Spectral radiative properties of three-dimensionally ordered macroporous ceria particles

Abstract

Radiative properties of spherical heterogeneous particles consisting of three-dimensionally ordered macroporous (3DOM) cerium dioxide (ceria) are numerically predicted in the spectral range 290-10,000. nm. The particles are 1000. nm in diameter, with interconnected pores of 330-nm diameter and a face-centered cubic lattice arrangement. Predictions are obtained by solving macroscopic Maxwell's equations using the discrete dipole approximation and the finite element method. The scattering and absorption efficiency factors as well as the asymmetry factor are determined as a function of the particle orientation relative to the direction of the incident plane wave. The scattering and absorption efficiency factors show significant dependence on the particle orientation in the spectral range 560-1000. nm. Compared to homogeneous ceria particles, 3DOM particles of the same diameter have a significantly reduced extinction efficiency for wavelengths greater than 560. nm. Approximating the 3DOM particles as a homogeneous sphere with properties calculated from an effective medium theory is also considered. This approach is shown to be valid only for wavelengths much greater than the pore size, which demonstrates that a detailed geometrical representation of the internal particle structure is essential to obtain accurate radiative characteristics of highly ordered nano-structured particles.