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Infrared anisotropy averaging in polycrystalline samples and resonant scattering: the example of YMnO3

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Detalhes bibliográficos
Resumo:The reflectance of ceramic YMnO3 formed by randomly oriented large crystallites (average size about 10 m) was measured at near normal incidence in the spectral range 100–1200 cm1. A calibration method was used in order to compensate for the effect of diffuse reflection on the surface of the sample. The spectrum was modelled by averaging the single-crystal reflectivity over all possible crystalline orientations. This anisotropy averaging method was found to adequately describe most of the spectrum, but failed in the regions where one of the principal refractive index became smaller than unity. We argue that these discrepancies are due to enhanced resonant scattering, and discuss the effect with the help of a simplified model of independent spheres based on the Mie theory of light scattering.
Autores principais:Vieira, J. G.
Outros Autores:Ribeiro, J. L.; Santo, O.; Tavares, P. B.
Assunto:Modelling of infrared spectra Optical constants Polycrystalline materials Light scattering
Ano:2012
País:Portugal
Tipo de documento:artigo
Tipo de acesso:acesso restrito
Instituição associada:Universidade do Minho
Idioma:inglês
Origem:RepositóriUM - Universidade do Minho
Descrição
Resumo:The reflectance of ceramic YMnO3 formed by randomly oriented large crystallites (average size about 10 m) was measured at near normal incidence in the spectral range 100–1200 cm1. A calibration method was used in order to compensate for the effect of diffuse reflection on the surface of the sample. The spectrum was modelled by averaging the single-crystal reflectivity over all possible crystalline orientations. This anisotropy averaging method was found to adequately describe most of the spectrum, but failed in the regions where one of the principal refractive index became smaller than unity. We argue that these discrepancies are due to enhanced resonant scattering, and discuss the effect with the help of a simplified model of independent spheres based on the Mie theory of light scattering.