Abstract
Platelike β-alumina particles with an average size of 0.3μm were formed at 1100°C from alkoxide-derived amorphous powder with the chemical composition (wt%) 9.3 Na2O, 1.0 MgO, and balance Al2O3. No β″-alumina formed from the gel of mixed alkoxides. The particle size of the β-alumina increased with increasing MgO content. Aggregation of the platelike particles in green compacts caused a tendency toward the formation of pores surrounded by flat planes, and pores of this type remained in the sintered samples. Densification of the β-alumina powders was inhibited by MgO, and Al2O3 dissociated from the β-alumina during sintering in an Na2O-poor atmosphere. The Na2O loss from green compacts in a semi-closed Pt container reached a constant value after a short sintering time and was suppressed in an Na2O-rich atmosphere. In addition, the evaporation behavior of MgO, measured during sintering at 1600°C, followed Henry's law in the MgO-Al2O3 system of β-alumina.
