Theoretical and experimental evidences of defects in LiMgPO4

Abstract

The phosphate LiMgPO4 with orthorhombic olivine-type structure was synthesized by the conventional solid state reaction route and its optical properties were examined by the experimental and theoretical methods. Using diffuse-reflectance (DR) spectroscopy we observed two absorption stages at 5.5 eV and at 4.4 eV, which were attributed to the fundamental band gap and energy levels of defects within the band gap, respectively. These experimental results were confirmed by ab initio calculations. We observed photoluminescence and thermoluminescence (TL) in undoped LiMgPO4. Emission components were detected in the UV, visible and NIR regions. These multicolor emissions indicate the presence of various defects in LiMgPO4 and each color is due to different electronic transitions. The thermoluminescence of undoped LiMgPO4 shows that defects in LiMgPO4 serve as traps during irradiation. The TL glow curve with a sufficiently large light sum consists of five overlapping peaks in the temperature range 300–600 K.