Afterglow mechanism and thermoluminescence of red-emitting CaS:Eu~(2+),Pr~(3+) phosphor with incorporated Li~+ ion upon visible light irradiation

摘要

This paper reports on the afterglow mechanism and thermoluminescence (TL) of a red-emitting CaS:Eu~(2+),Pr~(3+) phosphor with incorporated Li~+ ion upon irradiation by visible light (D_(65) lamp). In the TL glow curve of the CaS:Eu~(2+),Pr~(3+) phosphor, a TL peak was observed near 120℃. The luminescence center of the CaS:Eu~(2+) ,Pr~(3+) phosphor was the Eu~(2+) ion and the trap depth of the CaS:Eu~(2+) ,Pr~(3+) phosphor with the cation vacancy (Trap 1) which formed by incorporation of the Pr~(3+) ion was 0.202eV. A cation vacancy (Trap 2) was formed by incorporation of the Li~+ ion in the CaS:Eu~(2+),Pr~(3+) phosphor. In the TL glow curve of the CaS:Eu~(2+),Pr~(3+) phosphor with incorporated Li~+ ion, two TL peaks were observed near 120 and 200℃. The TL luminance of the CaS:Eu~(2+),Pr~(3+) phosphor with incorporated Li~+ ion increased with an increase in the initial Li/Ca atomic ratio. The two TL peaks moved to the high-temperature side with an increase in heating rate. The cation vacancy (Trap 2) calculated from the Hoogenstraaten method was 0.118eV. The afterglow time of the CaS:Eu~(2+) ,Pr~(3+) phosphor with incorporated Li~+ ion was prolonged by generation of a shallow trap.