A contrast of carbothermal reduction synthesis of MgAlON and AlON powders for transparent ceramics

Abstract MgAlON and AlON powders have been synthesized by carbothermal reduction and nitridation (CRN) from C–Al 2 O 3 –7.8 wt% MgO and C–Al 2 O 3 systems, respectively. The phase and morphology of the systems were investigated under 1100–1750 °C via XRD, DTA, SEM and NMR. The results showed that, MgO could significantly effected the stabilization region and morphology of the (Mg)AlON products. The formation of spinel MgAl 2 O 4s intermediate phase was key to obtain MgAlON at lower temperature with smaller particles than that of AlON. Under the optimized compositions, single-phase MgAlON and AlON were obtained at 1600 °C and 1720 °C, respectively. When sintered at 1850 °C for 24 h, the MgAlON sample was clear with highly transparency (82.5% at 3.7 μm), while AlON was opaque with lower transmittance (∼8.0% at 4.7 μm) due to lower sintering activity of the powder.