The alkali problem in the crystal structure of beta alumina

Abstract

The crystal structure of sodium beta alumina was reinvestigated by means of three-dimensional data. Of special interest was the less stable sodium-oxygen layer by which the spinel-like blocks of the structure are held together. The original structure determined by Bragg, Gottfried and West (1931) and by Beevers and Ross (1937) turned out to be fundamentally correct. A deficiency of sodium and oxygen was found however in the interlayer. This fact makes it possible now to understand the wide range of sodium concentration reported for this compound. Several cycles of least-squares refinement reduced the disagreement factor R for 181 reflections to a final value of 4.3%.