Normal infrared spectral emittance of Al2O3

We have measured the near-normal ordinary ray transmittance and reflectance of crystalline Al2O3 from 1.6 micrometer to 11 micrometer and temperatures from 296 K to 582 K. The absorptance, or emittance, is derived from 1-(T+R), where T and R are the measured transmittance and reflectance. The derived emittance curves are compared with the predictions of a multi-phonon model prediction. Generally, good agreement is found between the measured and predicted results in the region of the multi-phonon absorption edge.