X-ray storage phosphors, their properties and mechanism

X-ray storage phosphors doped with rare earth ions were synthesized and their properties with respect to applications were characterized. A simplified band model for the photostimulated luminescence (PSL) processes of Ce, Tb, Sm and Sm doped BaFX phosphors is proposed. For the PSL mechanism of divalent europium doped BaFX (XCl or Br) we found some special characteristics. On the basis of many experimental results we think that during photostimulation electrons are excited from F(X^-) centers to a higher energy level and prefer transfer through tunneling rather than via the conduction band to recombine with the trapped holes, thus giving rise to the characteristic luminescence of the doped divalent europium ions.