UV and X-ray excited red persistent luminescence in Mn²⁺ doped MgGeO3 material synthesized in air and reducing atmosphere

Materials with long persistent luminescence (PersL) have caused widespread interest among scientists and industry for decades. Currently, there is widely available information on the long persistent luminescence materials with emission in the blue and green spectral range, while the number of publications on the afterglow in the red and near-infrared spectral range is considerably lower. In the course of this work MgGeO₃ material doped with 0.1 mol% Mn²⁺ was produced using solid-state reaction synthesis in ambient and reducing atmospheres. The material exhibits a broad luminescence band with a peak around 680 nm, excited by either X-rays or UV. After cessation of irradiation, the afterglow up to 6 h when excited by UV and 15 h in the case of excitation by X-rays can be observed. Decay kinetics of the samples indicate that persistent luminescence in this material is a complex process that includes several different traps. Different thermally stimulated luminescence (TSL) techniques, such as T_stop – T_max and Hoogenstraaten's methods were employed to draw conclusions about the nature of the traps and properties of the material. It was concluded that multiple traps with activation energy between 0.60 and 1.55 eV are present in the samples, furthermore the synthesis in reducing atmosphere promotes creation of additional closely overlapping deep traps, which, based on electron paramagnetic resonance (EPR) measurements, most likely are related to oxygen vacancies.