Temperature-dependent optical dispersion spectra for a single CeO₂ thin-film layer in UV-vis and its reflection and transmission in the IR region

CeO2 is a rare-earth refractory material with high refractive index, high thermal stability and infrared transparency; this knowledge can be utilized to develop practical thin films for high temperature thermophotovoltaics (TPVs) and thermal barrier coatings (TBCs). Here, we report ellipsometric measurements of a CeO2 thin film in the wavelength range 210 nm-2500 nm from room temperature to 500 C-circle. Because most previous spectroscopic studies of CeO2 evaluated its optical properties only at room temperature, our findings provide insights into the potential impacts of temperature change on the aforementioned applications, induced by the changes in its electronic structure. We also provide the reflectance and transmittance measurements of the same CeO2 thin film at room temperature using Fourier transform infrared (FTIR) spectroscopy. This knowledge can be leveraged to develop TPV and TBC designs. Finally, we used a software package called Stanford Stratified Structure Solver (S4) to simulate the angle-dependent reflectance spectrum. The optical properties of CeO2 films measured by ellipsometry are used as inputs to predict reflectance spectra. Comparison of the experimental FTIR reflectance with simulated reflectance in S4 shows strong agreement at three different angles.