Combustion Synthesis And Luminescent Properties Of Ca,SrMoO₄ :Eu ³⁺Red Phosphor

Molybdate is an important light-emitting substrate material with excellent physical and chemical properties. At present, there are a lot of phosphor preparation methods, such as precipitation, thermal decomposition, sol-gel method, emulsion, laser evaporation condensation method, CVD method, hydrothermal method, the template assembly and so on. Combustion method has many advantages, such as the process is simple, synthesis process is short, synthesis temperature is low, the product of the synthesis of high purity, good uniformity of chemical composition, the product of more uniform particles and small, etc. Considering the advantages of combustion process and the researches on using this method to synthesize molybdate-based luminescent materials are very limited. The present paper focuses on using a combustion process to synthesize Ca_0.6Sr_0.4MoO₄:Eu³⁺ phosphor.Using molybdate as matrix, rare earth Eu³⁺ single doped luminescence material was prepared by combustion method. The modern analysis techniques such as XRD, SEM and PL spectra were used to measure the property of the luminescence material.The CaMoO₄ and CaMoO₄:Eu³⁺ phosphors were prepared by the combustion method respectively using citric as fuels. The role of Eu³⁺-doped in CaMoO₄, effect of combustion synthesizing temperature and holding time on crystal structure and luminescent propertie of the phosphor were discussed in this paper. The XRD patterns show that the high purity CaMoO₄ and CaMoO₄:Eu³⁺ were obtained in condition of temperature from 700°C to 900°C for 10 min respectively. The CaMoO₄ and the CaMoO₄:Eu³⁺ have the type of scheelite crystal structure which is of tetragonal system with a space group I41/a. The crystallinity of the crystals was increased with the raising of the combustion reaction temperature and holding time. Fluorescence spectra show that the CaMoO₄ has an exciting peak at 270 nm and an emission peak at 490 nm. The fluorescence spectra of the CaMoO₄:Eu³⁺ was composed by that of the CaMoO₄ and 4 emission peaks of Eu³⁺ including at 591nm, 616nm, 655nm and 700nm. The peak at 616nm is the main emission peak. The peak at 490nm was enhanced with the increasing of the temperature and the time, at the same time, with a decreasing of the 616nm peak. A red phosphor, Ca_0.6Sr_0.4MoO₄:Eu³⁺,yNa+, was prepared by combustion method. The effects of synthesis temperature, Eu³⁺ concentration and charge compensator on its luminescent properties have been investigated. The XRD patterns show that the Ca_0.6Sr_0.4MoO₄:Eu³⁺,yNa+ were obtained in condition of temperature from 800°C to 1100°C for 10 min respectively. The CaMoO₄ and the Ca_0.6Sr_0.4MoO₄:Eu³⁺,yNa+ have the type of scheelite crystal structure which is of tetragonal system with a space group I41/a. The crystallinity of the crystals was increased with the raising of the combustion reaction temperature. The photoluminescence spectra show that the phosphor has a main emission peak at 616 nm (satisfactory red performance), which can be effectively excited by ultraviolet (UV) (278 nm, 395 nm) light. The results showed that the phosphor prepared by combustion reaction at 900°C for 10min has a higher luminous intensity than the sample obtained by solid state reaction at the same temperature for 2 hrs. The optimum reaction conditions in molecular fraction are 12% Li⁺, 8% Eu³⁺ with reaction temperature 900°C.