Preliminary study of thermal properties of Al₂O₃-Yb₂O₃ glass microspheres

Binary ytterbium-aluminate glass microspheres with eutectic (79.4 mol. % Al2O3, 20.6 mol. % Yb2O3) composition were prepared by flame synthesis in methan-oxygen flame. The starting powder was prepared by sol-gel method in order to obtain homogenous glass particles with a narrow interval of particle size distribution. Prepared microspheres were studied by optical microscopy, scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and differential thermal analysis (DTA). According to the XRD, small portion of YbAG, α-Al2O3 and non-identified phase were present in glass microspheres after flame synthesis. From DTA records, temperatures of onset of crystallization (Tc) and temperature of maxima of the exothermic crystallization peak (Tx) were determined. High temperature X-ray diffraction analysis (HT-XRD) in temperature range 750-1200 °C with 2h and 4h isothermal holding time at temperatures 933 and 1044 °C was performed for preliminary study of thermal behaviour of prepared system