Phase evolution of YAG powders obtained by gel combustion combined with field-assisted rapid synthesis technique

Yttrium aluminum garnet (YAG) nanopowders were synthesized by a novel method combining gel combustion and field-assisted rapid synthesis technique. It is noted that hexagonal YAlO3 (YAH) is formed first at 800–830 °C by crystallization from the amorphous, and completely transforms to YAG at about 925 °C. The grain size of YAG powders calcined at 925 °C for 3 min is about 60 nm. Moreover, the phase evolution due to different heat treatment methods was also investigated. The results indicate that the crystallization pathways are related to the atmosphere and heating rate. In air, YAG is directly crystallized from amorphous precursors without any intermediate phases. In an anoxic atmosphere, phase formation follows an amorphous-YAH-YAG route at a rapid heating rate, while the amorphous-YAH+YAG-YAG route is observed in the case of slow heating.