Photostimulated process in CsBrCl:Eu2+: a promising image screen phosphor

CsBrCl and CsBrCl:Eu2+ have been grown by “Double Run Bridgman technique”. Optical investigations have been carried out on the samples. The formation of F(Br−) and F(Cl−) centers have been confirmed by optical absorption bands at 640 and 615 nm, respectively. The photoluminescence (PL) spectra for europium (100 ppm) doped CsBrCl samples give emission of europium at 442 nm. This 442 nm emission is due to the transition from T2g component of 4f65d configuration to the ground state 8S of europium. The emission due to the presence of impurities in the host lattice is detected by PL technique. The OH− impurity in the host lattice due to decomposition of the salt in open air gives out emission at 395 and 365 nm. The O2− emission is observed at 465 and 468 nm. Photostimulated luminescence (PSL) process is studied in the samples by exciting them at F-absorption wavelength after irradiation. No PSL is observed for the undoped CsBrCl samples grown in vacuum. The PSL of vacuum grown CsBrCl:Eu2+ samples for excitations at 640 nm [F(Br−)] and 615 nm [F(Cl−)] is observed at 420 nm. It is deciphered that both F(Cl−) and F(Br−) centers contribute to PSL. The two F-centers noticed in absorption are stimulated separately; the resulting PSL signal confirms the participation of F-centers in photostimulated process. The lifetime of the PSL emission for CsBrCl:Eu2+ is determined to be 0.69 μs. Application of the material as a prospective image screen phosphor is elaborated based on PSL results.