A comparative study of the synthesis of nanocrystalline Yttrium Aluminium Garnet using sol-gel and co-precipitation methods

Nanocrystalline yttrium aluminium garnet (nYAG) powder has been synthesized via sol-gel and co-precipitation methods using nitrate precursors. Thermal evolution and crystallisation kinetics of both the methods were investigated. The optimised calcination condition for the formation of nYAG was also examined. It was found that a complete transformation to nYAG was observed at 925 C/2 h and 1000 C/1 h for the coprecipitation and sol-gel samples respectively. An intermediate YAlO₃ phase was formed at 900 C in all powders regardless of the synthesis methods. The powder morphologies obtained from TEM revealed very similar particle sizes for the two routes (20-30 nm); whilst the extent of agglomeration was higher for the sol-gel method. It was also observed that by controlling the pH in a narrow range, maintaining the precipitate processing temperature and dehydrating excess OH- ions in the precipitates using n-butanol treatment, the extent of agglomeration was further reduced in the co-precipitated nYAG powder.