Infrared Properties of Magnesium Oxide

Abstract

The absorption spectrum of polycrystalline and single‐crystal magnesium oxide was determined in the 4000 to 166 cm−1 spectral region. In the range 4000 to about 1100 cm−1, the absorption coefficient of the polycrystalline MgO was higher than that of the single‐crystal MgO owing to scattering by the grain boundaries. This scattering decreased with increase of the grain diameter. No difference in reflectivity could be detected between the polycrystalline and single‐crystal material in the 4000 to 300 cm−lwave number region. The optical constants, n and k, were determined by the classical dispersion theory, assuming a single oscillator. From the maximum reflectivity, the resonance frequency was at 428 cm−1; the value obtained from the acoustical vibration was at 475 cm−1. The corresponding s factors were 0.64 and 0.72, respectively.