Tuneable persistent luminescence of novel Mg3Y2Ge3O12 garnet.

In this work novel garnet persistent luminescence phosphor Mg 3 Y 2 Ge 3 O 12 : Tb3+ (MYG: Tb3+) with bright blue to green tuneable emission is reported. MYG: Tb3+ samples with Tb3+ content ranging from 0 % to 100 % were analysed. X-ray absorption spectroscopy analysis showed that Tb3+ ions incorporate in the garnet structure by replacing Y3+ ions. Optimal dopant content was determined to achieve bright afterglow lasting more than ten hours. Tuneability of persistent luminescence was attributed to the deviations in populations of 5D 4 and 5D 3 emitting states of Tb3+ due to multiphonon relaxation and cross-relaxation processes. Photoluminescence, thermostimulated luminescence (TSL) and electron paramagnetic resonance (EPR) methods were used to determine the dominant persistent luminescence processes in the investigated material. The analysis of intrinsic defects in the material using EPR spectroscopy showed the presence of three distinct paramagnetic V-type centres and at least one F-type centre. The role of Tb3+ as a charge trap was discussed. MYG: Tb3+ exhibited luminescence tuneability by doping and temperature, which is promising for advanced anti-counterfeiting applications. • Blue to green tuneable persistent luminescence was achieved in Mg 3 Y 2 Ge 3 O 12 : Tb3+. • Tuneability results from deviation of population of 5D 3 and 5D 4 states of Tb3+. • Changes in population of the states is achieved by Tb3+ content and by temperature. • Introduction of Tb3+ in host suppresses the formation of paramagnetic hole centres. • The use of Mg 3 Y 2 Ge 3 O 12 : Tb3+ for anti-counterfeiting is demonstrated. [ABSTRACT FROM AUTHOR]