The infrared dielectric properties of η–Al₂O₃

The infrared complex permittivity function of pseudo-cubic, disordered, spinel-type variety of alumina, η–Al₂O₃, obtained by spray pyrolysis, has been determined from its IR reflectance spectra, measured at near to normal incidence on pressed powder pellets. The optical constants obtained therefrom have been verified by using them in the simulation of the corresponding absorption spectra for KBr-diluted pellets of this material, and these are in excellent agreement with the experimental spectra. All calculations are based on a procedure for the estimation of the effective dielectric function of a mixture incorporating percolation features, which has been recently developed by the authors.