Phase evolution of yttrium aluminium garnet (YAG) in a citrate-nitrate gel combustion process

Yttrium aluminium garnet (YAG) powders were synthesized by a citrate-nitrate gel combustion process. Thermogravimetry (TG), differential thermal analysis (DTA), X-ray powder diffraction (XRD), and time-resolved X-ray powder diffraction experiments were used to study the phase evolution. Formation of the pure YAG phase depends on the level of precursor decomposition in the combustion process. Removal of undecomposed citric acid from the starting precursor powder helps to lower the temperature at which the YAG phase begins to form and the temperature at which the pure, highly crystalline YAG phase is obtained. The value of citrate to nitrate ratio in the precursor gel affects the phase evolution for YAG.