Crystallization kinetics and densification of YAG nanoparticles from various chelating agents

Yttrium aluminium garnet (YAG, Y3Al5O12) nanoparticles were prepared using sonochemical sol-gel method with three different chelating agents and the effect of crystallization kinetics was investigated with differential scanning calorimetry-thermogravimetry (DSC-TG). The activation energy values of crystallization for the as-synthesized YAG nanoparticles using citric acid (CA), glycine(G)ora mixture of citric acid-glycine (CA-G), as chelating agents were found to be 160.5,142.2 and 140.4 kJ mol(-1) and the corresponding Avarami constants were 2.2, 2.1 and 1.9, respectively. Samples produced with the mixed chelating agent under sonification, could be crystallized to single phase YAG nanoparticles (10-65 nm) after annealing at 1100 degrees C. Pellets made from the annealed YAG particles could be sintered to a relative density greater than 99% at 1500 degrees C with a grain size of 4.5 mu m, made up of secondary particles formed from primary nano-crystals within the grains. Grain size and relative density increased with different chelating agents from CA to G and CA-G in the increasing order when YAG samples were sintered. Grain growth and densification occurred at a relatively low temperature of 1500 degrees C as compared to over 1800 degrees C in solid-state reactions. (C) 2009 Elsevier Ltd. All rights reserved.