Red Persistent Luminescence and Trap Properties of Mg₂SiO₄: Mn²⁺, M³⁺ (M³⁺ = B³⁺; Al³⁺; Ga³⁺; In³⁺) Material

Persistent luminescence (PersL), also called long-lasting phosphorescence or simply afterglow, is a luminescence characterised by the emission of radiation from a few seconds to several days after the excitation source has been switched off. Over the past two decades, research on PersL materials, both in fundamental and applied physics, has developed rapidly; however, the explanation for the physical processes that cause afterglow still needs to be clarified. Today, PersL materials are used mainly for luminescent paints, safety signs and decorations. At the same time, research into using such materials in medicine, information storage, anti-counterfeiting technology, etc., is underway.

Currently, information on the long persistent luminescence materials with emission in the blue and green spectral range is widely available. In contrast, the number of publications on the afterglow in the red and near-infrared spectral range is considerably lower.

Within the framework of this research, Mg₂SiO₄: Mn²⁺; M³⁺ (M³⁺ = B3+; Al³⁺; Ga³⁺; In³⁺) materials were synthesised using solid state reaction synthesis. When excited with X-rays, the materials exhibited a broad Mn²⁺ PersL band with two maxima at approximately 625 nm and 730 nm. After cessation of irradiation, an afterglow of at least 6 hours could be observed.

The research focuses on the trap properties of the materials. It was concluded that at least three discrete trap levels with activation energies approximately between 0.4–1.6 eV were present in the samples. Additionally, co-doping with Al³⁺; Ga³⁺; In³⁺ ions improved PersL longevity of the Mg₂SiO₄: Mn²⁺ material.