Chemical composition evolution of YAG co-precipitate determined by pH during aging period and its effect on precursor properties

The properties of YAG precursors aged at various pH levels for different aging times were examined to explore the influence of pH on the evolution of the chemical composition and the morphology of the precipitate, on the variation of phase composition during the calcination process. Precursors obtained at pH lower than 8.0 can be transformed into mono-phase YAG by calcination at low temperature, while those obtained at higher pH exhibit a variety of crystalline structures. Aging at high pH increased the impurity content of the calcined powder. Based on monitoring the pH during the precursor aging process, and the measurement of the Y/Al ratio in the precipitates, the mechanism of the chemical variation is discussed and the influence of pH and aging time on the synthesis of YAG precursor is discussed. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.