A rapid combustion synthesis of MgO stabilized Sr- and Ba-β-alumina and their microwave sintering

MgO stabilized Sr- and Ba-β-alumina powders corresponding to the composition MMgAl10O17 (M=Sr or Ba) were synthesized through a rapid solution combustion route using stoichiometric amounts of metal nitrates and urea. The products were characterized by powder X-ray diffraction (XRD). The powders were compacted and sintered using microwaves as the energy source. Dense MgO stabilized Sr- and Ba-β-aluminas of 94% and 91%, respectively, were obtained within a short period of 30 min. AC impedance measurements on the microwave-sintered samples performed as a function of temperature yielded activation energies lower than that reported for the samples sintered through conventional routes. This paper reports of a novel method for synthesizing phase-pure powders of MgO stabilized Sr- and Ba-β-alumina and sintering of the powder compacts into dense membranes (>90% theoretical density) which materials are used as solid electrolytes in chemical sensors and molten metal processing.