Rare-earth phosphor materials have been investigated for several decades due to their high X-ray absorption coefficient and emission efficiency, but these materials tend to reveal lower resolution and packing density when fabricated in bulk. In this work, we investigated the BaFBr:Eu²⁺ micro/submicro/nano-crystal phosphor material prepared using a precipitation method, and we demonstrate the dependence of the optical properties of these phosphors on the annealing temperature and Eu²⁺ concentration. The optimum preparation conditions were determined to be an annealing temperature of 600 °C for 2 h and an Eu²⁺ doping concentration of 0.1 mol%, achieving a quantum yield of 53.19%. Furthermore, the average lifetime is 669 ns. In comparison with typical bulk phosphors, the shape and size distribution of the crystallites, which is about 100 nm on average, may improve the resolution and enhance the fluorescence performance. The results of this study thus offer a new strategy for the development of highly efficient storage phosphors.