X-ray powder diffraction of β-aluminas

The structure of the β-alumina mirror plane is investigated with a powder diffraction technique in several crystals: Ag β, dehydrated Na β and hydrated Na β. At 295 and 423 K, an Ag⁺ distribution is found which agrees with that reported in the literature. With increasing temperature from 423 to 879 K, the Ag⁺ fraction in the aBR (anti-Beevers–Ross) sites decreases from 0.34 to 0.15. Hydration of Na β-alumina crystals does not seem to cause an appreciable change in the Na⁺ distribution. Analysis of the reflection intensities gives the exact quantity of absorbed water.