Patent ID: 6913648

Claim:
A process for preparing crystals of a rare earth element-activated, alkaline earth metal fluorohalide based stimulable phosphor precursor having a basic constitutional formula (1) as follows: Ba 1-X M x II FX: yM I , zLn (1) wherein, M II represents at least on alkaline earth metal selected from the group consisting of Sr and Ca: M I represents at least one alkaline metal selected from the group consisting of Li, Na, K, Rb, and Cs; X represents at least one halogen selected from the group consisting of Cl, Br, and I; Ln represents at least one rare earth element selected from the group consisting of Ce, Pr, Sm, Eu, Gd, Tb, T, and Yb; and x, y, and z are respectively within the ranges of 0≦x≦0.5, 0≦y≦0.5, and 0<z≦0.2, the process comprising the steps of: (a) preparing a reactant mother liquor of an aqueous solution containing BaX 2 , a water soluble compound of Ln, a halide, a nitrate, nitrite, an acetate of M II if x in the basic constitutional formula (1) is not 0, and a halide, nitrate, nitrite, or acetate of M 1 if y in the basic constitutional formula (1) is not 0, wherein the solution has a BaX 2 concentration of no more than 2.5 mol/L if X is Cl or Br, and a BaX 2 concentration of up to 5.0 mol/L if X is I after all substances have been substantially dissolved in said aqueous solution; (b) maintaining the reactant mother liquor at 20 to 100° C. while stirring; (c) preparing a precipitate of crystals of the phosphor precursor by simultaneously adding an aqueous solution of an inorganic fluoride salt and an aqueous solution of BaX 2 to the reactant mother liquor, while maintaining the reactant mother liquor at 20 to 100° C., and measuring an ion concentration in the reactant mother liquor using an ion concentration measuring device such that the ion concentration in the reactant mother liquor is constant; and (d) separating the precipitate of crystals of the phosphor precursor.