Influence of yttrium dopant on the synthesis of ultrafine AlN powders by CRN route from a sol–gel low temperature combustion precursor

Y-doped ultrafine AlN powders were synthesized by a carbothermal reduction nitridation (CRN) route from precursors of Al2O3, C and Y2O3 prepared by a sol–gel low temperature combustion technology. The Y dopant reacted with alumina and thus forming yttrium aluminate of AlYO3, Al3Y5O12 and Al2Y4O9, which formed a liquid at about 1400 °C and promoted the transformation of Al2O3 to AlN and the growth of AlN particles. Compared with the conventional solid CRN process, Y dopant reduced the synthesis temperature by 150 °C, and Al2O3 transformed to AlN completely at 1450 °C. The content of Y dopant had little effect on the synthesis temperature of AlN whereas it influenced the phase of Y compounds in the products. As the Y/Al molar ratio was in the range of 0.007648–0.022944, the particle sizes of Y-doped AlN powders synthesized at 1450 °C were 150–300 nm.