Visible and near-infrared optical properties of ceria ceramics

Visible and near-infrared properties of optically thick ceria ceramics encountered in solar-driven thermochemical cycles are determined in the wavelength range 0.35–2 μm by employing a novel methodology. The methodology consists of an analytical solution based on the modified two-flux approximation and the Monte Carlo ray-tracing method. The analytical solution is used to identify transport scattering albedo from normal-hemispherical reflectance of optically thick samples. The Monte Carlo ray-tracing method is used to obtain transport scattering coefficient in the near-infrared wavelength range 0.9–1.4 μm from bi-normal narrow-cone transmittance. Mie theory is employed to obtain transport scattering coefficient in an extended spectral range. Further, the index of absorption of ceria (cerium dioxide) is estimated by the additive relation for optically soft materials in a short-wave part of the near-infrared range. The proposed methodology is suitable for problems where traditional identification procedures have limited applicability because of highly scattering, optically thick materials and unknown index of absorption in the spectral range of weak absorption.