A two-step heating strategy for low-temperature fabrication of high sinterability and fine MgAlON powder with MgAl2O4 as Mg source

Abstract

Based on the reaction sequence during synthesis of MgAlON powder by solid-state reaction, a two-step heating strategy is proposed to low-temperature fabricate fine MgAlON powder of high sinterability by using MgAl2O4 as Mg source, respectively together with AlON and Al2O3+AlN. By introduction of an additional dwelling at 1550 °C to the first heating step, more α-Al2O3 dissolve into the solid solution at this temperature. By this way, overlarge particles of Al2O3 by agglomeration could be avoided in the next heating step to enable fast full reaction at a lower temperature. By dwelling 30 min at 1550 °C followed by 60 min at 1700 °C, single phase MgAlON powders were successfully prepared by solid-state reaction of all the two batches. The fine MgAlON powder synthesized by MAS+Al2O3+AlN batch exhibited high sinterability as the MgAlON ceramics pressureless sintered by this powder at 1880 °C without dwelling showed a transmittance up to 68.3%. The phase assemblage and morphology evolution of the mixture during solid-state reaction were monitored, which verified the effectiveness of the proposed two-step heating strategy. The low synthesis temperature of the two-step heating scheme benefits to prepare pure MgAlON powder with small particle size.