EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Spectroscopic techniques are one of the key steps in the characterization of novel nanomaterials and composites. In the case of infrared spectroscopy, however, there is one particular challenge that complicates its application to these materials, compared to the simpler analysis of homogeneous media: the need to account for the influence of material topology in the effective electromagnetic response of the homogenized effective medium (matrix + inclusions). This means that obtaining the dielectric function of the material’s components is often a complex inverse problem, which leads to widespread use of simplified effective medium models with predefined topologies to facilitate the computation. Here we propose a more robust methodology, based on Bergman’s spectral representation with user-defined arbitrary topological features, to obtain accurate values for the dielectric functions for the components and the topological information describing their spatial arrangement. We illustrate the principles of this method by studying a simple case study of a compacted CeO2 nanopowder, where the matrix medium consists only of air. The obtained dielectric function of the 5-10 nm nanoparticles has been compared to its single-crystal counterpart, and differences have been linked to the effects of particle-size reduction in the lattice dynamics of the material. Complementary information has been obtained using other spectroscopic techniques (Raman, UV/VIS).