytical solution of the Boltzmann transport equation. The conclusion of this study is that oxygen vacancies pose a smaller impediment to thermal transport when they segregate along grain boundaries.