Abstract
Calcium sulfide singly and/or codoped with Eu2+, Ce3+ and Tm3+ phosphors were prepared by using a solid state chemical reaction method. Emission and excitation spectra of the samples were investigated. CaS:Eu2+ emission was found at 648 nm and CaS:Ce3+ emission was found at 515 nm. CaS:Eu2+,Tm3+ was long persistent and the persistence time was ~1 hour. By the doping Ce3+, CaS:Eu2+,Tm3+,Ce3+ persisted 22% longer than that of CaS:Eu2+,Tm3+. Strong energy transfer from Ce3+ to Eu2+ was found at a low doping concentration 0.1%. The brightness of Eu2+ emission was enhanced for about 20% by codoping with Ce3+.