Microwave processing of sodium beta alumina

The conventional processing of sodium beta alumina (SBA) which includes synthesis and sintering in order to obtain dense bodies for use as a solid electrolyte usually requires high temperatures (similar to 1873 K) and long holding times. A substantial amount of Na2O may be lost during such high temperature heat treatment, the consequence of which may be deleterious when SBA is used for device applications. To overcome this problem, the use of microwave as heating source for the processing of SBA was attempted in the present process. Preliminary investigations on commercial Na-beta-alumina bearing the composition NaAl11O17 were carried out and it was found that Na-beta-alumina was a very good absorber of microwaves. Following this, a microwave active precursor of MgO-stabilized Na-beta"-alumina was synthesized through a novel solution technique, which on compaction and exposure to microwaves yielded dense (94% theoretical) and phase-pure Na-beta"-alumina body. This paper presents the results of a direct single-step synthesis cum sintering of MgO-stabilized Na-beta"-alumina. (C) 2002 Elsevier Science B.V. All rights reserved.