Anti-thermal quenching and self-reduction characteristics in Mn2+-doped LiScGeO4: Dual temperature effects on unique emission peak shifts

Mn-doped phosphors exhibiting self-reduction behavior have garnered significant attention in the study of luminescent materials due to the defects generated during the self-reduction process and their unique luminescent behavior. In this paper, LiScGeO4 red phosphors activated by the self-reduction of Mn4+ to Mn2+ were synthesized by high-temperature solid-state reaction in an air atmosphere. The defects generated during the selfreduction process were leveraged to attain exceptional anti-thermal quenching characteristics, with luminescent intensity at a high temperature of 430 K being 1.23 times compared to that at room temperature of 300 K. In addition, a peculiar phenomenon occurred where the emission peak initially blueshifts and subsequently redshifts with the increasing temperature. This study includes an analysis of the Rietveld-refined lattice parameters and surface micromorphology of the samples. The theoretical energy gap of the perfect LiScGeO4 matrix was calculated using density functional theory. Furthermore, the unique emission peak shift characteristics of Mn2+ were elucidated through the interaction between Mn2+ ions and the strength of the crystal field. Utilizing a defect model, the self-reduction mechanism and the anti-thermal quenching behavior were clarified. These findings will enhance the understanding of the effects of crystal defects and ion pair interactions on luminescent materials, and encourage further explorations of self-reducing phosphors to develop new high thermal stability phosphors for practical applications.