Defect-Induced Self-Reduction and Anti-Thermal Quenching in NaZn(PO3)3:Mn2+ Red Phosphor

Self-reduction behavior of doped activators and zero-thermal-quenching luminescence have received much more attention in the exploration of luminescent materials for phosphor-converted white light-emitting diodes. Here, a combination of the two properties is demonstrated in a Mn2+ activated red phosphor, NaZn(PO3)(3):Mn2+, synthesized by a high temperature solid state reaction in ambient atmosphere, which is free from thermal quenching until 250 degrees C. By combined first-principles calculation and experimental investigation, the self-reduction mechanism from Mn4+ to Mn2+ and the anti-thermal quenching are clarified. The unique properties originate from the cation vacancy defects and the thermally induced energy transfer from the defect energy levels to the Mn2+ 3d excited state centers. This result will deepen the understanding of the effect of the crystal defect on luminescent materials, as well as inspiring more exploration on defect control to develop novel high thermal stability phosphors for practical application.