Synthesis of YAG phase by a citrate-nitrate combustion technique

A white precipitate is yielded on heating a solution of Y(NO3)(3) (equivalent to 8 wt.% Y2O3), Al(NO3)(3) (equivalent to 7 wt.% Al2O3 and molar ratio of 1:1.9378 for Y2O3 to Al2O3) and citric acid in isopropanol with a citrate-nitrate molar ratio of 0.098 to 60 degrees C, The dried precipitate is then combusted at 200 degrees C and produces a solid product (ash). X-ray powder diffraction patterns of the ash and its calcined forms show that the ash is amorphous and remains amorphous up to 600 degrees C. The ash starts crystallizing to form a YAG phase at 800 degrees C and completely transforms into YAG below 900 degrees C. A certain amount of YAM phase co-exists with the YAG phase between 850 degrees C and 900 degrees C. Finally at 900 degrees C, only the YAG phase exists. This combustion technique for synthesis of YAG phase can be used for incorporation of sintering additives in non-oxide ceramics such as Si3N4. (C) 1999 Elsevier Science B.V. All rights reserved.