The Irradiation Induced Valence Changes and the Luminescence Properties of Samarium Ions in Ba[sub 2]SiO[sub 4]

A -doped phosphor was prepared by high-temperature solid-state reaction. The reduction of to was achieved by X-ray irradiation on the as-prepared . With the increasing exposure time, the -luminescence tends to be stronger up to and then saturated. The ions with different site symmetries formed in were observed in the emission spectra due to the transition and the decay curves of the level at various temperatures . The at the different sites in showed different quenching temperatures. Three crystallographic sites were identified in below . However, only one site was left at temperature higher than . The mechanism involved in the conversion of to under X-ray irradiation was discussed on the base of the crystal structure, crystallographic site-distributions, charge compensations, the crystal field strength acting on , and the defects created by X-ray irradiation. The photostability of the was evaluated with the photobleaching by monitoring the luminescence due to the transitions under the excitation of laser. The results in this report give some necessary information for its possible applications for optical storage devices.