A modified solid-state reaction method for the formation of terbium aluminum garnet (TAG:Ce) powder was studied. The starting materials, which included terbium oxide (Tb4O7), boehmite and cerium chloride (CeCl3.7H(2)O), were pre-aged at pH 3. This pre-aging process helps to form the core-shell structure, which leads to the formation of TAG:Ce phosphor powder via a solid-state reaction more easily. The emission intensity at 551 nm of the product pre-aged at pH 3 is higher than that formed without pre-aging. (C) 2007 Elsevier Ltd. All rights reserved.