Comparison between MgGa₂O₄:Mn²⁺ and ZnGa₂O₄:Mn²⁺ nanophosphors synthesized by glycothermal method

MgGa₂O₄:Mn²⁺ (MGM) and ZnGa ₂O₄:Mn²⁺ (ZGM) nanophosphors were synthesized in 1,4-butanediol by glycothermal method at 300°C for 2h. The optimum photoluminescence (PL) intensity of MGM at 0.5 mol% Mn is higher than that of ZGM at 3.0 mol% Mn. We discuss this reason from several points of view. Transmission electron microscopy reveals that the particle size of MGM is smaller than that of ZGM. The X-ray diffraction peaks of MGM are broader than those of ZGM. These results cannot explain the higher PL intensity of MGM. The electron paramagnetic resonance spectroscopy and the PL decay analysis reveal that the homogeneity of Mn²⁺ ions in MGM is higher than that of ZGM, resulting in the more efficient PL process for MGM. The high homogeneity of Mn²⁺ ions is possibly attributed to the formation of MGM from the low-crystallized glycoxide precursor with a homogeneous mixture of different metallic ions. In contrast, ZGM could be formed by the crystallization of ZnGa₂O₄, followed by the incorporation of Mn²⁺ ions into ZnGa₂O₄.