Trapping Centers in CaS:Bi[sup 3+] and CaS:Eu[sup 2+],Tm[sup 3+]

Luminescence, excitation spectra, and decay curves of afterglow of the phosphors of and with and without co‐doping of were investigated. It was found that co‐doping monovalent ion could efficiently reduce the afterglow and the persistent time in both samples. The results imply that the trapping centers responsible for afterglow are defect‐related in both samples. Based on these results, it was expected that co‐doping any trivalent ions, such as and , into to substitute could produce charge defects and create trapping centers. Acquisition of strong afterglow and long persistent time in and is a strong support for the conclusion.