Low-temperature synthesis of pure BaAl2Si2O8 glass–ceramic powder by citrate process

The citrate process was successfully used to prepare a glass–ceramic powder with the stoichiometric composition of BaAl2Si2O8 (BAS2). The solutions of barium and aluminum nitrate, colloidal silica, citric acid, and diethylene glycol were combined and afforded a clear gel on mixing which was further decomposed on heating to an easily handled precursor in a powder form. The characteristics of this dried precursor were analyzed by X-ray powder diffraction (XRD), differential thermal (DTA) and thermal gravimetric (TGA), and thermal mechanical analyses (TMA). An intermediate grinding of the precursor is crucial for the successful synthesis of the hexagonal BaAl2Si2O8 directly from the precursor which was crystallized at temperature as low as 850 °C for 4 h calcination.