Effect of cooling rate on the microstructure and luminescence properties of Sr MgSi O :Eu ,Dy materials.

Sr MgSi O :Eu ,Dy 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 Sr MgSi O :Eu ,Dy materials. When the cooling rate was 1°C/min, grains remained intact with clear grain boundaries. As the cooling rate increased from 1°C/min to 5°C/min, some grain boundaries became indistinguishable. The afterglow properties were optimized, presenting best performance at the cooling rate of 3°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.