Effect of cooling rate on the microstructure and luminescence properties of Sr2MgSi2O7:Eu2+,Dy3+ materials

Sr2MgSi2O7:Eu2+,Dy3+ long afterglow materials were prepared by a high-temperature solid-state reaction method with different cooling rates. The cooling rate had a slight effect on X-ray diffraction patterns and photoluminescence performance, but significantly modified the grain boundaries and long afterglow properties of the Sr2MgSi2O7:Eu2+,Dy3+ materials. When the cooling rate was 1 degrees C/min, grains remained intact with clear grain boundaries. As the cooling rate increased from 1 degrees C/min to 5 degrees C/min, some grain boundaries became indistinguishable. The afterglow properties were optimized, presenting best performance at the cooling rate of 3 degrees C/min. The trap state was investigated and illustrated through thermoluminescence curves. The depths of the traps of all the samples were unchanged, whereas densities changed to a large extent, leading to different afterglow properties. The retrapping process is discussed based on the afterglow curves.