Depending on the alumina precursor used during beta-alumina synthesis, phase-pure and relatively stable beta"-alumina can be prepared both in the binary and the ternary compositional range. In addition, higher-indexed beta-alumina species beta"’ and beta(IV), which show a relation to beta- and beta"-alumina respectively, can also be prepared. Alumina precursors exhibiting a cubic-close-packed (gamma) oxygen sublattice, lead to the direct formation of the beta"-alumina family, whereas precursors with a hexagonal-close-packed oxygen ion array (alpha) form beta-alumina. K-beta"-alumina forms between 1100 and 1200 degrees C. Ternary K-beta"-alumina is stable until it decomposes into spinel, corundum and K2O vapor at 1900 degrees C.