Formation of beta aluminas in the system Li2ONa2OAℓ2O3

The LiAℓO2NaAℓO2Aℓ2O3 phase diagram for 1300°C and 1500°C is presented. A region in which mixtures of β- and β"−alumina exist has been identified at both 1300°C and 1500°C while an additional field of pure β"−alumina was found at 1500°C. The effect of the amount of lithia on the relative amounts of β- and β"−alumina is discussed. A new way of considering the 'ideal' β"−alumina structure and composition is proposed, viz as a detective, spinel-like solid solution phase with formula Na1−x Lix Al5O8 : 0.2 ≲ × ≲ 0.3.