PROBLEM TO BE SOLVED : To provode a method for producing a rare earth silicate-based fluorescent substance having a high radiation absorption coeffcient, having high accelerated phosphorescence strength and activated by a rare earth element.
SOLUTION : This method for producing the fluorescent substance comprises (1) a step of heating a rare earth carboxylate together with an alkoxyalcohol to form a solution, (2) a step of adding compounds of a silicon alkoxide and an activator element A and, if necessary, an activator element L to the solution and mixing them to form a mixed solution, (3) a step of acting moisture on the formed mixed solution to form the mixed solution into a gel material and (4) a step of thermally decomposing the formed gel material, wherein the fluorescent substance is expressed by composition formula : LuxYyGdzSiOp : aA, bL (A is Ce, Pr, Nd, Sm, Eu or the like; L is Zr, Nb, Hf, Ta, Sn or the like; x, y, z, a and b each satisfy the following relations : x≥0, y≥0, z≥0, 1.5≤x+y+z≤2.2, 2×10-5
