Trapping processes in CaS:Eu2+,Tm3+

CaS:Eu2+,Tm3+ is a persistent red phosphor. Thermoluminescence was measured under different excitation and thermal treatment conditions. The results reveal that the charge defects, created by substituting Tm3+ for Ca2+, serve as hole traps for the afterglow at room temperature. Tm3+ plays the role of deep electron trapping centers, capturing electrons either through the conduction band or directly from the excited Eu2+ ions. These two processes, in which two different sites of Tm3+ are involved, correspond to two traps with different depths. (C) 2000 American Institute of Physics. [S0021-8979(00)05115-X].