Abstract
Mn2+ is attracting increasing attention due to its potential application as an activated ion in the phosphors. In this study, a rare-earth free phosphor, LiMgBO3:Mn2+, was synthesized using a high temperature solid-state reaction. Combined with X-ray diffraction and PL/PLE as well as first-principles calculation, the coordination environment of Mn2+ was disclosed, revealing that Mn2+ ions were inclined to occupy two partially filled Li sites. Under 427 nm-excitation, an abnormal deep red emission band centered at 705 nm was observed. This was due to the strong crystal field environment of Mn2+ induced by the extremely distorted five-coordinated sites, which was proved by the electronic band structure obtained from the density functional theory calculations. In addition, the luminescence intensity and thermal stability of LiMgBO3:Mn2+ was significantly enhanced when Li+ was replaced by Na+ and K+. This study disclosed the origin of the abnormal luminescence of Mn2+ in LiMgBO3 and further enriched our understanding of the abnormal luminescence of Mn2+ in special crystal structures (five-coordinated configuration).
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