Insights into the element gradient in the grain and luminescence mechanism of the long afterglow material Sr2MgSi2O7: Eu2+, Dy3+

In the long afterglow luminescent material, the defects play an important role on the afterglow performance, but the understanding of the traps are still not uniform. In this research, the long afterglow material Sr2MgSi2O7: Eu2+, Dy3+ is treated by the acid corrosion liquid with different times to research gradient distribution of elements from outside to inside the grain of the long afterglow materials, the effect of the gradient on the structure, photoluminescence performance, long afterglow properties as well as the mechanism of luminescence are discussed. When the grain surface is destroyed, the initial brightness falls sharply, but the decrease of decay times are not obvious, that is caused by the different distribution of defects. The amounts of element Sr and O increase, but the Eu and Dy decrease from the outside to the inside the grain, the aggregate defects (V(O)over dotV '' Eu-Sr(Sr)n) or (2Dy((S)over dotr)V '' Eu-Sr)(n) which act as shallow traps are proposed, and meanwhile the isolated defects V-(O)over dot, Dy-(S)over dot r and V ''(Sr) act as deep traps. A new luminescent model is put forward to account for the long afterglow photoluminescence phenomenon, the shallow traps and the deep traps play different roles on the long afterglow properties, and most of the problems that exist in the long afterglow materials can be explained by this model. (C) 2018 Elsevier B.V. All rights reserved.