Advanced Effect of the Substitution of Zn²⁺ on the Solid-State Synthesis of Red Phosphor, High Temperature Phase NaMgPO₄:Eu²⁺

It is known that high-temperature phase (olivine structure) of NaMgPO4:Eu2+ (NMP:Eu2+) is a precious oxide phosphor suitable for LED devices, emitting red at 625 nm under blue excitation. However, mainly due to the stable glaserite structure in the wide range of low temperature, pure olivine-phase NMP:Eu2+ is obtained only by using melt-quenching and arc-imaging furnace so far, which is inconvenient for the purpose of mass-production or industry. Generally, a traditional solid-state method is simpler and pollution-free, which is more favorable in phosphor-industry. Here, it is found that when quite small amount of Zn2+ is substituted for NMP:Eu2+ in solid-state method, the purity of olivine phase is much improved and the luminescence intensity is significantly improved. For the Na(Mg,Zn)PO4:Eu2+ having new composition, crystal structure, optical properties, and color properties are investigated. The phase transition temperature before and after doping with Zn2+ are calculated by combining TG/DSC experimental measurements and first-principles calculations. In addition, other characteristics related to the phosphor, such as structure, morphology, luminescence lifetime, thermal quenching properties, and quantum efficiency, are also studied in detail. Finally, it is demonstrated that this phosphor can be utilized in various applications through the manufacturing of LED devices, fluorescent pigments, and plant growth.