The Research On The Combustion Synthesizing Of SrMoO₄:Eu³⁺ Red Phosphor

Molybdate of Scheelite type crystal structure has special properties, can beexcited effectively blue and violet light, then transfer the excitation energy to the rareearth ions doped therein, make it become luminescent center. Alkaline earth metalmolybdate phosphors doped with trivalent europium ion has two strong excitationpeaks at395nm （near ultraviolet light） and465nm （blue light）, and it well match thecurrent mainstream white LED chips. Therefore, alkaline earth metal molybdate redfluorescent powder has become the research focus of red fluorescent powder for whitelight LED.Alkaline earth metal molybdate phosphors are prepared mostly by solid-statereaction method and sol-gel method at present, of which synthesis temperature andenergy consumption are high, Otherwise, sol-gel method is long-time and low-yield.While combustion synthesis method is rarely reported, of which synthesis is rapid,energy consumption is low.In this study, SrMoO₄:Eu³⁺red fluorescent powder was prepared by citricacid-assisted sol combustion method. Factors such as ignition-temperature, holding-time, Eu³⁺)concentration, charge compensation agent and combustion-supportingagent amount, whitch can affect illumination performance, have been studied. Thendetermined the optimization of process parameters of combustion synthesizingSrMoO₄:Eu³⁺). The results show that, SrMoO₄:Eu³⁺)red fluorescent powder preparedby combustion synthesis has excellent red luminescent properties. Excitationspectrum exhibit a broad band between200and350nm with a main peak at275nmand two stronger peaks at394nm （near ultraviolet） and465nm （blue light） respective.The emission spectra have a red emission peak with maximum at617nm. Thecrystallinization of synthetic product is increased with the increase ofignition-temperature and holding-time. On the basis of synthesizing SrMoO₄:Eu³⁺red fluorescent powder, We continuedto further synthesize red phosphor Sr1-x-2yMgxMoO₄:yEu³⁺,yM⁺（M=Li⁺, Na⁺, K⁺）,which co-doped by alkali metal ion and Mg²⁺. XRD analysis shows that, while thetemperature is700℃、800℃、900℃and1000℃, all synthetic samples are scheelitetype structure of tetragonal as the host lattice, but contain a little MgMoO₄witha.monoclinic crystal strcture. Fluorescence spectrum analysis shows that, thefluorescence powder can be excitated effectively by near ultraviolet at394nm andblue light465nm, then emit red light. Adding Mg²⁺can make the sample’s matrixlattice contract, and the position of main excitation peak of matrix shift to right. Asmall amount of Mg2+adding, can improve the luminous intensity of sample; butwhile Mg2+adding too much, it will reduce the luminous intensity of sample.Rerearch shows that, when the amount of Mg2+doped is0.3moles of MoO₄2-, theLuminous effect of phosphor powder synthesized by combustion method is good.Optimization of process parameters of combustion synthesizingSr1-x-2yMgxMoO₄:yEu³⁺,yM+fluorescent powder are: ignition temperature is900℃,holding time is40min, x=0.3, y=0.14, charge compensation agent is Li⁺, the moleratio of citric acid and MoO₄⁽2-is1.5:1. The synthetic product isSr_0.42Mg0.3MoO₄:Eu³⁺0.14, Li⁺0.14having good red fluorescence properties.