Afterglow performance enhancement and mechanism studies on Y_2O_2S:Eu,Mg,Ti prepared via cold isostatic pressing

摘要

A Y_2O_2S:Eu,Mg,Ti material was prepared via a modified sulphide-fusion route. Compared with the tradi tional solid-state reaction method, the obtained Y_2O_2S:Eu,Mg,Ti showed smaller, more uniform particles with higher brightness. The afterglow mechanism study indicated that the long-afterglow material is process-dependent and that its performance is determined by recipe, preparation technology and process used. The luminescence centres of Y_20_2S:Ti; Y_2O_2S:Eu,Ti and Y_2O_2S:Eu,Mg,Ti are Ti~(4+) ions, Ti~(4+) + Eu~(3+) ions and Ti~(4+) + Eu~(3+) ions, respectively. The afterglow decay curve cannot be fitted using the exponential equa tion or first-, second-, third-order exponential decay multiple equations beyond 30 min. The afterglow luminescence of the materials resulted from Ti-related defects that make up two new trap levels. Ti dop ing created numerous harmful companying defects that decrease luminescence efficiency. Doping of Mg~(2+) ions facilitated the introduction of Ti~(4+) ions into the Y_2O_2S lattice to effectively modulate the depth and concentration of the trap. Doping of Mg~(2+)Ti~(4+) ion pairs reduced the number of harmful defects through the formation of a compensation-type hetero-valent substitution solid solution that greatly enhance the afterglow performance. Cold isostatic pressing promoted the entry of Ti ions into the Y_2O_2S crystal lattice and eliminated defects, such as preferred orientation. In addition, cold isostatic pressing reduced the E_2 to 0.9 eV, which is beneficial to the long afterglow of the resulting material at room temperature.