Crystallization of Y 2 O 3 –Al 2 O 3 Rich Glasses: Synthesis of YAG Glass-Ceramics

An yttria-alumina glass incorporating 4 wt % of SiO 2 was prepared by the use of an aerodynamic levitator equipped with a laser heating device. Upon post synthesis annealing, the glass is observed to exhibit crystallization below the glass transition temperature. In the current study, this unusual behavior is examined using powder X-ray diffraction and infrared spectroscopy to follow crystallinity and optical absorbance as a function of annealing treatment. Double-resonance 27 Al/ 29 Si NMR spectroscopy and synchrotron diffraction experiments demonstrate that Si cations are incorporated in the formed Y 3 Al 5 O 12 (YAG) crystals on the 4-fold coordination Al site during crystallization. This has important consequences on the resulting microstructure of the YAG glass-ceramics.