Barium aluminosilicate (BAS) powders have been synthesized by the sol-gel process. X-ray analysis and thermal analysis including differential thermal analysis (DTA), differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA) have been performed to characterize the powders. Also the effects of catalysts have been examined through an appropriate drying and sintering schedule for the formation of monoclinic celsian. It has been shown that the type of acid used as a catalyst controls the formation of polymorphs (hexagonal vs. monoclinic) of BAS ceramic. Because synthesis of monoclinic celsian by the sol-gel process requires relatively low temperatures and no seed crystals, it is less expensive, more producible, and easier to scale up than other synthesis processes.