In situ Raman monitoring of low-temperature synthesis of YAG from different starting materials

Low-temperature formation of yttrium aluminum garnet (YAG) from different starting materials, i.e., alkoxide-acetate, nitrates, and hydroxides by homogeneous precipitation, has been monitored up to 1200 degrees C using in situ Raman spectroscopy. YAG was formed at relatively low temperature around 800 degrees C by the alkoxide method, but at 1100 degrees C by the nitrate and the hydroxide methods. Formation of an intermediate hexagonal YAlO3 phase was observed for the oxide powders prepared by the latter two methods at about 1000-1100 degrees C, which hindered the lower temperature formation of YAG phase. Additional Raman and X-ray diffraction investigation revealed the presence of impurities and the difference of local homogeneity in the oxide powders prepared by the different methods. Highly homogeneous powders obtained by the alkoxide method enabled the direct and low temperature formation of YAG. (C) 1999 Elsevier Science B.V. All rights reserved.