New synthesis of high-quality storage phosphors

We present a single step synthesis method for the photostimulable X-ray storage phosphor BaFBr:Eu2+ which results in a highly sensitive powder with a relatively small average grain size of 5.4 μm. The starting chemical reagents are BaCO3, NH4F, NH4Br and EuF3. The reaction initiated by the decomposition of the ammonium materials leads to highly volatile hydrogen halide gases which react with the BaCO3 to form BaFBr at temperatures up to 300 °C. Further heating results in the incorporation of Eu2+ and the formation of halide vacancies at temperatures in between 390 and 580 °C. The resulting photostimulated luminescence (PSL) efficiency is optimized after sintering at 800 °C. The reaction process is monitored by differential thermal analysis (DTA) and the reaction products are detected by mass-spectroscopy which confirms the proposed chemical reactions. Intermediate and final products are identified using X-ray diffraction. Photoluminescence (PL) and PSL spectra show the incorporation of Eu2+ into the lattice, as well as a PL peak at 470 nm which is not present in the PSL spectrum. This peak is shown to originate from O2− in the lattice and directly affects the PSL sensitivity.