Aluminum Oxide and the Opacity of Oxygen‐rich Circumstellar Dust in the 12–17 Micron Range

Abstract

Amorphous alumina (Al2O3) was produced by a sol-gel technique in order to make available its optical constants for possible astrophysical applications. Gradual annealing showed that the X-ray amorphousness of alumina ended somewhere between 723 and 873 K. Above this transition point, the structure changes into disordered γ-Al2O3. At T > 1273 K, crystalline α-Al2O3 (corundum) is formed.