Effect of strontium and lithium ions on afterglow time of red-emitting CaS:Eu~(2+), Pr~(3+) phosphor upon visible-light irradiation

摘要

This paper reports on the effect of the amount of Li~(+) and Sr~(2+) ions added to a red-emitting phosphor (CaS:Eu~(2+), Pr~(3+)) on afterglow time upon visible-light irradiation. The afterglow time of CaS:Eu~(2+). Pr~(3+) phosphor with Sr~(2+) ions (initial Sr/Ca atomic ratio of 0.10) was longer than that of the phosphor without Sr~(2+) ions by 20min. Moreover, the afterglow time of the Ca_(0.9)Sr_(0.1)S:Eu~(2+), Pr~(3+) phosphor with Li~(+) ions increased with an increase in the initial Li/Ca atomic ratio and was 146 min for an initial Li/Ca atomic ratio of 0.04. The lattice strain of the phosphor with both Sr~(2+) and Li~(+) ions showed a minimum value for this synthetic condition. The trap depths resulting from Li~(+) ion addition increased by about 0.145 eV. By adding both Li~+ and Sr~(2+) ions to the CaS:Eu~(2+), Pr~(3+) host, it was possible to improve the afterglow time.